RU2848178C2 - Articles from polymer foam and methods of producing polymer foams - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to high-molecular compounds, specifically to moulded articles from foam and a method of producing said articles. Disclosed is an article made from thermoplastic polymer foam, having a continuous thermoplastic polymer matrix, which forms a plurality of pneumatic cavities along the entire length of the article. Surface area of the article extending for 500 microns (mcm) from the surface of the article includes compressed pneumatic cavities along its entire length.

EFFECT: invention enables to obtain large or thick-walled foamed articles having a continuous foam structure and thickness of more than 2 cm.

37 cl, 41 dwg, 32 tbl, 14 ex

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[ 0001 ] This application claims priority to U.S. Provisional Patent Application No. 62/867,516, filed June 27, 2019, and entitled "Method for Injection Molding Foamed Parts from Molten Foam." U.S. Provisional Patent Application No. 62/867,516 is hereby incorporated by reference as if fully set forth herein.

LEVEL OF TECHNOLOGY

Polymer foam products are widely used in industry due to their desirable properties of providing the high strength associated with solid polymer products, while also providing a reduction in density and, therefore, a reduction in the amount of polymer used to form a product of a given volume. Furthermore, the industry achieves advantages such as a reduction in the weight of the foamed product compared to its solid counterpart, while simultaneously receiving the advantages in strength, rigidity, impact strength, etc., which are provided by the polymer itself.

[ 0003 ] Thus, a number of non-traditional methods for introducing gas into thermoplastic polymers to form such foamed articles have been developed in the industry. To form an article from a foamed thermoplastic material using gas, according to commercial standards and industrial practice, a melt mixing device is used, which operates by maintaining pressure to limit the expansion of the gas within the device, while mixing the gas or a gas source with the thermoplastic polymer in the melt, furthermore, at a temperature above the melting point of the thermoplastic polymer. Such methods and devices are designed to minimize the formation of gas-filled voids (pneumatoceles, pneumoceles), or gas pockets that would otherwise be formed by the expansion of gas in the molten thermoplastic polymer. Thus, when contained within and positioned within a melt mixing device, the thermoplastic polymer may include a gas source or the gas itself, dissolved or dispersed therein, while not including pneumoceles or substantially not including pneumoceles. A mixture of a molten thermoplastic polymer and a gas at or above a temperature that would cause air voids to form at atmospheric pressure, but that does not contain air voids or is substantially free of air voids, may be called a molten pneumatic mixture. The temperature at which a gas, or pneumatogen, would cause air voids to form in a molten pneumatic mixture at atmospheric pressure may be called the critical temperature. Melt mixing devices, commonly known in the art, are thus designed and adapted for creating and metering molten pneumatic mixtures. Such devices are also suitable for producing molten pneumatic mixtures by adding a nascent, latent, or potential gas that is released at a characteristic temperature, or that results from an exothermic or endothermic chemical reaction at a characteristic temperature. The critical temperature of a nascent, latent, or potential gas is the temperature at which the reaction occurs or the gas is released into the thermoplastic polymer. All such materials and methods are well understood, and melt-mixing devices of various designs are readily available in industrial designs for this purpose. Traditionally used melt-mixing devices are single- or twin-screw extruders, modified to include a pressurized pressure chamber at the far end of the screw to receive a predetermined amount, or "injection material," of molten pneumatic mixture, which is expelled during mixing by the screw. This stimulates the movement of the molten pneumatic mixture toward the pressure chamber.

[ 0004 ] As a predetermined amount or injection material accumulates in the pressure chamber, the molten pneumatic mixture is metered from a melt mixing device and directed through fluidly communicating conduits, pipes, etc., into the mold cavity, thereby producing the desired shape. Typically, the metering is performed to maximize the degree of foaming (formation of air voids) that occurs in the mold cavity due to the reduction in pressure while the thermoplastic polymer is still molten. The expanded foam in the cavity is then cooled to form a foamed article. Foamed parts formed using this methodology are referred to in the industry as injection molded foams. These methods are generally limited to producing parts having thicknesses of approximately 2 cm or less.

[ 0005 ] Injection molding processes that utilize pneumatogen sources to create a foamed structure in molded parts can be understood from a recent review journal article by Bociaga et al., “The influence of foaming agent addition, talc filler content, and injection velocity on selected properties, surface state, and structure of polypropylene injection molded parts,” Cellular Polymers , 2020, Vol. 39 (Issue 1), pp. 3-30. In this publication, process conditions typically used for molding standard 4.1 mm thick ISO tensile test specimens by injection molding were systematically varied to create 16 different combinations of process settings and compositional variables (pneumatogen source concentration, filler content, injection rate, hold time, and hold pressure). The authors describe that adjusting the process conditions and compositions resulted in some changes in the foam structure of the resulting foamed parts, but all the different parts produced had a "skin layer," a term used in the industry to describe a dense, characteristic region near the surface of an injection molded foamed article that does not contain or is substantially free of air voids.

[ 0006 ] Examination of the surface of an injection-molded foam part and a region extending approximately 500 microns (µm) below the surface in any direction reveals a continuous thermoplastic zone—that is, a region that does not contain or is substantially free of air voids. Foamed parts formed by injection molding using traditional injection molding methods include a skin layer as a feature. Furthermore, the skin layer in most such parts is significantly thicker than 500 µm and can be 1 mm, 2 mm, 3 mm, or even thicker, depending on the methods, equipment, and materials used.

[ 0007 ] For the production of large foamed parts (such as pallets or wheelbarrow bodies), the above standard methods are unsuitable because the cavities of large molds experience excessive pressure drop as the molten air mixture enters and expands during mold filling, and air voids may form but then merge or leak from the viscous polymer flow during filling. Thus, in some cases, multiple-nozzle "structured foam" molding is used simultaneously to quickly fill large or thick mold cavities. In other situations, significant back pressure may be applied within the mold cavity to prevent air void formation during filling; the pressure may be released after the mold is filled, allowing air voids to form substantially within the mold cavity. Both approaches are often used in a single process.

[ 0008 ] However, the above methods for forming structured foam do not solve a problem that has seriously hampered the development of industrial production of very large parts. It is clear that the areas near the surface of the molten mass will cool much faster than its interior, and during cooling, a temperature gradient develops within the mass. The cooling rate in the deepest parts of the mass is the slowest. For large cavities of molds filled with a mass of molten polymer or pneumatic mixture, the interior of the mass can cool so slowly that the flow of the viscous thermoplastic material causes the resulting pneumatic cavities to coalesce, forming large polymer-free pockets and disrupting the desired continuous polymer matrix that forms such foams. This effect can be aggravated by shrinkage of the polymer in volume when it cools to a temperature below its transition temperature to the molten state. For large foamed parts, this effect can even lead to the complete destruction of the foam structure inside the part.

[ 0009 ] The overall reduction in strength and density associated with foamed articles does not occur without a continuous polymer matrix throughout the entire length of the article. Foamed articles that contain large polymer-free regions or voids degrade the structural integrity of the article, rendering such articles unsuitable for their intended use. These serious technical problems have limited the industrial use of polymer foams for many otherwise highly desirable applications. Accordingly, there is currently a pressing need to develop improved methods for producing foamed articles, particularly large or thick foamed articles. There is currently a pressing need to produce articles that have a continuous foam structure throughout their entire length. There is a particular need to produce articles that are greater than 2 cm thick and that have a continuous foam structure throughout their entire length. There is currently a need in industry to meet such needs using standard devices and materials.

ESSENCE OF THE INVENTION

[ 0010 ] A method for producing molten polymer foam is described herein. The method comprises: adding a thermoplastic polymer and a pneumatogen source to an extruder; heating and mixing the thermoplastic polymer and the pneumatogen source in the extruder under pressure to form a molten pneumatic mixture, wherein the temperature of the molten pneumatic mixture exceeds the critical temperature of the pneumatogen source; accumulating a quantity of molten pneumatic mixture in a collection zone of the extruder; creating a volumetric expansion in the collection zone to provide a pressure drop in the collection zone; allowing a period of time of expansion to expire after creation; and dosing molten polymer foam from the collection zone. In embodiments, the expansion volume is selected to be between 10% and 300% of the total expected volume of molten foam in the collection zone. In embodiments, the expansion period is between 5 seconds and 600 seconds. In embodiments, the molten pneumatic mixture is left undisturbed or substantially undisturbed during the expansion period.

[ 0011 ] In embodiments, the dosing is distribution into a forming element; in some embodiments, the forming element is a mold. In embodiments, there is fluid communication between the extruder and the mold. In embodiments, the dosing is a free flow of molten polymer foam. In embodiments, the dosing is a linear flow of molten polymer foam.

[ 0012 ] In embodiments, the method further comprises cooling the dosed molten polymer foam to a temperature below the transition temperature of the thermoplastic polymer into the molten state. In embodiments, one or more additional materials are introduced into the extruder, wherein the one or more additional materials are selected from colorants, stabilizers, clarifiers, nucleating agents, fibers, dispersed materials and fillers. In embodiments, the pneumatogen source is a pneumatogen, and the addition is injection under pressure. In other embodiments, the pneumatogen source includes bicarbonate, a polycarboxylic acid or its salt or ester, or a mixture thereof.

[ 0013 ] Also disclosed herein is a polymer foam article made using the methods, materials, and devices described herein. In embodiments, the polymer foam article has a foam structure throughout its entire length, characterized as a continuous polymer matrix that forms a plurality of air cavities therein. In embodiments, the surface region of the polymer foam article includes air cavities. In embodiments, the surface region is an area extending 500 microns (μm) from the surface of the article.

[ 0014 ] Also disclosed here are articles made of foamed thermoplastic polymer, wherein the article has a foam structure throughout its length, which is a continuous polymer matrix that forms a plurality of air cavities therein, furthermore, wherein a surface region of the article includes compressed air cavities. In some embodiments, the surface region is an area of the article that extends 500 microns (μm) from its surface. In some embodiments, the article includes compressed air cavities more than 500 microns (μm) from its surface. In embodiments, the article made of polymer foam has a thickness of more than 2 cm; in other embodiments, the article made of polymer foam has a volume of more than 1000 cm ³ , from 1000 cm ³ to 5000 cm ³ , or even over 5000 cm ³ ; and in still other embodiments, the polymer foam product has a volume greater than 1000 ^cm3 and a thickness greater than 2 cm, a volume between 1000 ^cm3 and 5000 ^cm3 and a thickness greater than 2 cm, or a volume greater than 5000 ^cm3 and a thickness greater than 2 cm.

[ 0015 ] In embodiments, materials used to produce polymer foam articles are not particularly limited and include thermoplastic polymers selected from polyolefins, polyamides, polyimides, polyesters, polycarbonates, polylactic acids, acrylonitrile-butadiene-styrene copolymers, polystyrenes, polyurethanes, polyvinyl chlorides, tetrafluoroethylene copolymers, polyether sulfones, polyacetals, polyaramids, polyphenylene oxides, polybutylenes, polybutadienes, polyacrylates and polymethacrylates, ionomeric polymers, block copolymers of polyethers and amides, polyarylether ketones, polysulfones, polyphenylene sulfides, polyamide-imide copolymers, polybutylene succinates, cellulosic materials, polysaccharides, and their copolymers, alloys, compounds and blends. In some embodiments, the thermoplastic polymer is a stream of mixed plastic waste. The continuous polymer matrix optionally further includes one or more additional materials selected from colorants, stabilizers, brighteners, nucleating agents, fibers, dispersed materials, and fillers.

[ 0016 ] Other purposes and characteristics will be partly obvious and partly specially noted below.

BRIEF DESCRIPTION OF DRAWINGS

[ 0017 ] FIGS. 1A-1B illustrate a melt mixing apparatus suitable for performing the methods described herein.

[ 0018 ] FIG. 2-1 is a photographic image of a part molded according to a standard foam molding method as described in Example 1. FIG. 2-2 is a photographic image of a part molded according to a molten foam injection molding (MFIM) method as described in Example 1. FIGS. 2-3 and 2-5 are photographic images of a section cut from a part molded according to a standard foam molding method as described in Example 1. FIGS. 2-2 and 2-3 are photographic images of a section cut from a part molded according to the MFIM method as described in Example 1.

[ 0019 ] FIG. 3A is a photographic image of a cross-section of Part A produced according to a standard foam molding method and cut into two pieces to expose the cross-section as described in Example 2. FIG. 3B is a photographic image of a cross-section of Part B produced according to the MFIM method and cut into two pieces to expose the cross-section as described in Example 2.

[ 0020 ] FIG. 4A is a photographic image of a cross-section of Part C produced according to the MFIM method and cut into two pieces to expose the cross-section as described in Example 2. FIG. 4B is a photographic image of a cross-section of Part D produced according to the standard foam molding method and cut into two pieces to expose the cross-section as described in Example 2.

[ 0021 ] FIG. 5 is a graph including curves of part density versus decompression volume for various decompression durations for Test B, as described in Example 3.

[ 0022 ] FIG. 6 is a graph including the strain-time curves for the parts obtained in Tests A, B, and C, as described in Example 4.

[ 0023 ] FIG. 7 shows photographic images of views in various aspects of Parts A, B and C, as described in Example 4.

[ 0024 ] FIG. 8 is a photographic representation of cross-sectional views of Parts A', B', C' and D' as described in Example 4.

[ 0025 ] FIG. 9 is an illustration of two parts as described in Example 5.

[ 0026 ] FIG. 10 is an isometric image obtained by tomographic scanning of a first part formed according to the MFIM method as described in Example 6.

[ 0027 ] FIG. 11 is an illustration of the cross-sectional plane shown in FIG. 10, as described in Example 6.

[ 0028 ] FIG. 12 is a graph including curves of average cell size and cell number versus cell roundness for the first part produced as described in Example 6.

[ 0029 ] FIG. 13 is a diagram of an X-ray tomographic image of a cross-section of the second (spherical) part, as described in Example 6.

[ 0030 ] FIG. 14 is a graph including curves of average cell size and cell number versus cell roundness for a second (spherical) part produced as described in Example 6.

[ 0031 ] FIG. 15 is a micrograph of the fracture surface of a cleaved three-inch (7.62 mm) diameter composite sphere produced by the MFIM method as described in Example 7.

[ 0032 ] FIG. 16 is a photomicrograph of the fracture surface of a cleaved three-inch (7.62 mm) diameter composite sphere produced by the MFIM method as described in Example 7.

[ 0033 ] FIG. 17 is a micrograph of the fracture surface of a cleaved three-inch (7.62 mm) diameter composite sphere produced by the MFIM method as described in Example 7.

[ 0034 ] FIG. 18 is a photomicrograph of the fracture surface of a cleaved three-inch (7.62 mm) diameter composite sphere produced by the MFIM method as described in Example 7.

[ 0035 ] FIG. 19 shows micrographs of cross-sections of ISO tensile test specimens prepared according to the standard foam molding method in Experiments 10, 11, 14, and 15, as described in Example 8.

[ 0036 ] FIG. 20 shows micrographs of cross-sections of portions of ISO tensile test specimens obtained by the MFIM method in Experiments 9, 10, 15, and 16, as described in Example 8.

[ 0037 ] FIG. 21 shows micrographs of a cross-section of a portion of the ISO tensile test specimen produced by the MFIM method in Experiment 9 and stress-strain curves in the re-produced MFIM parts in Experiment 9, as described in Example 8.

[ 0038 ] FIG. 22 includes a micrograph of a cross-section of a portion of an ISO tensile test specimen produced by the standard foam molding method in Experiment 10 and stress-strain curves in re-produced MFIM parts in Experiment 10, as described in Example 8.

[ 0039 ] FIG. 23 includes two X-ray tomographic images of a portion of an ISO tensile test specimen formed by the standard foam forming method in Experiment 15, as described in Example 8.

[ 0040 ] FIG. 24 includes two X-ray tomography images of a portion of the ISO tensile test specimen formed by the MFIM method in Experiment 9, as described in Example 8.

[ 0041 ] FIG. 25 is an X-ray scan image of a portion of a large tensile test specimen formed by the MFIM method as described in Example 9.

[ 0042 ] FIG. 26 includes cross-sectional views of eight large tensile specimens formed by the MFIM method as described in Example 9.

[ 0043 ] FIG. 27 includes an X-ray tomographic image of a portion of a large tensile test specimen formed by the MFIM method as described in Example 9.

[ 0044 ] FIG. 28 includes a series of X-ray tomography images at various depths within a portion of a tensile test specimen formed by the MFIM method and a series of images at various depths within a portion of a tensile test specimen formed by the standard foam molding method as described in Example 10.

[ 0045 ] FIG. 29 is a graph including a cell number versus depth curve for a portion of a tensile test specimen formed by the MFIM method and a cell number versus depth curve for a portion of a tensile test specimen produced by the standard foam molding method, as described in Example 10.

[ 0046 ] FIG. 30 is a graph including a cell circularity versus depth curve for a portion of a tensile test specimen formed by the MFIM method and a cell circularity versus depth curve for a portion of a tensile test specimen produced by the standard foam molding method, as described in Example 10.

[ 0047 ] FIG. 31 is a graph including a cell size versus depth curve for a portion of a tensile test specimen formed by the MFIM method and a cell size versus depth curve for a portion of a tensile test specimen formed by the standard foam molding method, as described in Example 10.

[ 0048 ] FIG. 32 is a photograph of Sample 20 obtained by the inverse MFIM method as described in Example 12.

[ 0049 ] FIG. 32 is a photograph of Sample 20 obtained by the inverse MFIM method as described in Example 12.

[ 0050 ] FIG. 33 is a photograph of Sample 10 obtained by the MFIM method as described in Example 12.

[ 0051 ] FIG. 34 is a photograph showing a cross-section of Sample 20 produced by the inverse MFIM method as described in Example 12.

[ 0052 ] FIG. 35 is a photograph showing a cross-section of Sample 10 produced by the MFIM method as described in Example 12.

[ 0053 ] FIG. 36 is a graph of cell number versus depth (distance from surface) for Sample 10 (MFIM) and Sample 20 (inverse MFIM), as described in Example 12.

[ 0054 ] FIG. 37 is a plot of cell size versus depth (distance from surface) for Sample 10 (MFIM) and Sample 20 (inverse MFIM), as described in Example 12.

[ 0055 ] FIG. 38 is a graph including the average stress versus strain curve for Sample 10 (MFIM) and the curve for Sample 20 (inverse MFIM) based on bulk modulus measurements as described in Example 12.

[ 0056 ] FIG. 39 is a graph including the average stress versus strain curve for Sample 10 (MFIM) and the curve for Sample 20 (inverse MFIM) based on flexural modulus measurements as described in Example 12.

[ 0057 ] FIG. 40 is a graph of stress-strain curves from bulk modulus measurements obtained on three metallocene polyethylene (mPE) materials of different densities formed by MFIM methods as described in Example 14.

[ 0058 ] FIG. 41 illustrates a mold configuration useful for performing the methods described herein.

[ 0059 ] Corresponding reference numbers indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[ 0060 ] Although the present invention makes reference to preferred embodiments, it will be understood by those skilled in the art that changes in form and detail may be made without departing from the spirit and scope of the invention. Various embodiments will be described in detail with reference to the drawings, in which like reference numerals represent like parts and assemblies throughout the views. Reference to various embodiments does not limit the scope of the claims appended hereto. Furthermore, any examples set forth in this description are not intended to be limiting, and only some of the many possible embodiments for the claims appended hereto are set forth.

[ 0061 ] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All publications, patent applications, patents, and other literature references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and are not intended to be limiting.

[ 0062 ] As used herein, " polymer matrix ," including "continuous polymer matrix,""thermoplastic polymer matrix,""molten polymer matrix," and the like, means a continuous/continuous solid or molten phase of a thermoplastic polymer or a quantity of solid thermoplastic polymer forming a continuous phase.

[ 0063 ] As used herein, " molten mixture " means a molten thermoplastic polymer or a mixture of molten thermoplastic polymers, optionally including one or more additional materials mixed with the molten thermoplastic polymer or mixture thereof.

[ 0064 ] As used herein, " molten pneumatic mixture " means a mixture of a thermoplastic polymer and a pneumatogen source in which the polymer is at a temperature above its melting point and the temperature of the mixture exceeds the critical temperature of the pneumatogen source, further characterized as being void-free or substantially void-free. The molten pneumatic mixture is under a pressure sufficient to prevent the formation of voids, or substantially prevent the formation of voids, or to cause the pneumatogen source to dissolve or disperse within the thermoplastic polymer either as a gas or as a supercritical fluid. "Substantially void-free,""substantiallyvoid-free," and similar terms in relation to a molten pneumatic mixture mean that while pressure conditions may be used to prevent the formation of voids in the molten mixture, defects, worn parts, and the like in the processing equipment may cause an unintended loss of pressure that will not generally interfere with the production and maintenance of the molten mixture at the proper pressure.

[ 0065 ] As used herein, " foam ", "polymer foam", "thermoplastic polymer foam", "molten foam", "molten polymer foam", and similar terms generally refer to a continuous/uninterrupted polymer matrix forming a plurality of air voids as a dispersed phase dispersed therein.

[ 0066 ] As used herein, the term " pneumatocele " means a discrete cavity defined by and surrounded by a continuous matrix of thermoplastic polymer.

[ 0067 ] As used herein, the term " pneumatogen " means a gaseous compound capable of defining pneumatogenous voids within a molten thermoplastic polymer matrix.

[ 0068 ] As used herein, the term " critical temperature " means the temperature at which a pneumatogen source forms a pneumatogen at atmospheric pressure.

[ 0069 ] As used herein, the term " pneumatogen source " means a latent, potential, or emergent pneumatogen added to or present within a thermoplastic polymer matrix, such as dissolved in the matrix and/or present therein as a supercritical fluid; or in the form of an organic compound that forms a pneumatogen as a result of a chemical reaction; or a combination thereof; or the pneumatogen source is a pneumatogen, becomes a pneumatogen, or forms a pneumatogen at a critical temperature characteristic of the pneumatogen source.

[ 0070 ] The terms "include,""includes,""comprises,""has,""may,""contain,""contains," and variants thereof, as used herein, are intended to be open-ended transitional expressions, terms, or words that do not exclude the possibility of additional acts or structures. The singular forms "a,""and," and "the" include references to multiple entities unless the context clearly dictates otherwise. The present invention also contemplates other embodiments, "including,""consistingof," and "consisting essentially of," embodiments or elements, whether or not expressly set forth herein.

[ 0071 ] As used herein, the term "optional" or "optionally" means that the event or circumstance described by it may, but does not necessarily, occur, and that the description includes instances in which the event or circumstance occurs and instances in which it does not.

[ 0072 ] As used herein, the term "about" modifies, for example, the amount of an ingredient in a composition, concentration, volume, process temperature, process time, yield, flow rate, pressure, and the like, and denotes ranges thereof, when used in describing embodiments of the invention, refers to a variation in a numerical amount that can be determined, for example, by routine measurement and processing techniques used to prepare the compounds, compositions, concentrates, or use the compositions; due to error due to carelessness in the performance of these techniques; due to differences in the manufacture, source, or purity of starting materials or ingredients used to perform the methods, and the like immediate circumstances. The term "about" also includes amounts that differ due to aging of the composition from a particular initial concentration or mixture, and amounts that differ due to mixing or processing of the composition from a particular initial concentration or mixture. When modified by the term "about," the appended claims include equivalents of such amounts. Furthermore, where "about" is used to describe a range of values, such as "from about 1 to 5," the enumeration means "from 1 to 5" and "from about 1 to about 5" and "from 1 to about 5" and "from about 1 to 5" unless specifically limited by context.

[ 0073 ] As used herein, the term "essentially" means "consisting essentially of" as that term is understood in U.S. patent law, and includes "consisting of" as that term is understood in U.S. patent law. For example, a composition that is "substantially free" of a particular compound or material may not include that compound or material, or may have a small amount of that compound or material present, such as an unavoidable impurity, a product of a side reaction, or the result of incomplete purification. A "small amount" may be a trace, an immeasurable amount, an amount that does not interfere with a value or characteristic, or some other amount as indicated by the context. A composition that has "essentially only" the recited list of components may consist only of those components, or have a trace amount of some other component present, or have one or more additional components that do not materially affect the properties of the composition. Furthermore, "substantially" modifies, for example, the type or amount of an ingredient in a composition, property, measurable amount, method, value, or range used in describing embodiments of the invention, referring to a variation that does not affect the overall stated composition, property, amount, method, value, or range thereof in a way that nullifies the intended composition, property, amount, method, value, or range. Where modified by the term "substantially," the claims of the appended claims include equivalents within the meaning of this definition.

[ 0074 ] As used herein, any recited ranges of values are intended to include all values within the range, and should not be construed as support for claims listing any subranges having endpoints that actually represent numerical values within the recited range. By way of hypothetical illustrative example, the invention in this description of the range 1 to 5 should be considered as support for claims with respect to any of the following ranges: 1-5; 1-4; 1-3; 1-2; 2-5; 2-4; 3-5; 3-4; and 4-5.

[ 0075 ] In the embodiments disclosed herein, a method for extruding molten polymer foam includes, consists essentially of, or consists of adding a thermoplastic polymer and a source of pneumatogen to an inlet located at a first end of an extruder; heating and mixing the thermoplastic polymer and the source of pneumatogen in the extruder to form a molten pneumatic mixture, wherein the temperature of the molten pneumatic mixture exceeds a critical temperature of the source of pneumatogen; accumulating a quantity of molten pneumatic mixture in a region of a barrel of the extruder located near a second end of the extruder; creating a volumetric expansion in the barrel region, resulting in a pressure drop in the barrel region; allowing a period of time to elapse after the pressure drop; and dispensing molten polymer foam from the extruder.

[ 0076 ] In embodiments, the extruder is any machine designed and adapted for melting, mixing and dosing thermoplastic polymers and mixtures thereof, optionally with one or more materials such as fillers, nucleating agents, diluents, stabilizers, clarifiers, and the like; and, in addition, the extruder includes a collecting zone for accumulating a mass of mixed molten material, and, in addition, is capable of producing a volumetric expansion in the collecting zone, which is associated with a drop in pressure. Extruders are well known in the industry and are widely used for melting, mixing and processing molten thermoplastic polymers. In embodiments, the extruder is adapted and designed to melt, mix and dosing a mixture of a thermoplastic polymer and a source of pneumatogen. Such extruders are designed to produce molten pneumatic mixtures at a pressure sufficient to prevent or substantially prevent the formation of pneumatogen voids in the molten pneumatic mixture.

[ 0077 ] In embodiments, extruders applicable for performing these methods include an internal volume, referred to in the technology as the "drum" of the extruder, intended and adapted to receive a solid thermoplastic polymer, and also to perform melting and mixing thereof. In embodiments, the extruder defines an internal volume designed to receive a solid thermoplastic polymer and a pneumatogen or a source of a pneumatogen, and also to perform melting of at least the polymer, and to mix the pneumatogen or a source of a pneumatogen with the molten polymer, to obtain a molten pneumatic mixture. In embodiments, the extruder additionally includes a collection zone for accumulating a mass of the molten pneumatic mixture material. In embodiments, the extruder additionally includes a device for creating a volumetric expansion in the collection zone, which is associated with a pressure drop.

[ 0078 ] In embodiments, the extruder is an injection molding machine. In embodiments, the extruder is a SODICK ^™ molding machine sold by Plustech Inc. of Schaumburg, Illinois. In embodiments, the extruder includes either one or two elements known in the art as "screws" housed within an internal volume known in the art as a "barrel." In embodiments, the screws have a regular round cylindrical shape along their entire length and further include one or more projecting screw elements called "wings." In some embodiments, the extruder is a single-screw extruder, defined as including a single screw housed movably within the barrel for rotating the barrel about its axis, for lateral movement of the barrel along its axis, or a combined movement including both rotation and lateral displacement. In other embodiments, the extruder is a twin-screw extruder, defined as comprising two screws positioned movably within a barrel in a substantially parallel and intimate relationship with one another, wherein each screw is positioned movably within the barrel to rotate the barrel about its axis, to move the barrel laterally along its axis, or to perform a combined movement comprising both rotation and lateral displacement. Furthermore, the screws of a twin-screw extruder are positioned such that the action of the screws, when they rotate in opposite directions, determines the desired mixing and propelling mode of the molten thermoplastic polymer located within the barrel.

[ 0079 ] In embodiments, the extruder is further adapted and designed to receive a solid thermoplastic polymer. In embodiments, the barrel of the extruder is further adapted and designed to introduce a solid thermoplastic polymer by having an inlet port located near the first end of the extruder and designed to add the solid thermoplastic polymer to the barrel. The solid thermoplastic polymer is added to the inlet port in any suitable form, such as grains, granules, powder, ribbons, tiles, all of which are forms familiar to those skilled in the art. In embodiments, the extruder includes a second, third, or even a fourth, or more, inlet ports adapted and designed to add or introduce one or more additional materials, including one or more solid materials, liquids or gases, into the internal volume of the extruder, for further mixing the one or more additional materials with the thermoplastic polymer. The internal volume of the extruder is adapted to receive, contain and melt the thermoplastic polymer and, optionally, one or more additional materials; and subjecting a thermoplastic polymer and optionally one or more additional materials to heat, shear, and mixing to form a molten mixture, while simultaneously advancing the molten mixture in a direction typically extending from its first end to its second end. In embodiments where the extruder is a single-screw extruder or a twin-screw extruder, the shearing, mixing, and advancing are accomplished by rotating the screw or two counter-rotating screws.

[ 0080 ] In embodiments of the extruder, the internal volume or a portion thereof is surrounded or partially surrounded by one or more heat sources. Heat sources suitably configured to heat the internal volume of the extruder include, in various embodiments, heating water jackets, heating oil jackets, electrical resistive heaters, open or shielded flame sources, or another heat source. The heat source operates to increase the temperature in the internal volume of the extruder. The temperature is suitably selected by the operator to melt the thermoplastic polymer and/or maintain a desired temperature within a portion of the internal volume of the extruder. In embodiments, the extruder is formed to include more than one heat source, wherein the heat sources operate independently to provide a skilled person with the ability to create a number of temperature "zones" throughout the internal volume. Additional temperature zones in some extruders may be provided in connection with the addition of one or more materials to their inlet ports, or to remove one of the many materials from their outlet ports. In embodiments, temperatures within one or more temperature zones are adjusted by the operator to provide greater control and optimization of melting, mixing, shearing, and advancement of the thermoplastic polymer and, optionally, one or more additional materials.

[ 0081 ] The extruder is generally designed and adapted to apply and maintain pressure in its internal volume during heating, mixing and moving the molten mixture. In embodiments, the extruder is adapted and designed to apply and maintain a first pressure in the internal volume or drum during heating, mixing and moving the molten mixture. In embodiments, the pressure inside the drum during heating, mixing and moving the molten pneumatic mixture is sufficient to prevent or substantially prevent leakage of the molten pneumatic mixture from the drum. In embodiments, the pressure inside the drum is sufficient to prevent the formation of air cavities in the molten pneumatic mixture when the temperature inside the drum exceeds the critical temperature of the pneumatogen source. In embodiments, the pressure inside the drum is substantially sufficient to prevent the formation of air cavities in the molten pneumatic mixture when the temperature inside the drum exceeds the critical temperature of the pneumatogen source. In such embodiments described in this paragraph, the term "substantially" includes accidental leakage of material or accidental pressure drop in the barrel due to manufacturing conditions, aging, or operating conditions of the extruder and/or screw, as known to a skilled person. Furthermore, in such embodiments, "substantially" in the context of "sufficient to prevent the formation of voids in the molten pneumatic mixture" means that a small percentage, such as up to 10% of the pneumatogen, may inadvertently form voids when pressure is maintained in the molten pneumatic mixture; however, the operator's goal is to maintain sufficient pressure to prevent the formation of voids.

[ 0082 ] In embodiments, the extruder barrel includes a collection zone for accumulating a mass of molten mixture in preparation for dispensing the molten mixture from the extruder. This mass of molten mixture is selected by the user. In embodiments, the molten mixture is molten pneumatic mixture. In such embodiments, the term used in the art to describe the accumulation of the mass of molten pneumatic mixture in the collection zone of the extruder barrel is called "injection accumulation." As will be understood by one skilled in the art of injection molding technology, to accumulate the injected material, the mass of molten pneumatic mixture is collected by advancing the molten pneumatic mixture from a first end toward the second end of the extruder - that is, toward and in the collection zone - by rotation of the screw or screws (or another mixing element), and thereby allowing the accumulation of molten pneumatic mixture in the collection zone until all of the desired mass of molten pneumatic mixture is collected and placed in the collection zone of the barrel. The collection area is located between the screw or screws and the second end of the extruder, and is in pressure communication with the rest of the barrel.

[ 0083 ] In conventional injection molding for producing thermoplastic polymer foams, a mass of molten pneumatic compound, or "injection material," is collected or "accumulated" in a collection zone by propelling the molten pneumatic compound toward and into the collection zone by rotation of a screw or screws (or another mixing element). The injection material is said to be accumulated when the entire selected mass of molten pneumatic compound is located within the collection zone. One skilled in the art will understand that the above description of melt mixing devices, such as the mechanical elements and features of an extruder or other melt mixing device, and further the above description of the methods for producing and accumulating molten pneumatic compounds in the injected material, correspond to conventional devices and methods for using such devices for producing molten pneumatic compounds and accumulating them for injection.

[ 0084 ] According to these known methods and devices, the injected molten pneumatic mixture material is conventionally prevented or substantially prevented from forming air voids while it is in the barrel, including during mixing, heating, advancing, and accumulation, and further while placed within a collection zone. Typically, when a desired amount of injected material has accumulated in the collection zone, a valve or door located between the collection zone and an outlet channel located at the second end of the extruder is opened, creating fluid communication from the barrel with the outlet channel for metering the injected material from the extruder. In some embodiments, when the valve or door is opened, a mechanical plunger pushes the molten pneumatic mixture out of the barrel and through the outlet channel. In embodiments, the screw or screws are suitably used in a lateral advance towards the second end of the extruder, which in turn pushes the molten pneumatic mixture out of the collecting area of the barrel and through the discharge channel.

[ 0085 ] The inventors of the present invention have found that, after accumulation of the injected material of the molten pneumatic mixture in the collection zone of the extruder, it is useful to form, create or determine a volumetric expansion in the collection zone of the extruder, wherein the creation thereof is accompanied by a drop in pressure in the collection zone; to allow a period of time to elapse after the creation, referred to herein as an expansion period; and to meter the injected material from the extruder after the expansion period. The injected material in such embodiments is metered in the form of a molten polymer foam. In embodiments, the volumetric expansion is created near the injected material located inside the collection zone of the extruder. In embodiments, the injected material is not mixed or subjected to an applied shear load or tension when the volumetric expansion is in the process of developing. In embodiments, the injected material is not advanced during the expansion period. In embodiments, the injected material is left in a stationary state, or holding, undisturbed or substantially undisturbed in the collection zone during the expansion period. In any of the above embodiments, the injected material may be heated during the expansion period; however, in some embodiments, heat is not supplied to the injected material during the expansion period.

[ 0086 ] After the expiration or completion of the expansion period, the molten polymer foam may be discharged from the second end of the extruder. The molten polymer foam includes a plurality of air voids. Without intending to be bound by theory, the inventors believe that the air voids are formed when the molten pneumatic mixture is subjected to volumetric expansion and an accompanying pressure drop (second pressure). In accordance with known physical principles, the formation of air voids is likely due to the creation of volumetric expansion and an accompanying pressure drop in the collection area of the drum, together with the expansion period in which the air voids are formed by the action of the pneumatogen. In some embodiments, the creation of volumetric expansion after accumulation of the injected material results in superior properties inherent in the molten polymer foam that is dosed. In other words, the inventors of the present invention have found that forming a molten pneumatic mixture under pressure, followed by a reduction in pressure and the concomitant formation of a certain volume before dispensing the mixture (such as into a mold cavity), results in the formation of a molten polymer foam, which, upon cooling, creates a product from a hardened polymer foam having unexpected and very favorable physical properties.

[ 0087 ] The inventors of the present invention have discovered that molten polymer foams discharged from an extruder according to the above-described methods provide significant technical advantages. These advantages are manifested in cured polymer foams, which are formed by cooling the molten polymer foam to a temperature below the transition temperature of the thermoplastic polymer in the molten state. The structure of articles obtained using molten polymer foam dosed from the extruder after a period of expansion differs both macroscopically and microscopically from polymer foams obtained by standard methods; and exhibits excellent properties suitable, for example, for structural elements. Articles made of polymer foam formed using the methods, devices and materials described herein are characterized by having a continuous thermoplastic matrix throughout their length, and a plurality of air cavities distributed throughout the polymer foam article. This characteristic is valid for products with thicknesses exceeding 2 cm, volumes exceeding 1,000 ^cm3 , or thicknesses exceeding 2 cm in addition to volumes exceeding 1,000 ^cm3 , between 1,000 ^cm3 and 5,000 ^cm3 , or even more than 5,000 ^cm3 ; and, in addition, for products with a volume exceeding 1,000 ^cm3 and a thickness exceeding 2 cm, a volume between 1,000 ^cm3 and 5,000 ^cm3 and a thickness exceeding 2 cm, or a volume exceeding 5,000 ^cm3 and a thickness exceeding 2 cm.

[ 0088 ] In embodiments, creating a volumetric expansion in a single-screw extruder is suitably achieved by lateral advancement of the screw toward the first end of the extruder and displacement from the collection zone of the extruder where the injected material accumulates. In embodiments, creating a volumetric expansion in a twin-screw extruder is achieved by lateral displacement of both screws toward the first end of the extruder and displacement from the collection zone of the extruder where the injected material accumulates. The lateral displacement is not necessarily accompanied by rotation of the screw or screws. That is, one or two screws can rotate during the lateral displacement, or the rotation can be stopped during the lateral displacement. It will be understood that creating a volumetric expansion by lateral displacement of one or two screws is favorably selected by the extruder operator to obtain the selected volumetric expansion. That is, the distance of lateral displacement of the screw or screws to create a volumetric expansion is suitably selected by the operator.

[ 0089 ] Accordingly, in embodiments, the volumetric expansion is specified by the operator to add sufficient volume to the collection zone to accommodate the entire anticipated volume of molten polymer foam; or some percentage thereof. The total anticipated volume of molten polymer foam of the injected material may be calculated based on the amount of thermoplastic polymer and the pneumatogen source plus any additional materials added to accumulate the injected material, with the assumption that the entire pneumatogen source will participate in forming pneumatogen voids in the resulting molten polymer foam. Those skilled in the art will understand that commercially available pneumatogen sources are supplied with information suitable for calculating the total anticipated volume of molten polymer foam based on the amount of pneumatogen source added to form the injected material and other process conditions. In embodiments, the volumetric expansion is the difference between the volume of injected material and the expected volume of molten polymer foam. In embodiments, the volumetric expansion is set to achieve between 10% and 100% of the total expected volume of the molten polymer foam, such as between 15% and 100%, or between 20% and 100%, or between 25% and 100%, or between 30% and 100%, or between 35% and 100%, or between 40% and 100%, or between 45% and 100%, or between 50% and 100%, or between 55% and 100%, or between 60% and 100%, or between 65% and 100%, or between 70% and 100%, or between 75% and 100%, or between 80% and 100%, or between 85% and 100%, or between 90% and 100%, or between 10% and 95%, or between 10% and 90%, or between 10% and 85%, or between 10% and 80%, or between 10% and 75%, or between 10% and 70%, or between 10% and 65%, or between 10% and 60%, or between 10% and 55%, or between 10% and 50%, or between 10% and 45%, or between 10% and 40%, or between 10% and 35%, or between 10% and 30%, or between 10% and 25%, or between 10% and 20%, or between 10% and 15%, or between 15% and 20%, or between 20% and 25%, or between 25% and 30%, or between 30% and 35%, or between 35% and 40%, or between 40% and 45%, or between 45% and 50%, or between 50% and 55%, or between 55% and 60%, or between 60% and 65%, or between 65% and 70%, or between 70% and 75%, or between 75% and 80%, or between 80% and 85%, or between 85% and 90%, or between 90% and 95%, or between 95% and 100% of the difference between the volume of material injected and the expected volume of molten polymer foam. In still other embodiments, the volumetric expansion is a value between 100% and 300% of the difference between the volume of the injected material and the expected volume of the molten polymer foam, such as from 100% to 105%, or from 100% to 110%, or from 100% to 115%, or from 100% to 120%, or from 105% to 110%, or from 110% to 115%, or from 115% to 120%, or from 120% to 125%, or from 120% to 150%, or from 150% to 200%, or from 200% to 250%, or from 250% to 300% of the difference between the volume of the injected material and the expected volume of the molten polymer foam.

[ 0090 ] After volume expansion is created, a period of time is allowed to pass or lapse before metering the molten polymer foam from the extruder. In embodiments, the period of time is referred to as the expansion period. In some embodiments, no mixing, moving, shearing, other physical actions, or other additional volume changes are performed within the collection zone during the expansion period. Instead, in such embodiments, the injected material is allowed to remain within the collection zone for the duration of the expansion period. At the end of the expansion period, the molten polymer foam is withdrawn from the outlet channel of the extruder. In embodiments, the molten polymer foam is metered into a mold cavity, and the molten polymer foam is cooled to a temperature below the transition temperature of the thermoplastic polymer to the molten state to produce an article made of cured polymer foam.

[ 0091 ] In embodiments, the expansion period is selected by the operator to be between about 5 seconds and 600 seconds, depending on the sample mass, the source and amount of pneumatogen, and any additional materials in the injected material. In embodiments, the expansion period is from 5 seconds to 600 seconds, or from 5 seconds to 500 seconds, or from 5 seconds to 400 seconds, or from 5 seconds to 300 seconds, or from 20 seconds to 600 seconds, or from 20 seconds to 500 seconds, or from 20 seconds to 400 seconds, or from 20 seconds to 300 seconds, or from 10 seconds to 200 seconds, or from 20 seconds to 200 seconds, or from 30 seconds to 200 seconds, or from 40 seconds to 200 seconds, or from 50 seconds to 200 seconds, or from 5 seconds to 190 seconds, or from 5 seconds to 180 seconds, or from 5 seconds to 170 seconds, or from 5 seconds to 160 seconds, or from 5 seconds to 150 seconds, or from 5 seconds to 140 seconds, or from 5 seconds to 130 seconds, or from 5 seconds to 120 seconds, or from 5 seconds to 110 seconds, or from 5 seconds to 100 seconds, or from 5 seconds to 90 seconds, or from 5 seconds to 80 seconds, or from 5 seconds to 70 seconds, or from 5 seconds to 60 seconds, or from 5 seconds to 50 seconds, or from 5 seconds to 40 seconds, or from 5 seconds to 30 seconds, or from 5 seconds to 20 seconds, or from 5 seconds to 10 seconds, or from 10 seconds to 15 seconds, or from 15 seconds to 20 seconds, or from 20 seconds to 25 seconds, or from 25 seconds to 30 seconds, or from 30 seconds to 35 seconds, or from 35 seconds to 40 seconds, or from 40 seconds to 45 seconds, or from 45 seconds to 50 seconds, or from 50 seconds to 55 seconds, or from 55 seconds to 60 seconds, or from 60 seconds to 70 seconds, or from 70 seconds to 80 seconds, or from 80 seconds to 90 seconds, or from 90 seconds to 100 seconds, or from 100 seconds to 110 seconds, or from 110 seconds to 120 seconds, or from 120 seconds to 130 seconds, or from 130 seconds to 140 seconds, or from 140 seconds to 150 seconds, or from 150 seconds to 160 seconds, or from 160 seconds to 170 seconds, or from 170 seconds to 180 seconds, or from 180 seconds to 190 seconds, or from 190 seconds to 200 seconds, or from 200 seconds to 250 seconds, from 250 seconds to 300 seconds, or from 300 seconds to 350 seconds, or from 350 seconds to 400 seconds, or from 400 seconds to 450 seconds, or from 450 seconds to 500 seconds, or from 500 seconds to 550 seconds, or from 550 seconds to 600 seconds.

[ 0092 ] The use of the above methods results in the formation of a molten polymer foam that obtains certain significant technical advantages, described in the sections below, when the molten polymer foam is cooled to a temperature below the molten transition temperature of the thermoplastic polymer to form a cured polymer foam. Polymer foam articles are generally characterized as monolithic articles having a continuous polymer matrix that forms a plurality of air cavities distributed throughout the volume of the article. In embodiments, polymer foam articles are particularly characterized as having a continuous polymer matrix that forms a plurality of air cavities distributed in a surface region, wherein the surface region is defined as the region of the article between the surface of the article (the polymer foam-air interface) and at a distance of 500 microns (μm) inward from the surface.

[ 0093 ] An exemplary embodiment of a device effectively used to perform the above methods is shown in FIG. 1A. FIG. 1A is a schematic illustration of an exemplary single-screw injection molding device 20 in accordance with the embodiments disclosed herein, which is suitable for performing the methods described herein for producing molten polymeric foams and polymeric foam articles also disclosed herein. As shown in FIG. 1A, the injection molding system 20 includes a barrel 21 connected to a motor or drive section 24 and to a mold section 26. The barrel 21 includes a first end 21a, a second end 21b, and defines a hollow inner barrel section 22. The barrel section 22 further defines a nozzle 36 near the second end 21b of the barrel. The screw 30 is located within the inner barrel section 22 and includes a screw end portion 34. The screw 30 is operatively connected to the motor section 24 for rotating the screw 30 about its central axis; or for lateral displacement, indicated by the arrow Z. The lateral displacement of the screw 30 can occur in the direction from the first end 21a of the drum towards the second end 21b of the drum; or in the direction from the second end 21b of the drum towards the first end 21a of the drum. The lateral displacement of the screw 30 in any direction is not necessarily associated with a rotational movement. The screw 30 further includes one or more wings 31, which are mixing elements for mixing and moving materials present inside the drum section 22, mainly from the first end 21a of the drum towards the second end 21b of the drum. The screw 30 is placed inside the section 22 of the drum in a pressure-tight relationship with it, for creating pressures exceeding the atmospheric pressure, maintained inside the section 22 of the drum, by the wings 31 of the screw inside the drum 21 and, in addition, by the state of the check valve 32. The shut-off valve 37 is connected to the drum near the second end 20b, and acts to regulate the communication by fluid medium, the connection under pressure, or both, between the nozzle 36 and the section 26 of the mold. The check valve 32 is placed inside the section 22 of the drum and surrounds the screw 30 to prevent back pressure, which would induce the materials located in the section 22 of the drum to move towards the first end 21a of the drum, and thereby creates a pressure-tight, sealed by a flowing material, or sealed by a flowing material under pressure relationship between the shut-off valve 37 and the check valve 32.

[ 0094 ] Furthermore, with respect to FIG. 1A, the mold section 26 includes two mold sections 38, as shown. The mold sections 38 are removably connected to each other, defining a cavity 39. In some embodiments, one or more of the mold sections 38 are movable, allowing for the removal of an article made of cured polymer foam therefrom. In some embodiments, the mold sections 38 are in a pressed position against each other; in other embodiments, the mold sections 38 are separated from each other by a gap.

[ 0095 ] In embodiments, the methods disclosed herein are suitably performed using an apparatus such as the system 20 shown in FIGS. 1A-1B. In FIG. 1A, a selected mass of mixture 42A including a selected amount of a thermoplastic polymer, a pneumatogen source, and optionally one or more additional materials is added to a drum section 22 through an inlet 28, as shown by arrow A. In some embodiments, the pneumatogen source is a pneumatogen, the inlet 28 or another inlet (not shown) is a gas inlet in pressure communication with the drum section 22; and the pneumatogen is added into the gas inlet channel at a selected pressure, while non-gaseous materials are introduced through the inlet channel 28. During the addition of the mixture 42A into the section 22 of the drum through the inlet channel 28, the motor 24 operates to rotate the screw 30. The rotation of the screw 30 advances and mixes the mixture 42A to the end 34 of the screw. A heat source (not shown) is suitably used to supply heat to the mixture 42A inside the section 22 of the drum. The motor 24 rotates the screw 30 to advance the mixture 42A located in the section 22 of the drum in a direction generally extending from the first end 21a of the drum 21 towards the second end 21b until it reaches the end 34 of the screw. In addition, the rotation of the screw 30 provides for mixing of the mixture 42A during advancement. When the mixture 42A is advanced and mixed as a result of rotation of the screw 30, heating elements or band heaters (not shown) near the drum section 22 act to heat the mixture 42A. A plurality of heating zones may be located near the drum section 22 to vary the temperature inside the drum section 22 between the first end 21a and the second end 21b of the drum 21. During advancement, the screw 30 rotating inside the drum section 22 acts to mix the mixture 42A; and heat is supplied to the mixture as it advances, thereby raising the temperature of the mixture above the melting temperature of the thermoplastic polymer to transform the mixture 42A into a molten pneumatic mixture, at least upon reaching the second end 21b of the drum 21. In addition, the position of the screw 30 inside the drum section 22, in which the wings 31 are in contact with the drum 21 during rotation of the screw 30; in combination with the check valve 32, the shut-off valve 37 in the closed position, or both of them, creates a pressure-tight relationship within the drum section 22, as a result of which the molten pneumatic mixture 42B is in the drum section 22 at a pressure exceeding atmospheric pressure. The pressure within the drum section 22 is sufficient to prevent or substantially prevent the formation of air pockets, even if the pneumatogen source is heated above its critical temperature.

[ 0096 ] Furthermore, the rotation of the screw 30 creates a movement of the compressed molten pneumatic mixture toward the end 34 of the screw, moving or accumulating a selected mass of the compressed molten pneumatic mixture 42B within the collection section 40 of the drum section 22. The collection section 40 is defined as an area within the volume of the drum section 22 extended between the check valve 32 and the shut-off valve 37 in FIG. 1A, in addition, as an area of the drum section 22 extended along the distance X of the drum 21. The selected mass, or "injection material", of the compressed molten pneumatic mixture 42B is collected, or accumulated, in the collection section 40 of the drum section 22. The pressure within the collection section 40 is sufficient to prevent or substantially prevent the formation of air voids in the molten pneumatic mixture. In embodiments, the injected material substantially fills the collecting section 40.

[ 0097 ] The accumulation of the injectable material of the molten pneumatic mixture 42B is achieved using standard methods familiar to those skilled in the art. Conventional and known variations of the methods and materials used to accumulate the injectable material are encompassed by the methods described herein. Once the injectable material has been accumulated, it can be processed by the methods disclosed herein to obtain all of the technical advantages disclosed herein with respect to the formation of polymeric foams and polymeric foam articles. For example, methods such as the MUCELL® high-pressure process from Trexel Inc., Wilmington, Massachusetts, which adds a pneumatogen source in the form of a gas directly to the extruder under pressure mixing to prevent or substantially prevent the formation of air voids and subsequent accumulation of the injectable material, are suitably used to form the injectable material. Various patent documents and trade publications further describe specialized embodiments of melt mixing and propelling for producing molten pneumatic mixtures and forming an injectable material, such as specialized screw designs for mixing and counter-current characteristics, and the like; any of which can be effectively used in connection with the above-mentioned methods and apparatuses for forming an injectable material, for producing an injectable material as described herein, and accumulating the injectable material under pressure within a collecting zone of the melt mixing apparatus.

[ 0098 ] Once the injected material is formed and accumulated in the collection zone, a volumetric expansion is created therein, and the expansion is further accompanied by a decrease in pressure in the collection zone and close to the injected material. Accordingly, FIG. 1A shows an apparatus 20 for a molten pneumatic mixture in which a screw 30 is arranged to collect the injected material in a collection zone 40. The injected material includes a selected mass of molten pneumatic mixture 42B and is under pressure within the collection zone 40. At this stage of the method, in addition to FIG. 1A, FIG. 1B shows an apparatus 20 in which a screw 30 is arranged to create a volumetric expansion 44 within the collection zone 40. In some more detail, FIG. 1B shows the screw 30 in a position obtained by lateral displacement of the screw 30 toward the first end 21a of the drum; that is, the screw 30 in FIG. 1B is retracted relative to FIG. 1A. The retraction and the achieved partial displacement of the screw 30 from the collecting zone 40 determines the volumetric expansion 44 inside the collecting zone 40 and additionally causes a decrease in pressure inside the collecting zone 40. In some embodiments, the rotation of the screw 30 is stopped before retraction. In some embodiments, the rotation of the screw 30 is stopped during retraction or after completion of retraction. The retraction distance of the screw 30, that is, the distance of lateral displacement of the screw 30 toward the first end 21a of the drum, is selected by the operator to create the appropriate volumetric expansion 44.

[ 0099 ] In some embodiments shown in FIG. 1B, the volume expansion 44 is selected by the operator to create a collection zone 40 having a total volume that corresponds to the expected volume of molten polymer foam from the injected material; in such embodiments, the total volume in the collection zone 40 after the addition of the volume expansion 44 is the total expected volume of molten polymer foam of the molten pneumatic mixture 42B in FIG. 1B. In other embodiments, the volume expansion 44 is selected by the operator to create a collection zone 40 having a total volume that corresponds to a percentage of the expected volume of molten polymer foam from the injected material, or of the injected material located in the collection zone 40; that is, the total volume in the collection zone 40 after the addition of the volume expansion 44 is equal to a value of from about 50% to 120% of the total expected volume of molten polymer foam. In some embodiments, volumetric expansion is set to create a total volume in the collection zone to accommodate 100% of the total expected volume of molten polymer foam. The total expected volume of molten polymer foam injected can be calculated based on the amount of thermoplastic polymer and the pneumatogen source, plus any additional materials added to accumulate the injected material, assuming that the entire pneumatogen source will contribute to the formation of air voids in the resulting molten polymer foam.

[ 00100 ] After the screw 30 is retracted to create a volumetric expansion 44, as shown in FIG. 1B, a period of time called the "expansion period" is allowed to elapse or pass, while the injected material is held inside the collection zone 40, as shown in FIG. 1B, more specifically, wherein the collection zone 40 includes the volumetric expansion 44. The expansion period is selected by the operator to be between 5 seconds and 200 seconds. In embodiments, during the expansion period, the injected material is left to stand undisturbed or substantially undisturbed inside the collection zone 40. In embodiments, "undisturbed" means that the injected material is not subjected to any influences that cause mixing, shearing or movement (flow) of the injected material during the expansion period. In embodiments, "substantially undisturbed" means that the quiescent state of the injected material is not intentionally subjected to influences that lead to mixing, shearing or movement during the expansion period, but, for example, temperature differences, leakage and other process problems may lead to accidental stress or deformation of the injected material located in the collection zone during the expansion period.

[ 00101 ] After the expansion period, the nozzle shut-off valve 37 is opened, as shown in FIG. 1B, and the molten polymer foam is metered from the drum 22. In embodiments, as shown in FIGS. 1A-1B, the molten polymer foam flows into the cavity 39. The metering may be by means of a pressurized discharge using a mechanical device, such as displacement using the lateral displacement of a screw, or by supplying compressed gas to the collection area, but in some embodiments, the application of pressure is not necessary for metering the molten polymer foam. In embodiments, the pressure at the nozzle 36, as shown in FIG. 1A-1B, during the discharge of molten polymer foam is from 1 psi to 20 psi above gravity, such as from 3 psi to 20 psi, from 5 psi to 20 psi, from 7 psi to 20 psi, from 10 psi to 20 psi, from 15 psi to 20 psi, from 1 psi to 15 psi, from 1 psi to 10 psi, from 1 psi to 7 psi, from 1 psi to 5 psi, from 2 psi to 5 psi, from 5 psi to 10 psi, from 10 psi to 15 psi, or from 15 psi to 20 psi, without adding external pressure sources, such as extruding molten polymer foam using additional lateral displacement of screw 30 towards the second end 21b of the drum in FIGS. 1A-1B. In embodiments, dosing is performed while maintaining fluid communication between nozzle 36 and cavity 39. In some such embodiments, the fluid communication additionally comprises a pressure communication.

[ 00102 ] Immediately after placement within the cavity 39 formed by the mold portions 38 shown in FIGS. 1A-1B, the molten polymer foam is cooled until it reaches a temperature below the melt transition temperature of the thermoplastic polymer, such as under ambient conditions. In some embodiments where volumetric expansion is configured to create a total volume in the collection zone that is less than 100% of the total intended volume of the molten polymer foam, air voids may continue to nucleate and/or develop (increase in size) after the molten polymer foam has been dispensed and before the temperature has been reduced sufficiently to reach the melt transition temperature of the thermoplastic polymer. Cooling of the molten polymer foam is carried out using traditional methods for cooling injection molded products, and includes immersing the mold in a liquid coolant having a predetermined temperature, or spraying the mold with a liquid coolant, such as liquid water; blowing an air stream onto the mold; cooling in ambient air; and the like, without limitation.

[ 00103 ] In an alternative embodiment of the above methods, the device 20 configured as shown in FIG. 1B is used to form the molten polymer foam. FIG. 1B shows the screw 30 in a position achieved by lateral displacement of the screw 30 toward the first end 21a of the drum; that is, the screw 30 in FIG. 1B is retracted compared to FIG. 1A. The retraction and the resulting partial displacement of the screw 30 from the collection zone 40 determines a volumetric expansion 44 inside the collection zone 40 and further causes a pressure drop inside the collection zone 40. The device 20 configured as shown in FIG. 1B is used to mix, heat and propel the molten pneumatic mixture 42B toward the second end 21b of the drum 21 in substantially the same way as described above. In addition, the position of the screw 30 inside the section 22 of the drum, while its wings 31 are in contact with the drum 21 during the rotation of the screw 30; in combination with the check valve 32, the shut-off valve 37 in the closed position, or both of them, creates a hermetically sealed pressure relationship inside the section 22 of the drum, as a result of which the molten pneumatic mixture 42B is in the section 22 of the drum under a pressure exceeding the atmospheric pressure. The pressure inside the section 22 of the drum is sufficient to prevent or substantially prevent the formation of pneumatic cavities, even if the source of the pneumatogen is heated above its critical temperature. However, in this alternative embodiment, the molten pneumatic mixture moves through the check valve 32 and into the collecting section 40, further increased by the volumetric expansion 44.

[ 00104 ] An advantage of the now disclosed methods is that conventional materials and devices for extrusion and injection molding are suitable for performing the methods. No specialized requirements for equipment and materials are needed for performing the disclosed methods. Thus, any thermoplastic material or mixture thereof that is suitable for injection molding and/or for forming polymer foams can be effectively combined with any industrially used pneumatogen source using conventional technology, such as a standard injection molding device, optionally together with one or more additional materials selected by the operator of the device.

[ 00105 ] In embodiments, thermoplastic polymers useful in connection with the methods, devices, and articles described herein include any thermoplastic materials or mixtures thereof that are known in the industry as useful for injection molding or injection molding of polymer foam articles; and mixtures of such polymers. Useful polymers are characterized by having a melt flow viscosity suitable for use in injection molding, such as injection molding. As such, the thermoplastic polymers may have a degree of crosslinking that is thermoreversible or that otherwise does not prevent sufficient melt flow viscosity for injection molding processes.

[ 00106 ] In embodiments, thermoplastic polymers useful in connection with the methods, devices, and articles described herein include olefin polymers such as polyethylene, polypropylene, poly-α-olefins, and various copolymers and branched/crosslinked versions thereof, including, but not limited to, low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), thermoplastic polyolefin elastomer (TPE), ultra high molecular weight polyethylene (UHMWPE), and the like; polyamides (PA), polyimides (PI), polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyhydroxyalkanoates (PHAs) such as polyhydroxybutyrate (PHB), polycarbonates (PC), polylactic acids (PLA), acrylonitrile-butadiene-styrene copolymers (ABS), polystyrenes, polyurethanes including thermoplastic polyurethane elastomers (PU, TPU), polycaprolactones, polyvinyl chlorides (PVC), tetrafluoroethylene copolymers, polyether sulfones (PES), polyacetals, polyaramids, polyphenylene oxides (PPO), polybutylenes, polybutadienes, polyacrylates and methacrylates (derivatives of acrylic acids), ionomeric polymers (SURLYN® and similar olefin copolymers with ionic functional groups), ethers polyether-amide block copolymers (PEBAX®), polyaryletherketones (PAEK), polysulfones, polyphenylene sulfides (PPS), polyamide-imide copolymers, polybutylene succinates, cellulosic materials, polysaccharides, and their copolymers, alloys, compounds and blends useful in connection with the methods described herein, without limitation.

[ 00107 ] With respect to the unlimited use of polymer compounds and blends, the inventors of the present invention have found that mixed plastic waste streams for recycling are applicable in embodiments as thermoplastic polymers. Thus, in embodiments, ocean plastic waste is a mixed plastic waste stream caught from the oceans and collected on the shores and has an approximate content of 10%-90% polyolefins, a content of 10%-90% PET, a content of 1%-25% polystyrene, and a content of 1% to 50% unknown polymer. Such mixed plastic streams and plastic waste streams, not limited to those collected from the oceans and from the shores, are similarly suitable for forming molten polymer foams and polymer foam articles using the methods and devices described herein.

[ 00108 ] Sources of pneumatogens are commonly available in the industry, and conditions suitable for introducing pneumatogens during melt mixing are well known and described in detail. Accordingly, any source of pneumatogen useful for injection molding, reaction injection molding, or other methods for producing polymeric foams is useful herein for forming molten polymeric foams and cured polymeric foam articles in accordance with the methods, apparatuses, and polymeric foam articles described herein. Pneumatogens useful in connection with the methods and apparatuses described herein include air, _CO2 , and _N2 , either as encapsulated within a thermoplastic material in the form of beads, granules, and the like, or in a latent form that chemically reacts to release _CO2 or _N2 when heated within a melt mixing device. Such chemical reactions are typically exothermic or endothermic, without limitation with respect to their use in connection with the methods and apparatuses described herein. Suitable sources of pneumatogens include sodium bicarbonate, polycarboxylic acid compounds such as citric acid, or a salt or ester thereof, such as sodium citrate or sodium citrate trimethyl ester; mixtures of sodium bicarbonate with a polycarboxylic acid, such as citric acid; sulfonyl hydrazides, including para -toluenesulfonyl hydrazide (p-TSH) and 4,4'-oxybis-(benzenesulfonyl hydrazide) (OBSH), pure and modified azodicarbonamides, semicarbazides, tetrazoles, and diazinones. In any of the above, the pneumatogen source is optionally further encapsulated in a polymeric carrier designed to melt during heating, mixing, and accumulation of the injected material.

[ 00109 ] In embodiments, useful pneumatogen sources include commercially available compositions such as HYDROCEROL® BIH 70, HYDROCEROL® BIH CF-40-T, or HYDROCEROL® XH-901, all manufactured by Clariant AG, Switzerland; FCX 7301, manufactured by RTP Company, Winona, Minnesota; FCX 27314, manufactured by RTP Company, Winona, Minnesota; CELOGEN® 780, manufactured by CelChem LLC, Naples, Florida; ACTAFOAM® 780, manufactured by Galata Chemicals, Southbury, Connecticut; ACTAFOAM® AZ, manufactured by Galata Chemicals, Southbury, Connecticut; ORGATER MB.BA.20, manufactured by ADEKA Polymer Additives Europe, Mulhouse, France; ENDEX 1750 ^™ , manufactured by Endex International, Rockford, Illinois; and FOAMAZOL ^™ 57, manufactured by Bergen International, East Rutherford, New Jersey.

[ 00110 ] In some embodiments, the pneumatogen source is a pneumatogen, and the pneumatogen is fed as a gas to a melt mixing device, such as an extruder similar to that shown in FIGS. 1A-1B. In such embodiments, the gas is allowed to dissolve in the thermoplastic polymer by direct addition under pressure and mixing within the melt mixing device. In some embodiments, the gas becomes a supercritical fluid upon compression, either before dissolving or simultaneously with dissolving in the molten thermoplastic polymer. Injecting the pneumatogen directly into the injection molding device is referred to in the industry as the MUCELL® process, practiced by Trexel Inc., Wilmington, Del. This technology requires specialized equipment, such as a controlled pressurized fluid connection (a reservoir, cylinder, etc.) to the extruder inlet to create a pressure connection with the barrel, where the thermoplastic polymer is also added to the barrel and melted. Where such specialized equipment is available, a pneumatogen is typically used as the pneumatogen source, in conjunction with the methods described herein for directly incorporating the pneumatogen into the thermoplastic polymer and one or more additional materials to form a molten pneumatic mixture.

[ 00111 ] A pneumatogen source is added to the thermoplastic polymer, and any optional one or more additional materials, in an amount that provides a selected reduction in the density of the thermoplastic polymer, in accordance with standard technology related to the desired density of the polymer foam and the action of pneumatogens and pneumatogen sources to form thermoplastic polymer foams. The amount of the pneumatogen source added to the thermoplastic polymer is not particularly limited; accordingly, the inventors of the present invention have found that up to 85% of the density reduction is achieved without the use of polymer or glass hollow beads or the like, to create a polymer foam article having the unique and unexpected characteristics described below and, in addition, exhibiting the desired density reduction of up to 85%. As used herein, "density reduction" means the percentage reduction in mass in a polymeric foam article compared to the same article without the addition of a pneumatogen (source) to produce the article (i.e., the polymeric article excluding or substantially excluding air voids). Thus, in embodiments, the molten polymer foams and polymer foam articles advantageously do not contain glass or polymer hollow beads, while providing a selected density reduction of up to 85%, for example, from 30% to 85%, such as from 35% to 85%, from 40% to 85%, from 45% to 85%, from 50% to 85%, from 55% to 85%, from 60% to 85%, from 65% to 85%, from 70% to 85%, from 75% to 85%, from 30% to 35%, from 35% to 40%, from 40% to 50%, from 50% to 55%, from 55% to 60%, from 60% to 65%, from 65% to 70%, from 70% to 75%, from 75% to 80%, or from 80% to 85%. The introduction of glass or polymer hollow beads provides a further extension of the achievable density reduction of a polymer foam article made in accordance with the methods described herein. In some embodiments, more than 85% density reduction can be achieved. However, polymer foam articles that have the advantage of density reduction are characterized as having a continuous polymer matrix throughout the volume with air cavities distributed therein, including molded articles having a volume of more than 1000 cm ³ , from 1000 cm ³ to 5000 cm ³ , or even over 5000 cm ³ ; and moulded articles with a volume exceeding 1000 ^cm3 and a thickness exceeding 2 cm, with a volume between 1000 ^cm3 and 5000 ^cm3 and a thickness exceeding 2 cm, or with a volume exceeding 5000 ^cm3 and a thickness exceeding 2 cm.

[ 00112 ] As mentioned above, the amount of the pneumatogen source added to the thermoplastic polymer is not particularly limited; accordingly, the inventors of the present invention have found that up to 70% of the total volume of the polymer foam article includes air voids. The volume of air voids as a percentage of the total volume of the polymer foam article is called the "void ratio" of the article; thus, a void ratio (porosity) of up to about 70% is achieved without including polymer or glass hollow beads or the like, to obtain a polymer foam article having the unique and unexpected characteristics described below and, in addition, having a desired porosity of up to 70% of the volume of the polymer foam article. Thus, in embodiments, the molten polymer foams and polymer foam articles described herein advantageously do not contain glass or polymer hollow beads, while providing a void ratio of up to 70%, such as 5% to 70%, such as 10% to 70%, 15% to 70%, 20% to 70%, 25% to 70%, 30% to 70%, 35% to 70%, 40% to 70%, 45% to 70%, 50% to 70%, 55% to 70%, 60% to 70%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%, 25% to 30%, from 30% to 35%, from 35% to 40%, from 40% to 50%, from 50% to 55%, from 55% to 60%, from 60% to 65%, or from 65% to 70%. The introduction of glass or polymer hollow beads provides for further expansion of the achievable porosity of the polymer foam article made in accordance with the methods described herein. In some embodiments, more than 70% porosity can be achieved. However, polymer foam articles having 70% porosity are characterized as having a continuous polymer matrix throughout its volume with air cavities distributed therein, including molded articles having a volume greater than 5000 cm ³ , a thickness greater than 2 cm, or both a volume greater than 5000 cm ³ and a thickness greater than 2 cm.

[ 00113 ] In some embodiments, the thermoplastic polymer and the pneumatogen source are mixed before the mixture is introduced into the melt mixing device for heating and mixing. In other embodiments, the thermoplastic polymer and the pneumatogen source are added separately to the melt mixing device, such as through two separate inlet channels or ports provided for introducing materials into the melt mixing device. In still other embodiments, the solid mixture, including both the thermoplastic polymer and the pneumatogen source, is added through a single inlet channel of the melt mixing device for heating and mixing.

[ 00114 ] In embodiments, one or more additional materials are introduced or added to the melt mixing device along with the thermoplastic polymer and the pneumatogen source; such additional materials are typically mixed or blended with the thermoplastic polymer and the pneumatogen source, or both; or one or more additional materials are added to the melt mixing device separately, such as through an individual port or inlet. Examples of suitable additional materials include colorants (dyes and pigments), stabilizers, clarifiers, nucleating agents, fibers, particulate materials, and fillers. Specific examples of some suitable materials include talc, titanium dioxide, glass hollow spheres or beads, thermoplastic polymer particles, fibers, beads, or hollow spheres, and thermosetting polymer particles, fibers, beads, or hollow spheres. Further examples of suitable materials include fibers such as glass fibers, carbon fibers, cellulose fibers, and fiber-containing cellulose, natural fibers such as cotton or wool fibers, and synthetic fibers such as polyester, polyamide, or aramid fibers; and include microfibers, nanofibers, crimped fibers, chopped or sliced fibers, mixed phase-separated fibers such as bicomponent fibers including any of the above polymers, and thermosetting materials formed from any of the above polymers. Further examples of suitable additional materials are waste materials, suitably chopped or sliced, and including textile or non-woven materials, rags, or paper; sand, gravel, crushed stone, slag, recycled concrete, and geosynthetic aggregates; and other biological, organic, and mineral wastes and mixed streams thereof. Additional examples of suitable additive materials include minerals such as calcium carbonate and dolomite, clays such as montmorillonite, sepiolite, and bentonite, micas, wollastonite, mixtures of hydromagnesite and huntite, synthetic minerals, silica agglomerates or colloids, aluminum hydroxide, aluminosilicate composite colloids and dispersions, halloysite nanotubes, magnesium hydroxide, basic magnesium carbonate, precipitated calcium carbonate, and antimony oxide. Additional examples of suitable additive materials include carbon-containing fillers such as graphite, graphene, graphene quantum dots, carbon nanotubes, and C ₆₀ -fullerenes. Additional examples of suitable additive materials include thermally conductive fillers such as boron nitride (BN) and surface-treated BN.

[ 00115 ] In embodiments, one or more additional materials are introduced or added to the melt mixing device together with the thermoplastic material and the pneumatogen source in an amount of from about 0.1% to 50% by weight of the thermoplastic polymer, such as from 0.1% to 45%, from 0.1% to 40%, from 0.1% to 35%, from 0.1% to 30%, from 0.1% to 25%, from 0.1% to 20%, from 0.1% to 15%, from 0.1% to 10%, from 0.1% to 9%, from 0.1% to 8%, from 0.1% to 7%, from 0.1% to 6%, from 0.1% to 5%, from 0.1% to 4%, from 0.1% to 3%, from 0.1% to 2%, from 0.1% to 1%, from 1% to 50%, from 2% to 50%, from 3% to 50%, from 4% to 50%, from 5% to 50%, from 6% to 50%, from 7% to 50%, from 8% to 50%, from 9% to 50%, from 10% to 50%, from 11% to 50%, from 12% to 50%, from 13% to 50%, from 14% to 50%, from 15% to 50%, from 20% to 50%, from 25% to 50%, from 30% to 50%, from 35% to 50%, from 40% to 50%, from 45% to 50%, from 0.1% to 2%, 2% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%, 25% to 30%, 30% to 35%, 35% to 40%, 40% to 45%, or 45% to 50% by weight of the thermoplastic polymer added to the melt mixing devices to form the injection material.

[ 00116 ] Accordingly, with respect to melt mixing devices that are not extruders, it will be understood by one skilled in the art that the following methods will result in a molten polymer foam having significant technical advantages as described in the sections below. A method of forming and collecting molten polymer foam comprises the following: heating and mixing a thermoplastic polymer and a pneumatogen source to form a molten pneumatic mixture, wherein the temperature of the molten pneumatic mixture exceeds a critical temperature of the pneumatogen source and a pressure applied to the molten pneumatic mixture is sufficient to substantially prevent the formation of pneumatogen voids; accumulating a selected amount of the molten pneumatic mixture in a collection area; creating a volumetric expansion in the collection area near the molten pneumatic mixture that causes a pressure drop; maintaining the volumetric expansion during the expansion period; and collecting the molten polymer foam from the collection area. In embodiments, the molten pneumatic mixture remains undisturbed or substantially undisturbed during the expansion period.

[ 00117 ] In some embodiments, collecting molten polymer foam includes introducing molten polymer foam into a cavity formed by a mold; and cooling the molten polymer foam below the melting temperature of the thermoplastic polymer to form an article made of polymer foam. In embodiments where molten polymer foam is introduced into the mold cavity, the cooled polymer foam takes on the shape and dimensions of the mold, and then the polymer foam is characterized as a continuous polymer matrix having air cavities distributed throughout the volume of the article. In embodiments, molten polymer foam is introduced into the mold cavity with the ability of the molten polymer foam to flow and enter the mold cavity under the action of gravity; in some such embodiments, the flow is unimpeded and ensures filling of the open cavity. In other embodiments, molten polymer foam is introduced in a pressurized flow mode into the molding element. In embodiments, molten polymer foam is fed into the mold cavity in fluid communication with it through a nozzle or other device for feeding molten polymer foam from the collection zone of the melt mixing device.

[ 00118 ] For example, in embodiments, the extruder is adapted and designed to dispense molten mixture from an outlet port into a forming element, which is a mold that forms a cavity therein and is designed and adapted to receive the molten polymer mixture, such as a molten pneumatic mixture. In embodiments, the forming element is a mold configured and adapted to receive the molten thermoplastic polymer discharged from the outlet port, and, in addition, the mold is typically characterized as forming a recess or cavity having a selected shape and dimensions of the desired article.

[ 00119 ] In embodiments, dispensing from the extruder is accomplished by mechanical pumping, by applying pressure of gaseous material from within the extruder barrel, or by a combination thereof. In other embodiments, after the expansion period has elapsed, an outlet channel, valve, damper, nozzle, or door in the collection area is simply opened, and the molten polymer foam is allowed to flow unimpeded through the outlet channel; the melt stream is then directed to fill the molding element. In other embodiments, the molding element is in fluid communication with the outlet channel, and is further designed and adapted to be filled with the molten mixture so that the molten mixture takes on a selected shape when it cools and solidifies. In some embodiments, the molding element is in fluid communication with the outlet channel of the extruder so that pressure is maintained between the collection area, the outlet channel, and the molding element or mold. Any conventional thermoplastic molding or casting process involving injection molding of polymeric articles, such as polymeric foam articles, properly utilizes the molding of the molten polymeric foams described herein.

[ 00120 ] In embodiments where molten polymer foam is allowed to flow freely through an outlet port, or is forced under pressure from an outlet port without additional flow resistance, the melt flow eventually encounters a surface, such as a surface generally perpendicular to the direction of melt flow. The inventors of the present invention have observed that the flow in such circumstances then takes on a generally cylindrical (spiraling) and planar (folded) shape during continuous melt flow, such as reported by Batty and Bridson, "Accurate Viscous Free Surfaces for Buckling, Coiling, and Rotating Liquids," Symposium on Computer Animation, Dublin, July 2008. In embodiments, molten polymer foam is allowed to flow, or "spill," freely from the outlet port of a melt mixing device and enter a mold that is formed as an open container. In some embodiments, the open container mold is completely filled with molten polymer foam; in other embodiments, the open container mold is partially filled with molten polymer foam.

[ 00121 ] In some embodiments relating to the above-described spiral melt flow, the melt flow is substantially shear-free, or is a substantially linear melt flow, or is a melt flow that is substantially linear and shear-free, creating fluid communication between the outlet of the extruder and the interior of the mold cavity. In some such embodiments, the melt flow may acquire a spiral melt flow pattern either as a result of impinging on a perpendicular surface or by flowing down a substantially vertical wall or side of the mold cavity and collecting at the bottom of the mold cavity. A schematic representation of one such embodiment is shown in FIG. 41, which shows an embodiment of the extruder of FIGS. 1A-1B, in which the mold 26 of the device 20 is on a substantially horizontal surface 100. In reference to elements as shown in FIG. 1A-1B, there is no shut-off valve 37 at the distal end 21b of the drum 21; instead, in FIG. 41, the collecting zone 40 extends to the mold valve 137 located near the mold cavity 39. Thus, the mold valve 137 acts as forming the collecting zone 40, or to create a discharge channel for dosing the molten polymer foam into the mold cavity 39 in the form of a substantially linear horizontal flow 110. The mold valve 137 is at a height H above the horizontal surface 100, and at a height H2 above the floor or bottom 120 of the mold 26, as located on the horizontal surface 100. With reference to FIG. 41, the mold valve 137 is selectively opened to create a fluid communication between the collecting zone 40 and the mold cavity 39. Thus, the mold valve 137 is selectively opened to create a substantially linear horizontal flow 110 of molten polymer foam entering the mold cavity 39. Upon entering the mold cavity 39, the linear flow flows downward at a distance H2, and in some embodiments, takes on a spiral melt flow shape when the mold cavity 39 is filled. Other related embodiments of methods and devices are considered with respect to the creation of a swirling melt flow, as described herein.

[ 00122 ] In embodiments, when a polymer foam article is cooled and removed from an open container or mold positioned as shown in FIG. 41, a swirling and wrinkled flow pattern is visible on the surface of the article. One example of such a visible flow pattern can be seen, for example, in FIGS. 2-2 and 2-4. When the interior of polymer foam articles formed using swirling and wrinkled flow is cryogenically crushed and examined under a microscope, the interior of the article is free or substantially free of flow patterns, interfaces, or other evidence of swirling and wrinkled flow. For example, cryogenic crushing of such polymer foam articles does not result in cracking at any discernible interface between swirls and folds; and both macroscopic and microscopic examination of the interior of such polymer foam articles yields a uniform appearance with respect to the flow pattern. The physical properties of such polymer foam articles are consistent with the physical properties obtained by subjecting molten polymer foam to a directed flow of liquid under conditions of fluid communication between the outlet channel of the melt mixing device and the mold, or by subjecting molten polymer foam to a directed flow of liquid under pressure.

[ 00123 ] In some embodiments, the methods herein include essentially filling a mold with molten polymer foam formed in accordance with the above-described methods, then cooling the molten polymer foam to form a cured polymer foam; and, further, in embodiments, removing an article of the cured polymer foam from the mold. In embodiments, cooling is cooling to a temperature below the transition temperature of the thermoplastic polymer in the molten state. In embodiments, cooling is cooling to a temperature in equilibrium with the ambient temperature. In some embodiments, the mold further includes one or more vents to equalize pressure in the mold during its filling with molten polymer foam, but in other embodiments, vents are not present. After cooling, the article of the polymer foam can be removed from the mold for further modification or use.

[ 00124 ] In accordance with any of the above descriptions, Table 1 presents useful, but non-limiting, examples of processing conditions used to produce molten polymer foam using a standard single-screw extruder of the reaction injection molding type, further using one or more representative thermoplastic polymers and a citric acid-based pneumatogen source, as indicated.

[ 00125 ] Table 1. Representative thermoplastic polymers and conditions,

applicable for the production and formation of molten polymer foams.

Variables Polymer samples High-impact polystyrene PET PC/ABS Polyamide 6/15% talc Thermoplastic elastomer Surlyn ionomer 30% LDPE
/70% PP PMMA Foaming agent, %
Hydrocerol BIH 70 (endothermic) or
Hydrocerol XH-901 (exothermic) 2 (endo) 3 (endo) 3 (endo) 2 (endo) 2 (endo) 2 (endo) 2 (endo) 3% (endo)
+0.5% (exothermic) Mold Cavity Size (inches) 4×4×2 4×4×2 4×4×2 6-inch sphere 4×4×2 4×4×2 3-inch sphere 4×4×2 Volume of injected material (cm ³ ) 545 545 545 1856 545 545 252 545 Injection volume (cm ³ ) 4026.3 4294.7 295.0 983.2 327.7 278.6 98.3 180.3 Decompression volume (cm ³ ) 131.1 409.7 1065.2 819.4 163.9 49.2 49.2 163.9 Melting point (ºС) 213 227 221 265 221 150 360 226 Mold closing force (tons) 10 10 15 20 10 17 14 10 Cooling time (sec) 120 120 90 160 320 500 120 160 Decompression time (sec) 60 80 60 100 60 50 56 100 Holding pressure (MPa) 0 0 0 0 0 0 0 0 Holding time (sec) 0 0 0 0 0 0 0 0 Injection speed ( ^cm3 /sec) 0.066 0.098 0.041 0.066 0.057 0.066 0.082 0.049 Mold temperature (ºС) 10 43 29 44 30 10 20 35 Auger rotation speed (m/sec) 0.15 0.11 0.21 0.15 0.15 0.15 0.12 0.09 Specific back pressure (MPa) 6.90 12.41 7.59 10.34 8.97 8.97 6.90 5.17 Injection pressure (MPa) 31.03 37.93 41.38 34.48 48.28 129.66 13.79 14.48 Density of the finished part (g/cm ³ ) 0.456 0.571 0.597 0.454 0.594 0.476 0.327 0.482

[ 00126 ] In embodiments, mold sizes that are effectively used to form polymer foam articles produced using the methods and materials disclosed herein include molds that define cavities that can be filled with a single injection of molten polymer foam, or a series of cavities that can be filled with a single injection of molten polymer foam. The mold cavity size itself is limited only by the amount of injected material that can be accumulated in the melt mixing device used by the user. Exemplary mold cavities having volumes of up to 1×10 ⁵ cm ³ are useful for producing large parts such as automotive cabin or exterior parts, I-beam structural parts, and other large plastic parts that effectively utilize polymer foam. Furthermore, the shape of the mold cavities is not particularly limited and may be complex in terms of overall outlines and with flat surface profiles and features, such as shapes recognizable as dumbbells, cutlery, decorative globes with protruding geographic elements, shapes in the form of people, animals, or insects, the shape of a frame or case for framing or packaging, for example, electronic products, devices, automobiles, and the like, shapes for the subsequent placement and fitting of screws, bolts and other non-thermoplastic objects in or through an article made of polymer foam; and the like are all suitable profiles of molds for molding an article made of polymer foam, as described herein. In some embodiments, the cavity includes a thickness gradient of up to 300% from one or more regions of the cavity.

[ 00127 ] In accordance with any of the above descriptions, Table 2 provides useful, but non-limiting, examples of mold cavity volumes and sizes for molding molten polymer foams, either by flowing under pressure or by free flowing molten polymer foam into the mold. In addition, larger mold volumes, such as up to 100,000 ^cm3 or more, are applicable where the mass of material injected is suitably increased.

[ 00128 ] Table 2. Representative volumes and dimensions of mold cavities applicable for molding molten polymer foams.

Detail Cavity volume (cm ³ ) Sphere with a diameter of 3 inches 231.00 Sphere with a diameter of 6 inches 1856.66 Sphere with a diameter of 9 inches 6243.47 Sphere with a diameter of 18 inches 50038.52 Pin body 4771.10 Pin head 812.80 12×12×1 slab (in inches) 2359.74 Bar 4×4×2 (in inches) 545.69 4x4x4 block (in inches) 1091.38 Block 12×12×12 (inches) 28316.84 Plate 17×4×1 (in inches) 1114.32 11x4x2 slab (in inches) 1442.06 Plate 2×2×0.5 (inches) 32.77 2x2x2 block (in inches) 131.10 Plate 2.625×5.625×1 (inches) 241.97 Plate 1x1x2 (in inches) 32.77

[ 00129 ] Any of the methods, processes, applications, machines, devices, or individual features thereof described above may be freely combined with one another to form polymer foams and polymer foam articles having unique and unexpected characteristics. Thus, in embodiments, the polymer foam article is formed using the methods, materials, and devices described above. The polymer foam article is a separate monolithic object obtained by molding or casting molten polymer foam in accordance with any of the methods and materials disclosed above, as well as variations thereof, which may be combined in any part and in any way to form molten polymer foam, as described above.

[ 00130 ] Accordingly, the terminology used to refer to methods, materials, and devices in the above discussion is used below to refer to articles made using one or more of the methods, materials, and devices described in the above discussion.

[ 00131 ] In embodiments, any combination of the above methods results in the formation of an article from a polymer foam, which comprises, consists essentially of, or consists of a continuous matrix of a thermoplastic polymer, forming a plurality of air cavities. The continuous matrix of a thermoplastic polymer comprises, consists of, or consists essentially of a solid thermoplastic material, that is, the thermoplastic polymer is present at a temperature below the transition temperature to the molten state. In embodiments, the continuous matrix of a thermoplastic polymer, furthermore, includes one or more additional materials dispersed in the solid thermoplastic polymer.

[ 00132 ] Polymer foam articles have reduced densities, based on the density of the thermoplastic polymer and any other materials added to form the polymer foam, by a selected number of percent, based on the amount of the pneumatogen source added to the injected material. In embodiments, the density reduction is 30%, 40%, 50%, 60%, 70%, and even up to 80% reduced density, as selected by the user. In embodiments, a density reduction of up to 85% is achieved solely due to the presence of air cavities continuously distributed in the polymer matrix. In embodiments, the polymer foam articles do not contain hollow dispersed particles, such as polymer or glass hollow beads, added to the injected material before molding the polymer foam article using the methods and devices described herein.

[ 00133 ] Furthermore, in connection with the reduced density as mentioned above, the polymeric foam articles herein are characterized as having a continuous thermoplastic polymer matrix throughout, or substantially throughout, their entire length. The inventors of the present invention have found that large polymeric foam articles can be effectively formed from the molten polymeric foams described herein by including a continuous polymer matrix containing a plurality of air voids. "Large" articles are those having volumes of 1000 ^cm3 or more, such as ^{2000 cm3} or more, 3000 cm3 or more, 4000 ^cm3 or more, or 5000 ^cm3 or more, or any volumes between 1000 ^cm3 and 5000 ^cm3 ; and including volumes of up to 10,000 ^cm3 , up to 20,000 ^cm3 , up to 50,000 ^cm3 , or even up to 100,000 ^cm3 or more. Thus, large polymer foam articles can be effectively molded by incorporating a continuous polymer matrix containing multiple air cavities throughout its entire length. The article volume is limited only by the mold cavity size and the amount of injected material that can accumulate in the melt mixing device. In embodiments, a large article is molded with a single injection, dosed from a single outlet channel of the melt mixing device, that is, without dividing the flow of molten polymer foam into multiple simultaneous distribution pipes, nozzles, or other methods of directing multiple streams simultaneously into a single mold cavity.

[ 00134 ] Furthermore, the inventors of the present invention have found that thick polymer foam articles can be effectively formed by including a continuous polymer matrix containing a plurality of air voids. Thickness, as referred to herein, means the straight-line distance through the interior of the polymer foam article between any two points on its surface. "Thick" articles are defined as having a thickness of 2 cm or more, such as 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 45 cm, or even 50 cm or more. In some embodiments, a polymer foam article formed using the methods and materials described herein is characterized as large and thick. Furthermore, the large, thick polymer foam article is characterized as having a continuous polymer matrix containing multiple air voids throughout the article. In these embodiments, the large, thick article is formed with a single injection, dosed from a single outlet port of a melt mixing device, i.e., without dividing the molten polymer foam flow into multiple simultaneous distribution pipes, nozzles, or other methods of directing multiple streams simultaneously into a single mold cavity.

[ 00135 ] The manufacture of large, thick, or large and thick polymer foam articles is challenging in industry due to the cooling gradient of the molten foam after it is dispensed into a cavity of such dimensions. The interior of such articles tends to cool very slowly, and some of the thermoplastic polymer in the mold cavity may remain above its melting temperature, causing significant fusion of the air voids before the thermoplastic material cures (reaches a temperature below its molten transition state). In sharp contrast, the inventors of the present invention have found that large articles, thick articles, and large, thick articles are properly formed using the methods, materials, and apparatuses disclosed herein, wherein the molded polymer foam article is further characterized by a continuous polymer matrix having air voids distributed throughout the article. Slow cooling of the large articles exhibits minimal or no evidence of fusion of the air voids during cooling. The air voids remain intact or substantially intact during cooling of the molten polymer foam and do not coalesce during cooling, resulting in a continuous polymer matrix regardless of the size, thickness, or volume of the formed polymer foam article.

[ 00136 ] This feature of the polymer foam articles described herein is unexpected and unpredictable: the methods according to the prior art result in foams that are prone to merging of the air cavities during cooling. Accordingly, molten polymer foam according to the traditional technology, located in the interior volume of the mold, can cool so slowly that the air cavities are capable of completely merging, and, consequently, the interior of a large or thick article formed using standard polymer foaming methods can receive very large openings or even a completely destroyed structure in their interior. In sharp contrast to this, molten polymer foams formed according to the present methods are not subject to significant merging or destruction of the continuous polymer matrix during cooling of the molten polymer foam. Accordingly, large and thick polymer foam articles with a continuous polymer matrix throughout their entire length are achieved using the methods, materials and devices described herein.

[ 00137 ] The continuous polymer matrix as a structural feature of polymer foam articles according to the above methods, devices and materials is characterized as being present throughout the polymer foam article, including in the surface region thereof. The surface region may accordingly be characterized as an internal region of the polymer foam article that is 500 microns (μm) or less from the surface. The surface region, as defined herein, is a portion of the region of the foam article commonly referred to as the "skin layer", which is an area that does not contain air voids or is substantially free of air voids in a polymer foam article produced using standard methods. Conventionally formed polymer foam articles include a skin layer that is at least as thick as the surface region, i.e., 500 microns (μm) thick; but often the skin layer is much thicker and can extend as far as 1 mm, 1.5 mm, 2 mm, 2.5 mm, even 3 mm from the surface of the article. However, polymer foam articles produced using the methods now disclosed possess a true foam structure from their surface and throughout their entire thickness and volume. In embodiments, microscopic examination has shown evidence of the presence of air voids on the surface of polymer foam articles formed using the conditions, methods, and materials disclosed herein. Accordingly, the methods disclosed herein yield unexpected results in terms of the continuous nature of the polymer matrix structure throughout the entire length of the polymer foam article, in any direction, and in any region within very large and/or thick polymer foam articles, as well as at the surface and in the surface region of the article.

[ 00138 ] The following Examples include analyses of the surface region of multiple polymer foam articles formed using the methods disclosed herein and which exhibit this continuous foam structure. When examined macroscopically, a polymer foam article formed using the methods disclosed herein may appear to have a dermal layer; that is, the surface region of the article may have a different appearance than the interior region of the article. However, the inventors of the present invention have found that, in sharp contrast to the dermal layer, which is characterized by the absence of air voids, the surface regions of polymer foam articles produced by the present methods include a plurality of compressed air voids. When examined macroscopically, the compressed air voids create an appearance resembling a dermal layer; however, macroscopic examination has shown that the visually apparent difference arises from the "flattened" or compressed state of the continuous polymer matrix near the surface of the article.

[ 00139 ] Thus, by way of example, as can be seen in FIG. 17 and FIG. 18, there is a gradual transition from spherical to compressed air cavities as one moves toward the surface of the polymer foam article formed using the conditions, methods, and materials disclosed herein. Thus, in embodiments, a surface region of the polymer foam article made using the methods disclosed herein includes a plurality of compressed air cavities. In embodiments, compressed air cavities are present in a surface region of the polymer foam article formed using the methods disclosed herein. In some such embodiments, compressed air cavities are present within an interior region of the polymer foam article that is located at a distance of 500 microns (μm) or less from the surface. In some such embodiments, compressed air cavities are present within an internal region of the polymer foam product that is 2 cm from the surface. Compressed air cavities are defined as air cavities having a circularity of less than 1, where a circularity value of zero represents a completely non-spherical air cavity, and a value of 1 represents a perfectly spherical air cavity. In embodiments, air cavities having a roundness of less than 0.9 are found in the surface area of polymer foam articles, and, in addition, from 10% to 90%, or from 10% to 80%, or from 10% to 70%, or from 10% to 60%, or from 10% to 50%, or from 10% to 40%, or from 10% to 30%, or from 10% to 20%, or from 20% to 80%, or from 20% to 70%, or from 20% to 60%, or from 20% to 50%, or from 20% to 40%, or from 20% to 30%, or from 30% to 70%, or from 30% to 60%, or from 30% to 50%, or from 30% to 40% of the air cavities in the surface region have a roundness of 0.9 or less. In embodiments, the average roundness in the surface region of the polymer foam articles is from 0.70 to 0.95, such as from 0.75 to 0.95, or from 0.80 to 0.95, or from 0.85 to 0.95, or from 0.90 to 0.95, or from 0.70 to 0.90, or from 0.70 to 0.85, or from 0.70 to 0.80, or from 0.70 to 0.75, or from 0.70 to 0.75, or from 0.75 to 0.80, or from 0.80 to 0.85, or from 0.85 to 0.90, or from 0.90 to 0.95.

[ 00140 ] In embodiments, compressed air cavities are present in the polymer foam article at a distance of more than 500 microns (µm) from its surface. For example, in embodiments, compressed air cavities are present at a distance of up to 1 mm from the surface of the polymer foam article, or up to 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 1 cm, or more, from its surface. In some embodiments, the area of compressed air cavities in the polymer foam product corresponds to a value from 0.01% to 70% of the total volume of the product, for example, from 0.1% to 70%, or from 0.5% to 70%, or from 1% to 70%, or from 2% to 70%, or from 3% to 70%, or from 4% to 70%, or from 5% to 70%, or from 6% to 70%, or from 7% to 70%, or from 8% to 70%, or from 9% to 70%, or from 10% to 70%, or from 15% to 70%, or from 20% to 70%, or from 30% to 70%, or from 40% to 70%, or from 50% to 70%, or from 60% to 70%, or from 0.01% to 60%, or from 0.01% to 60%, or from 0.01% to 50%, or from 0.01% to 40%, or from 0.01% to 30%, or from 0.01% to 20%, or from 0.01% to 10%, or from 0.01% to 9%, or from 0.01% to 8%, or from 0.01% to 7%, or from 0.01% to 6%, or from 0.01% to 5%, or from 0.01% to 4%, or from 0.01% to 3%, or from 0.01% to 2%, or from 0.01% to 1%, or from 0.01% to 0.1% of the total volume of the product.

[ 00141 ] FIGS. 12 and 14 show a curve of the average air void size and the average number of air voids versus the average circularity of the air voids for two polymer foam articles produced using the presently disclosed methods. Quantitative analysis of the size and distribution of air voids revealed an inverse relationship between the average air void size and the number of air voids.

[ 00142 ] FIG. 18 further shows visual confirmation that air voids are present at the surface of polymer foam articles produced using the methods, materials, and devices described herein. FIG. 18 further shows visual confirmation that a plurality of compressed air voids are present substantially 500 microns (μm) from the surface of polymer foam articles produced using the methods, materials, and devices described herein. In this sense, the now disclosed polymer foam articles are significantly different from the foam articles according to the prior art. While the "skin layer," or the first 500 microns (μm) of the thickness of the foam article produced by standard methods, does not include air voids or is substantially free of them, a feature of the foam articles according to the prior art is primarily that the air voids are spherical wherever they are located. Thus, within the thickness of a standard foamed product, where air voids are observed, they are typically spherical, with a circularity close to 1 or similar. Compressed air voids are not formed when using traditional foam manufacturing methods, and therefore, no circularity distribution of air voids is observed in such standard foamed products. Furthermore, air voids do not even form within the first 500 microns (µm) of the foamed product thickness produced by the standard method, so a comparison cannot be made between the air voids in the surface region of polymer foam products, as described here, and foamed products formed by traditional injection molding methods.

[ 00143 ] Furthermore, the conditions, methods, and materials disclosed herein are suitably optimized to form polymeric foam articles having different physical properties depending on the intended end use or application. For example, the density of the polymeric foam article is suitably varied as a function of volumetric expansion. By reducing volumetric expansion, the density of the resulting polymeric foam article can be reduced in a substantially linear relationship, such as shown in FIG. 5. It can also be seen in FIG. 5 that increasing the time of the expansion period causes the formation of a denser polymeric foam article. Such conditions and other variables, all of which are within the limits of the conditions, methods, and materials disclosed herein, are effectively used to vary the physical properties of the resulting polymeric foam articles.

[ 00144 ] In one variation of the conditions, methods, and materials disclosed herein, molten polymer foam is properly metered by dividing the flow of molten polymer foam into 2, 3, 4, or more ducts directed into a plurality of molds or mold sections to form a plurality of polymer foam articles from a single injected material. In another variation of the conditions, methods, and materials disclosed herein, two injected materials are used to fill a single mold, wherein the first injected material differs from the second injected material in terms of thermoplastic polymer content or blended polymer ratio, pneumatogen source, one or more optionally included additional materials, density, porosity, depth of compressed void area, or some other difference with respect to material or physical property.

[ 00145 ] In yet another variation of the conditions, methods, and materials disclosed herein, a polymeric foam article formed using the methods disclosed herein is subjected to an accelerated pull-out test in accordance with ASTM D6117. The polymeric foam articles exhibit superior pull-out resistance compared to foam articles formed using traditional foaming methods. Furthermore, the polymeric foam articles formed using the conditions, methods, and materials disclosed herein do not require pre-drilling, puncturing, or trimming to expedite placement.

[ 00146 ] In yet another variation of the conditions, methods, and materials disclosed herein, a polymeric foam article formed using the methods disclosed herein is ballistic tested. Using the National Institute of Justice (NIJ) standard "Ballistic Resistance of Body Armor NIJ Standard-0101.06," a series of 3-inch (7.62 mm) thick polymeric foam articles were formed from polyether-polyamide block copolymers (PEBAX®), linear low-density polyethylene (LLDPE), and polypropylene, using a citric acid-based pneumatogen source. Polymer foam articles formed using all three of these thermoplastic polymers were found to stop LR ("long rifle") small caliber ("long rifle") pistol bullets, thereby passing the NIJ Level I test; and were found to stop bullets from a 9mm LUGER® pistol, thus passing NIJ Levels II and IIA.

[ 00147 ] EXPERIMENTAL PART

[ 00148 ] The following examples are intended to further illustrate this invention and are not intended to limit the scope of the invention in any way. Examples 1 and 11 were made using an Engel Duo 550 Ton injection molding machine (manufactured by Engel Machinery Inc., York, PA, USA). Examples 2-4 were made using a Van Dorn 300 injection molding machine (manufactured by Van Dorn Demag, Strongsville, OH, USA). Unless otherwise stated, the remaining examples were made using an Engel Victory 340 Ton injection molding machine (manufactured by Engel Machinery Inc., York, PA, USA).

[ 00149 ] In the Examples given here, "cc" means "cubic centimeter" or "cubic centimeters" (cm ³ ), "sec" means "second" or "seconds".

Standard foam molding and MFIM

[ 00150 ] The Examples presented herein utilized two methods of injection molding expanded foam, referred to herein as “standard foam molding” and “molten foam injection molding” (“MFIM”).

[ 00151 ] In standard foam molding, the following general procedure was used: A) A mixture was formed by mixing a polymer (which may be in the form of grains, powder, beads, granules, etc.) with a foaming agent and any other additives such as filler. The mixture was introduced into an injection block, and the rotating screw of the injection block was driven, propelling the mixture forward in the barrel of the injection block, thereby forming a heated flowable material in accordance with normal injection molding techniques. B) A predetermined volume of material was accumulated in the front of the barrel of the injection block by rotating the screw, thereby propelling the predetermined volume from the feed zone to the front of the screw. During this feeding stage, the screw rotated to propel the molten mixture forward into the space in the barrel between the screw and the nozzle, thereby creating the predetermined volume. C) The molten mixture was injected into the mold cavity by forward movement of the screw and/or rotation of the screw.

[ 00152 ] The MFIM process employed the following general procedure: A) A mixture was formed by mixing a polymer (which may be in the form of plastic pellets, beads, powder, spheres, granules, and the like) with a chemical blowing agent and any other additives such as a filler. The mixture was introduced into an injection block, and the rotating screw of the injection block was driven, propelling the mixture forward in the barrel of the injection block, thereby forming a heated flowable material in accordance with normal injection molding techniques. B) A predetermined volume of material was accumulated in the front of the barrel of the injection block by rotating the screw, thereby propelling the predetermined volume from the feed zone to the front of the screw. During this feeding stage, the screw rotated to propel the molten mixture forward into the space in the barrel between the screw and the nozzle, thereby creating the predetermined volume. C) When the material had been advanced to the front of the screw, in a stage now called "decompression," the screw was drawn back from the nozzle without rotation or substantially without rotation to avoid advancing the material to the front of the screw.

[ 00153 ] A mixture-free space was created between the screw and the nozzle inside the barrel, wherein the specially created space is referred to herein as the "decompression volume". D) The material was maintained in the barrel between the screw and the nozzle for a period of time, referred to herein as the "decompression time". During the decompression time, the material foamed due to the pressure drop created by the space added in step (C). E) The molten foam was injected into the mold cavity by the forward advancement of the screw and/or rotation of the screw.

Example 1

[ 00154 ] Two parts were foam molded using a blend of low-density polyethylene mixed with 2% by weight of Hydrocerol® BIH 70 foaming agent (Clariant AG, Muttenz, Switzerland). Molding was performed using an Engel Duo 550 Ton injection molding machine (Engel Machinery Inc., York, Pennsylvania, USA). The mold cavity was approximately spherical in shape with a diameter of six inches (15.24 cm). The first part was molded using a standard foam molding process, and the second part was molded using the MFIM process. An aluminum mold with a cold runner and a runner system was used for both parts to feed a 6-inch diameter sphere into the cavity. The melt feed system was the same for each part, as were most of the process conditions. The process settings for the MFIM method and the standard foam molding method used as a control are detailed in TABLE 3. Parts with approximately equivalent mass were obtained from each processing run.

TABLE 3: Settings for Example 1; Equivalent Mass Study Standard foam molding method MFIM Drum temperature (ºС) 182/182/182/174/163/154/161/121/49 Mold temperature (ºС) 10 Injection speed ( ^cm3 /sec) 655.5 Back pressure (kPa) 17237 Decompression (cm ³ ) - 164 Auger rotation speed (cm/sec) 15.24 Cooling time (seconds) 160 Holding time (seconds) 30 - Holding pressure (kPa) 8963 - Weight of injected material (g) 328.9 331.9

[ 00155 ] The first and second parts were photographed. FIG. 2-1 is a photographic image of the first part molded using a standard foam molding method. As can be seen in the image, the standard foam molding method did not result in a part that filled the mold cavity, and the part did not conform to the shape of the spherical mold cavity.

[ 00156 ] FIG. 2-2 is a photographic image of a second part formed using the MFIM method. As can be seen in the image, the MFIM method resulted in a part that completely or substantially completely filled the spherical cavity of the mold, and the part matched or substantially matched the shape of the spherical cavity of the mold.

[ 00157 ] The first part, formed using the standard foam molding method, was cut into two pieces. FIGS. 2-3 and 2-5 are photographic images of one of the pieces of the part formed according to the standard foam molding method. As can be seen in the images, the first part contained a large hollow cavity.

[ 00158 ] The second part formed using the MFIM process was cut into two pieces. FIGS. 2-4 and 2-6 are photographic images of one of the pieces of the second part. As can be seen in the images, the second part did not have a large hollow cavity as in the part from the standard foaming process. The MFIM part had a cellular structure throughout its volume.

Example 2

[ 00159 ] Two parts were formed using foam injection molding, Part A using the standard foam molding method and Part B using the MFIM method. In both approaches, LDPE/talc pellets were dry-mixed with a foaming agent and stirred during loading into the molding machine.

[ 00160 ] For Part B, a mixture of low-density polyethylene (LDPE), talc, and Hydrocerol® BIH 70 was formed and fed into a Van Dorn 300 injection molding machine to form a polymer injection material inside the barrel. After the injection material accumulated in front of the screw, the screw was moved backward from the injection nozzle without rotation according to the MFIM method to create a space between the screw and the nozzle, where the space had a decompression volume. The mixture was then foamed in the space before injection into the mold.

[ 00161 ] The same procedure was performed for Part A, except that after the injection material had accumulated in front of the screw, the screw was not moved back from the nozzle, i.e., the decompression volume was zero. The injection material was metered to fill the mold under standard foam molding conditions to achieve a 10% weight reduction relative to a continuous part.

[ 00162 ] TABLES 4-7 below show the polymer, mold, setup, and process settings used in Example 2.

TABLE 4: Composition materials Weight % Polymer: LDPE 82% Filler: talc 15% Foaming agent: Hydrocerol® BIH 70 3%

TABLE 5: Basic molding parameters One-piece pan (2 x 4 x 4 inches) (5.08 x 10.16 x 10.16 cm) ASTM Mold Volume of the mold cavity (cm ³ ) 524.39 Sprue volume (cm ³ ) 17.39 Total volume (cm ³ ) 541.78

TABLE 6: General settings for producing a zero-decompression part and an MFIM part Drum temperature (ºС) 154|185|177|166 Mold temperature (ºС) 20 Back pressure (kPa) 0 Auger speed (rpm) 165 Auger rotation delay time (sec) 100 Holding time (sec) 10 Injection speed ( ^cm3 /sec) 394

TABLE 7: Independent settings Parameters of the injected material Detail A Detail B Polymer mass (g) 456.2 189.4 Volume of polymer in the drum (cm ³ ) 486.3 162.12 Decompression volume (cm ³ ) 0 231.57 Total amount of molten injected material (cm ³ ) 486,297 393.69 Cooling time (sec) 800 160

[ 00163 ] Each of Parts A and B was cut in half to reveal the cross-section. FIG. 3A and FIG. 3B show the resulting cross-sectional views of Part A and Part B, respectively. As shown in FIG. 3A, Part A had a thick outer region extending nearly 0.8 inches (20.3 mm) from the surface, indicating that more than 50% of the molded part was completely solid/continuous. The density of Part A was 0.84 g/cm ³ .

[ 00164 ] FIG. 3B shows a cross-section of Part B formed by the MFIM method using the settings given in TABLE 4 and TABLE 5. As can be seen from FIG. 3B, Part B had a foamed structure that included a distribution of cell sizes and shapes. The continuous, unfoamed outer region in Part B was almost absent. The density of Part B was 0.35 g/ ^cm3 .

[ 00165 ] A spherical cavity mold was used to mold additional parts, Part C and Part D, using foam injection molding. The same LDPE, talc, and Hydrocerol® BIH 70 blend composition was used to mold Parts C and D. Part C was molded using the MFIM process and Part D using a standard foam molding process. Both processes formed a spherical or approximately spherical part having a diameter of 6 inches (15.24 cm). Parts C and D were cut in half at the middle (widest portion) to expose the cross-section of the part. FIG. 4A is a photographic image of the cross-section of Part C formed using the MFIM process (471 g, required cooling time of 160 seconds). FIG. 4B is a photographic cross-sectional image of Part D produced by the standard foam molding process (1360 g, required cooling time 800 seconds).

[ 00166 ] Results similar to those obtained using a continuous mold were obtained. Part C, formed using the MFIM method, showed cells throughout the entire volume of the part, while Part D, formed using the standard foam molding method, showed a region near the outer surface of the part that was either free or substantially free of cells (“continuous”). Part C had a lower density than Part D.

Example 3

[ 00167 ] In Example 3, block parts were formed using the MFIM method at different decompression volumes (Test A), and different decompression volumes and decompression times (Test B).

[ 00168 ] TABLES 8-10 show information on the material composition, mold geometry, and process settings used for Tests A and B.

TABLE 8: Composition materials Weight % Polymer: LDPE 82% Filler: talc 15% Foaming agent: Hydrocerol® BIH 70 3%

TABLE 9: Basic molding parameters One-piece pan (2 x 4 x 4 inches) (5.08 x 10.16 x 10.16 cm) ASTM Mold Volume of the mold cavity (cm ³ ) 132.74 Sprue volume (cm ³ ) 17.39 Total volume (cm ³ ) 150.13

[ 00169 ] LDPE/talc composite pellets were mixed with a foaming agent immediately prior to molding.

[ 00170 ] Test A

[ 00171 ] In Test A, all variables were held constant except for the volume ratio of polymer to decompression volume (void space) in the barrel prior to injection. The settings for each specimen in Test A are shown in TABLE 10:

TABLE 10: Settings for Test A Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Drum temperature (ºС) 171|185|
177|166 171|185|
177|166 171|185|
177|166 171|185|
177|166 171|185|
177|166 Mold temperature (ºС) 21 21 21 21 21 Injection pressure (kPa) 4137 4137 4137 4137 4137 Back pressure (psi) 0 0 0 0 0 Decompression volume (cm ³ ) 0 7.7 15.4 23.2 30.1 Auger speed (rpm) 165 165 165 165 165 Total cycle time (sec) 76.5 76.5 76.5 76.5 76.5 Injection volume (cm ³ ) 92.62 84.91 77.19 69.47 61.75 Decompression time (sec) 20 20 20 20 20

[ 00172 ] The volume of molten foam injected into the polymer cavity was constant, but the density of the molten foam depended on the polymer injection material/decompression volume ratio. The polymer injection material/decompression volume ratios were varied, resulting in parts with the weight and density shown in TABLE 11.

TABLE 11: Test A, Part Weights and Densities Sample Volume of polymer in the drum (cm ³ ) Decompression volume in the drum (cm ³ ) Total injection volume of molten foam (cm ³ ) Polymer injected material as a percentage of total volume (polymer + decompression volume) Decompression time (sec) Weight of the part (g) Density of the part (g/cm ³ ) 1 92 0 92 100% 20 94.1 0.71 2 85 7 92 92% 20 90.4 0.68 3 77 15 92 83% 20 86.0 0.65 4 69 23 92 75% 20 81.8 0.62 5 62 30 92 67% 20 76.1 0.58

[ 00173 ] The results in TABLE 11 show that by decreasing the mass and volume of polymer in the molten foam of the injected material with a commensurate increase in the decompression volume, the density of the resulting part can be varied.

[ 00174 ] Test B

[ 00175 ] In Test B, five molding runs were conducted three times under the same conditions as in Test A; one with a decompression time of 20 seconds (the same as in Test A), one with a decompression time of 70 seconds, and one with a decompression time of 120 seconds. The 15 foam molded parts were weighed and the density was calculated using the mold cavity volume. The density of the parts was plotted as a function of decompression volume for each of the three decompression times. The curves are shown in FIG. 5. As can be seen in FIG. 5, the density of the parts varied as a function of decompression volume. Furthermore, as can be seen in FIG. 5, the longer the decompression time, the denser the part.

Example 4

[ 00176 ] In Example 4, two series of tests were conducted using the MFIM method, Series I and Series II. In Series I, a constant injection speed was used, but the mold closure height was varied. In Series II, the mold closure height was increased with increasing injection speed. In Series II, all conditions were held constant except for the injection speed ( ^cm3 /sec) and the mold closure height. In the tests, LDPE/talc pellets were dry-mixed with a foaming agent and stirred during loading into the molding machine.

[ 00177 ] TABLES 12-13 below show the composition of the injection mixture material and the configuration of the basic mold used for the tests.

TABLE 12: Composition materials Weight % Polymer: LDPE 82% Filler: talc 15% Foaming agent: Hydrocerol® BIH 70 3%

TABLE 13: Basic molding parameters One-piece pan (2 x 4 x 4 inches) (5.08 x 10.16 x 10.16 cm) ASTM Mold Volume of the mold cavity (cm ³ ) 524.39 Sprue volume (cm ³ ) 17.39 Total volume (cm ³ ) 541.78

[ 00178 ] Series I

[ 00179 ] Series I used an injection speed of 394 cubic centimeters per second and conducted three tests, Test A with a mold closure height of 1.02 mm to form Part A; Test B with a mold closure height of 0.76 mm to form Part B; and Test C with a mold closure height of 0.51 mm to form Part C. The settings for the Series I tests are shown in TABLE 14:

TABLE 14: Settings Drum temperature (ºС) 154|185|177|166 Mold temperature (ºС) 20 Injection speed ( ^cm3 /sec) 394 Back pressure (psi) 0 Auger speed (rpm) 165 Auger rotation delay time (sec) 100 Holding pressure (kPa) 0 Holding time (sec) 10 Filling time (sec) 1.78 Mold closing height (mm) 1.02, 0.76, 0.51

[ 00180 ] During each molding cycle (each of Test A, Test B, and Test C), a strain gauge (Kistler Surface Strain Sensor Type 9232A , manufactured by Kistler Holding AG, Winterthur, Switzerland ) was mounted directly above or within the mold cavity. The strain gauge contained two piezoelectric sensors that measured the deformation of the aluminum cavity as a function of time during the molding cycle. The strain measurement was used as a direct measure of the force acting on the mold cavity surface due to the injection of the molten foam and any subsequent additional foaming that occurred within the mold cavity. The cavity strain measurements are shown in FIG. 6 for Test A, clearance height 1.02 mm (line A); Test B, mold closure height 0.76 mm (line B); and Test C, the mold closure height was 0.51 mm (line C). In FIG. 6, the deformation value (block expansion per unit length) was plotted against time in seconds. The deformation curves show that the pressure was higher in Test C than in Test B, and higher in Test B than in Test A.

[ 00181 ] FIG. 7 includes photographic images showing a side view, a top view, an oblique view, and a bottom view of Parts A, B, and C. Parts A and B showed evidence of flattening because the parts did not adequately conform to the mold cavity shape. Part A showed more flattening than Part B. Part C was more fully formed than both Parts A and B in that the edges of Part C were better defined, and Part C conformed better to the contour of the mold cavity, and the interior of the part appeared more uniform.

[ 00182 ] It appears that parts could partially collapse in the cavity during molding if sufficient pressure was not maintained to stabilize the foam in the cavity during curing. Accordingly, in Series II, the mold was closed more tightly at slower injection speeds to maintain sufficient pressure to prevent part collapse during molding.

[ 00183 ] Series II

[ 00184 ] In Series II, the clearance between the mold halves and the mold closing height were systematically reduced as the injection speed was reduced. The molding conditions used were the same as in Series I, except that the injection speeds and mold closing heights used were as shown in TABLE 15:

TABLE 15: Series II Trial Injection speed (cm ³ /sec) Mold closing height (mm) A' 394 +0.51 (clearance) B' 317 +0.21 (clearance) C' 162 -0.26 (compression) D' 85 -0.51 (compression)

[ 00185 ] In Tests A', B', C' and D', four parts were obtained, A', B', C' and D', respectively.

[ 00186 ] Each of Parts A', B', C', and D' was cut into two pieces, and the cross-sections were photographed. The photographic images are shown in FIG. 8. To obtain a part that would not collapse before curing, the mold halves were closed to a greater and greater extent, as shown in TABLE 15, until they were actually pressed together (as shown by the negative dimension value).

[ 00187 ] Parts A', B', C', and D' showed no evidence of flattening, had well-defined edges and surfaces, and appeared quite uniform. Accordingly, the parts were produced using the MFIM method with sharply varying injection speeds by controlling the cavity pressure during injection, for example, by varying the mold closure height.

Example 5

[ 00188 ] Example 5 used the same LDPE composite material as Examples 1-3 in a custom two-cavity mold with molding parameters as shown in TABLES 16-18.

TABLE 16: composition materials Weight % Polymer: LDPE 82% Filler: talc 15% Foaming agent: Hydrocerol® BIH 70 3% LDPE/talc granules were dry mixed with a foaming agent and stirred during loading into the molding machine.

TABLE 17: Basic molding parameters Total volume of the mold cavity 1232 Sprue and sprue passage volume (cm ³ ) 18 Volume of a single mold cavity (cm ³ ) 607

TABLE 18: Specified setting parameters and mold characteristics Injection volume (cm ³ ) 555.7 Decompression volume (cm ³ ) 463.1 Decompression time (sec) 160 Volume filling time (sec) 0.00 Volume filling speed (cm/sec) 0.00 Holding pressure (kPa) 0.00 Holding time (sec) 10.00 Back pressure (kPa) 0.00 Lining (cm) 0.00 Cooling time (sec) 180.00 Sprue breakaway (cm) 2.54 (package) Sprue volume (cm ³ ) 18 Drum temperature (ºС) 163|185|177|166 Mold temperature (ºС) 26.7 Injection speed ( ^cm3 /sec) 394 Auger speed (rpm) 165 Auger rotation delay time (sec) 20 Filling time (sec) 2,385

[ 00189 ] In Example 5, parts 51 shown in FIG. 9 were obtained. During injection, the flow of molten foam entered through the gate 52 and was divided into two separate channels to fill the parts 51 substantially simultaneously. Accordingly, the MFIM method could be used to form parts by dividing the melt into multiple channels in the mold.

Example 6

[ 00190 ] The first part was molded using a 15 wt% talc/85 wt% polycarbonate composite, the composite was mixed with 3 wt% Hydrocerol® XH-901 before loading into the injection molding machine. The first part was molded using the MFIM process. Details of the process are provided in TABLES 19 and 20. The part was molded using a 4 x 2 x 2 (5.08 x 10.16 x 10.16 cm) block mold with a mold cavity volume of 524.4 cm ³ and a sprue volume of 17.4 cm ³ . The sprue was cut from the part and then the part was subjected to X-ray tomography to quantify the cellular structure formed within the 5.08×10.16×10.16 cm geometric shape.

TABLE 19: composition materials Weight % Polymer: polycarbonate 82% Filler: talc 15% Foaming agent: Hydrocerol® XH-901 3%

TABLE 20: Settings Drum temperature (ºС) 288|282|277|260|232|204 Nozzle temperature (ºС) 288 Temperature of loading neck (ºС) 65.5 Mold temperature (ºС) 32 Injection speed ( ^cm3 /sec) 655.48 Specific back pressure (kPa) 6895 Amount of polymer injected material (cm ³ ) 139 Decompression value (cm ³ ) 90 Total injection volume of molten foam (cm ³ ) 229 Auger speed (cm/sec) 7.62 Auger rotation delay time (sec) 40 Approximate decompression time (sec) 80 Holding pressure (kPa) 0 Holding time (sec) 0 Cooling time (sec) 120 Closing force (kN) 267

[ 00191 ] X-ray tomography was performed using a Zeiss Metrotom 800, 130 kV imaging system (Carl Zeiss AG, Oberkochen, Germany). The instrument measured the attenuation of X-rays due to the geometric shape and density components of the material used. Column data were calculated using the Feldkamp reconstruction algorithm, an industry standard method. The instrument had a 1536 × 1920 pixel flat plate detector for a maximum resolution of 3.5 μm under these measurement conditions.

[ 00192 ] An isometric image of a full Zeiss 3D tomographic scan of a first part is shown in FIG. 10, with a continuous portion of the polymer shown as transparent, with cells shaded for visualization, and a section plane A-A shown for a single cross-section. FIG. 11 represents a single cross-sectional plane selected from the X-ray data with threshold analysis provided for discrete cell identification and subsequent quantitative analysis.

[ 00193 ] The roundness values of the cells in the cross-section were obtained. The roundness of these cross-sections was used as a measure of the sphericity of the cells. Accordingly, roundness and sphericity were used interchangeably in the Examples. The quantitative analysis shown in FIG. 12 revealed the distribution of cells by both number and average size as a function of the roundness of each cell. A roundness value of zero indicates a completely non-spherical cell, and a value of 1 represents a perfectly spherical cell. The data showed a distribution of cell sizes and shapes. With the exception of the most deformed cells (designated as 0.1-0.2 on the roundness scale), an inverse relationship was found between the average cell size and the number of cells with a given roundness. In addition, there is an inverse relationship between the average cell size and the number of cells.

[ 00194 ] A second, six-inch (15.24 cm) diameter spherical part was molded using the MFIM process from low density polyethylene (LDPE) using the polymer composition and processing parameters outlined in TABLE 21 and TABLE 22. The LDPE/talc pellets were dry mixed with a foaming agent, Hydrocerol® BIH 70, and mixed while loading into the injection molding machine.

TABLE 21: composition materials Weight % Polymer: LDPE 82% Filler: talc 15% Foaming agent: Hydrocerol® BI-70 3%

TABLE 22: Settings Drum temperature (ºС) 182|174|171|171|166|135 Nozzle temperature (ºС) 182 Temperature of loading neck (ºС) 54 Mold temperature (ºС) 21 Injection speed ( ^cm3 /sec) 655.5 Specific back pressure (kPa) 6895 Amount of polymer injected material (cm ³ ) 574 Decompression value (cm ³ ) 1475 Total injection volume of molten foam (cm ³ ) 2048 Auger speed (cm/sec) 15.24 Auger rotation delay time (sec) 60 Approximate decompression time (sec) 100 Holding pressure (kPa) 0 Holding time (sec) 0 Cooling time (sec) 160 Closing force (kN) 178

[ 00195 ] FIG. 13 is an X-ray tomography image of a cross section of a sphere. As can be seen in FIG. 13, the outer region contained an abundance of small cells with large cells in the central region.

[ 00196 ] FIG. 14 shows a curve of average cell size and average cell number versus average cell roundness, and shows an inverse relationship between average cell size and roundness, and an inverse relationship between average cell size and cell number.

Example 7

[ 00197 ] An MFIM process was used to mold a three-inch (7.62 cm) diameter LDPE composite sphere (92 wt% polymer, 5 wt% talc, and 3 wt% Hydrocerol® BIH 70) with a foam cell structure detailed in FIGS. 15-18. Molding conditions are provided in TABLE 23. The part was molded on an Engel Victory 340 Ton injection molding press in a custom-made water-cooled aluminum mold. The mold cavity volume was 15.38 ⁱⁿ³ (252 ^cm3 ), the shot size was 5 ⁱⁿ³ (82 ^cm3 ), and the decompression volume in the barrel was 5 ⁱⁿ³ (82 ^cm3 ). The decompression time was 77 seconds. The weight of the molded part was 80.31 g, resulting in a final part density of 0.32 g/ ^cm3 .

TABLE 23: Specified setting parameters and mold characteristics Volume filling time (sec) 0.00 Volume filling speed (cm/sec) 0.00 Holding pressure (kPa) 0.00 Holding time (sec) 0.00 Lining (cm) 0.00 Cooling time (sec) 120.00 Sprue breakaway (cm) 2.54 (package) Sprue volume (cm ³ ) 18 Volume of the mold cavity (cm ³ ) 252 Drum temperature (ºС) 180|174|166|160 Mold temperature (ºС) 13 Injection speed (cm/sec) 51 Back pressure (kPa) 689.5 Auger speed (cm/sec) 30.5 Auger rotation delay time (sec) 40 Filling time (sec) 2.38 Closing force (kN) 98

[ 00198 ] After removal from the mold, the part was aged at room temperature for 24 hours, then scratched and immersed in liquid nitrogen for two minutes. After removal from the liquid nitrogen, the sphere was fractured along the scratched surface line, and an image of the fracture surface was obtained using an environmental scanning electron microscope (ESEM) (FEI Quanta FEG 650). The images shown in FIGS. 15-18 are micrographs at different magnifications obtained from the fracture surface of the spherical part using a large field of view photodetector, at a voltage of 5.0 kV and a pressure of 40 Pa.

[ 00199 ] The white block in FIG. 15 denotes the region shown in detail in FIG. 16. The white block in FIG. 16 denotes the region shown in detail in FIG. 17.

[ 00200 ] In FIG. 17, the cells on the left side of the image are large and relatively spherical, while the same cells on the right side of the photograph are seen to become increasingly flattened as they approach the surface of the sphere.

[ 00201 ] The image in FIG. 18 shows in detail the area highlighted by the white block in FIG. 17. As can be seen in FIG. 18, there is a gradual transition from spherical cells to "flattened" or compressed ones as they approach the surface of the part.

Example 8

[ 00202 ] To identify baseline differences between parts produced with standard thicknesses under standard foam molding conditions, a recently published study on standard foam injection molding (Paultkiewicz et al. , Cellular Polymers, vol. 39 , pp . 3–30 (2020)) was used to establish baseline molding parameters using a 16-cycle statistical analysis in a design of experiments (DOE) approach. The material (standard molding grade polypropylene with 0 wt%, 10 wt%, and 20 wt% talc; and 0 wt%, 1 wt%, and 2 wt% Hydrocerol® BIH 70 (foaming agent)) was compounded according to the instructions described in the publication to ensure that the baseline study was simulated as closely as possible. The study was designed to examine the effects of foaming agent concentration, talc content, and process conditions on selected properties of foam injection molded parts. An ISO standard tensile specimen mold with a cavity measuring 4.1 mm in thickness, 10 mm in gauging width, and 170 mm in length was used. No vents were provided for the ISO specimen mold. After ensuring that the injection molding machine, material compositions, and process window were capable of reproducing the results published by Paultkiewicz et al. , a second study was conducted using MFIM-specific process variables, specifically decompression volume and decompression time, while pressure and holding time (important characteristics in the published study) were set to a constant value of zero kN and zero seconds, respectively.

[ 00203 ] Molding was performed using an Engel Victory 340 Ton machine equipped with water cooling. The constant and variable process conditions used are shown in TABLE 24 for both the "standard" foam molding method and the MFIM molding method.

TABLE 24: Constant Setpoints of the Machine and Mold Characteristics Standard molding MFIM molding Variable settings Given experimental variables Low/medium/high levels Foaming agent content (ba) (wt.%) 0/1/2 0/1/2 Talc content (ta) (wt%) 0/10/20 0/10/20 Injection speed ( ^cm3 /sec) 34.4/54.6/74.6 34.4/54.6/74.6 Holding pressure (kPa) 75840/19995 0 Holding time (sec) 2/20 0 Decompression volume (cm ³ ) - 0/7.4/14.7 Decompression time (sec) - 15 Permanent settings Cooling time (sec) 20 Mold temperature (ºС) 20 Injection temperature (ºС) 210 Specific back pressure (kPa) 6895 Cooling time (sec) 20.00 Drum temperature (ºС) 210/210/210/177/163/149/38 Injection volume ( ⁱⁿ³ ) 44.2 29.5

[ 00204 ] The designed study required 16 combinations of processing conditions/polymer composition (16 experimental cycles) for each of the standard and MFIM molding studies. Multiple replicates of each cycle were conducted, producing replicated parts for each experiment. TABLE 25 presents the variations between cycles for both the given standard and MFIM cycles. The cycles were run in a random order to avoid bias. The L/T ratio for the ISO tensile test specimen is 40.5.

TABLE 25 Way molten foam injection molding Standard foam molding method Experiment No. Decompression volume (cm ³ ) Foaming agent (%) Talc content (wt%) Experiment No. Holding pressure
(kPa) Foaming agent (%) Talc content (wt%) 1 0 0 0 1 75842 0 0 2 14.7 0 0 2 75842 0 0 3 0 0 20 3 75842 0 20 4 14.7 0 20 4 75842 0 20 5 7.4 0 10 5 75842 0 10 6 7.4 1 0 6 19995 1 0 7 7.4 1 20 7 19995 1 20 8 0 1 10 8 19995 1 10 9 14.7 1 10 9 19995 1 10 10 7.4 1 10 10 19995 1 10 11 7.4 1 10 11 19995 1 10 12 0 2 0 12 19995 2 0 13 14.7 2 0 13 19995 2 0 14 0 2 20 14 19995 2 20 15 14.7 2 20 15 19995 2 20 16 7.4 2 20 16 19995 2 10

[ 00205 ] After molding 32 unique process combinations of two 16-cycle DOE studies, five specimens of each series were subjected to mechanical tensile strength testing, and images of the fracture surface were obtained after rupture. Representative selected cross-sections of ISO specimens from Runs 10, 11, 14, and 15 by the standard foam molding method are shown in FIG. 19, and representative selected cross-sections of ISO specimens from Runs 9, 10, 15, and 16 by the MFIM method are shown in FIG. 20.

[ 00206 ] The differences between the standard foam molding method as adopted from a recent literature publication and the MFIM method became apparent when the cross-sectional images were examined. The structure in the tensile test specimens produced by the standard method consists of relatively few but well-defined spherical cells located laterally on all sides of a thick region of polymer-free cells. The cross-sectional images of the specimens produced by the standard foam molding method are in good agreement with those reported by Paultkiewicz et al . and are representative of the current industry standard. In contrast, typical cross-sections of ISO test specimens produced by the MFIM method show a cellular structure with more asymmetric, deformed cells.

[ 00207 ] The cells in the cross-section of the MFIM samples also extend to the adjacent surface region in almost all cases, similar to the previous examples described here, and yet they form a much thinner section with a much higher L/T ratio (40.5) than previously described. The results clearly show that the inclusion of the decompression step in MFIM, combined with the exclusion of the standard foam molding process variables of pressure and holding time, result in a significantly different cell structure in the molded parts.

[ 00208 ] Tensile tests were conducted on five replicate parts from MFIM Run 9. FIG. 21 shows a representative cross-section and a series of stress/strain curves for the five tested parts from MFIM Run 9.

[ 00209 ] Tensile tests were conducted on five replicate parts from Run 10, produced by the standard foam molding process. FIG. 22 shows a representative cross-section and a series of stress/strain curves for the five tested parts from Run 10, produced by the standard foam molding process.

[ 00210 ] The average tensile strength of the five MFIM parts from Experiment 9 was lower than the average of the five standard foam molded parts from Experiment 10. However, the MFIM parts exhibited higher strain (elongation) at break.

[ 00211 ] The cross-section of the MFIM part from Run 9 showed more cells (102 cells) than the conventionally molded foam from Run 10 (19 cells).

[ 00212 ] X-ray tomography scans (performed under the conditions described in Example 5) were performed on a randomly selected replicate part from Run 15 using the standard foam molding method (shown in FIG. 23) and on a randomly selected replicate part produced during Run 9 using the MFIM method (shown in FIG. 24). Both FIG. 23 and FIG. 24 show a "top view" taken at 50% depth and a "side view" also taken at 50% depth.

[ 00213 ] In the formed cell structure of the ISO tensile test specimen produced by the standard foam molding method (FIG. 23), the cells were round in shape, and the areas adjacent to the surface of the specimen did not contain cells.

[ 00214 ] In contrast, the ISO tensile test specimen as shown in FIG. 24 includes a large number of elongated cells, and the cells are found in the region adjacent to the surface of the part.

Example 9

[ 00215 ] To study the dependence of the final cell structure under MFIM processing conditions, eight tensile test specimens were molded from LDPE using the MFIM method on an Engel Victory 340 Ton injection molding machine. The mold contained a modified tensile test specimen cavity made of aluminum material measuring 24 cm in length, 2.54 cm in thickness, and a variable width with a 6 cm base length and 2.54 cm base length, tapering to a width of 3.5 cm at the ends. The large tensile test specimen was fed from a cold runner, and the system was actuated through a 1.0 cm diameter door. Material formulations included LDPE with and without talc, always containing 2 wt.% Clariant Hydrocerol® BIH 70 foaming agent. The melt temperature was adjusted to the profile detailed in TABLE 26, and the residence time in the barrel was 13 minutes before the injection material was accumulated for injection. After the injection material had accumulated, the screw was retracted to create a decompression volume of either 4.0 cubic inches (66 ^cm3 ) or 6.0 cubic inches (98 ^cm3 ), and the LDPE/foaming agent mixture was allowed to foam for either 15 or 45 seconds in the empty space of the drum before injection. The study was conducted for both unfilled LDPE and LDPE filled with 15% talc. Details of the process conditions are shown in TABLE 26.

TABLE 26: Constant set-up settings and mold characteristics for large MFIM tensile test specimen Given experimental variables Low/High Levels Talc content (wt%) 0/15 Decompression volume (dv) (cm ³ ) 66/98 Decompression time (dt) (sec) 15/45 Permanent settings Foaming agent content (wt.%) 2 Cooling time (sec) 60 Mold temperature (ºС) 10 Injection temperature (ºС) 182 Injection speed ( ^cm3 /sec) 328 Specific back pressure (kPa) 6895 Cooling time (sec) 60.0 Drum temperature (ºС) 210/210/210/177/163/149/38 Injection volume (cm ³ ) 98 Closing force (kN) 89

[ 00216 ] FIG. 25 shows an X-ray scan of one of the parts in this study, depicting the general shape of each part.

[ 00217 ] FIG. 26 depicts a cross-section of each test specimen molded in the study, cut from the middle of the gauge length, with the specified variable parameters. The set of specimens includes two main groups: specimens produced with talc and specimens produced without talc. In FIG. 26, the set of specimens on the left side depicts those parts that were produced without talc. These parts exhibit a structure of finer cells in the core of the part, and the integrity of the resulting cell structure is substantially unaffected by changes in the decompression amount and decompression time, indicating that all decompression amounts and durations were within an acceptable range.

[ 00218 ] The sample set on the right shows those samples containing 15 wt.% talc. Some smearing on the part surfaces was caused by knife damage to the low-modulus LDPE and is not characteristic of the part quality. The cell structure in the talc-containing parts was correspondingly larger, and the cell roundness was slightly lower than in the talc-free equivalents.

[ 00219 ] An X-ray tomography image was obtained from a cross-section of the major surface of approximately 50% of an MFIM part produced with 15 wt.% talc, a decompression volume of 6 in ³ (98 cm ³ ), and at 15 seconds of decompression time. The image is shown in FIG. 27.

Example 10

[ 00220 ] A tensile test specimen part was produced using a standard foam molding process from LDPE containing 15 wt.% talc as a filler and 2 wt.% Hydrocerol® BIH 70, using the process parameters described in Example 9, but without the MFIM decompression step. This part from the standard foam molding process was compared to the MFIM part formed with 15% talc, a decompression volume of 6 ⁱⁿ³ (98 ^cm3 ), and at a decompression time of 15 seconds, from Example 9. Using the methods described in Example 6, X-ray tomography images were obtained of the central portion of each of the parts (MFIM molding and standard foam molding) at varying depths from the main surface. Cross-sectional images were also recorded. The images are shown in FIG. 28.

[ 00221 ] X-ray tomography analysis of the cell number, cell circularity, and average cell size (the longest dimension of a cell) was performed on images of each part as a tensile test specimen (MFIM materials and standard method materials) at each depth from the main surface. The cell number, cell circularity, and average cell size were plotted in each case as curves versus the cross-sectional depth; and the corresponding curves are shown in FIGS. 29-31, respectively.

[ 00222 ] As shown in FIG. 29, the number of cells was higher in the MFIM-molded part at all depths. As can be seen from all of the Examples and Figures, the part molded using the standard foam molding method appears to be cell-free or substantially cell-free in the region, or "skin," close to the surface, such as within about the first 2.5 mm of depth from the main surface, whereas cells are present in the part molded using the MFIM method within the region between about 2.5 mm below the surface and at the surface.

[ 00223 ] As shown in FIG. 30, in general, the cell roundness was greater in the sample formed by the standard foam molding process than in the MFIM molded part, except in the middle of the MFIM part, where the roundness was also high in the MFIM molded sample.

[ 00224 ] As shown in FIG. 31, the cell size was generally larger in the tensile test specimen formed by the standard foam molding method, but quickly decreased to zero in areas near the outer surfaces (e.g., within 2.5 mm from the surface). In contrast, the cell size was more uniform throughout the depth of the MFIM-molded part, and the cells continued all the way to the surface.

[ 00225 ] The same trends are observed from visual inspection of the cross-sections shown in FIG. 28. Within 2.5 mm from any outer surface, the standard foam molded part appears to be cell-free, whereas cells are discernible on the outer surface in the MFIM part.

Example 11

[ 00226 ] A large sample of ocean-caught plastic for reclamation was analyzed using differential scanning calorimetry and estimated to contain approximately 85 wt% HDPE, with the remainder comprising polypropylene and contaminants.

[ 00227 ] Two parts were successfully molded from ocean-recovered plastic using the MFIM method into a 4 x 4 x 2 (1.57 x 1.57 x 0.79 cm) block and a 15.24 cm diameter sphere. Molding was performed using an Engel Duo 550 Ton injection molding machine (Engel Machinery Inc., York, PA, USA). Both parts were center-gate and filled with viscous spiral-fold flow.

[ 00228 ] The technological parameters and characteristics of the obtained part are listed in TABLE 27 and TABLE 28, respectively.

TABLE 27 6-inch sphere Block, 4×4×2 (inches) Material Plastic from the ocean Plastic from the ocean Device Engel Duo 550 Ton Engel Duo 550 Ton Decompression volume (cm ³ ) 819 295 Decompression time (sec) 340 60 Foaming agent BIH 70 (weight%) 3 3 Cooling time (sec) 400 120 Mold temperature (ºС) 35 38 Injection temperature (ºС) 204 204 Injection speed ( ^cm3 /sec) 655 787 Specific back pressure (kPa) 6895 13790 Drum temperature (ºС) 204/191/177/163/149/107/54 Injection volume (cm ³ ) 1229 279 Closing force (kN) 445 445 Holding time (sec) 0 0 Holding pressure (kPa) 0 0

TABLE 28 Part specifications 6-inch sphere Bar Weight of the part (g) 921.6 253.2 Volume (without sprue) (cm ³ ) 1856 524.3 Density of the part (g/ ^cm3 ) 0.496 0.482

Example 12

[ 00229 ] A nine-inch (22.86 cm) diameter sphere, Sample 10, was molded using the MFIM method described herein. In addition, a second nine-inch (22.86 cm) diameter sphere, Sample 20, was molded using a variation of the method. The variation of the method, referred to herein as the "reverse MFIM" method, was as follows:

[ 00230 ] A) A mixture was formed by mixing a polymer (which may be in the form of grains, powder, beads, granules, etc.) with a chemical blowing agent and any other additives such as filler. The mixture was introduced into the injection block and the rotating screw of the injection block was driven, propelling the material forward in the barrel of the injection molding machine, thereby forming a heated flowable material in accordance with normal injection molding techniques. B) The screw was retracted toward the feed hopper, intentionally creating a space between the screw and the nozzle inside the barrel. C) A predetermined volume of material was metered into the front of the barrel in the injection block by rotating the screw, thereby propelling the predetermined volume from the feed zone to the front of the screw and into the special space created in step B. During this feeding stage, the screw rotated to propel the molten material forward into the space in the barrel between the screw and the nozzle, thereby creating a predetermined volume. However, this predetermined volume occupied only a portion of the designated space, thereby creating a volume for the injected material to transform into foam and expand, i.e., the decompression volume. D) The material remained in the barrel between the screw and the nozzle for a period of time, here referred to as the "decompression time." During the decompression time, the material expanded due to foaming, filling or partially filling the space created in stage (B). E) The molten foam was injected into the mold cavity by the forward advancement of the screw and/or the rotation of the screw.

[ 00231 ] The regular and reverse MFIM methods thus differ from each other in that in the MFIM method, the screw was rotated to introduce the injection material into the front of the barrel before the screw was retracted to form a decompression space; whereas in the reverse method, the screw was retracted to form a decompression space before the screw was rotated to introduce the mass of injection material into the created special space.

[ 00232 ] Both Sample 10 and Sample 20 were molded from virgin LDPE containing 2% Hydrocerol® BIH 70, 2% talc, and 1% yellow colorant. Molding was performed on an Engel Duo 550 Ton injection molding machine (Engel Machinery Inc, York, PA, USA). The mold had a spherical cavity within an aluminum mold with cold runner and gate feed.

[ 00233 ] Technological parameters are shown in TABLE 29:

TABLE 29 Sample 10 Sample 20 Processing method MFIM Inverse MFIM Injection volume (cm ³ ) 1639 1762 Decompression volume (cm ³ ) 1475 1475 Thick paste (cm ³ ) 3114 3236 Injection to decompression volume ratio 10:9 10:9 Cooling time (sec) 300 300 Auger rotation delay time (sec) 140 140 Dosing capacity ( ^cm3 /sec) 32.8 32.8 Decompression rate ( ^cm3 /sec) 164 164 Approximate decompression time (sec) 101 106 Closing force (kN) 89 89 Specific back pressure (kPa) 6895 6895 Injection pressure (kPa) 52476 53827 Injection speed ( ^cm3 /sec) 655 655 Auger speed (cm/sec) 15.24 15.25 Mold temperature (ºС) 10 10 Weight of injected material (g) 1334 1335

[ 00234 ] The density of the parts in both Sample 10 and Sample 20 was 0.214 g/ ^cm3 , a density reduction of 77% in both cases.

[ 00235 ] A photograph of Sample 20 is shown in FIG. 32, and Sample 10 in FIG. 33, with each spherical part mounted on a stand. As can be seen in the Figures, Sample 20, produced using the "inverse MFIM method," exhibited an uneven surface, while the surface of Sample 10, produced using the MFIM method, was much smoother. The average wrinkle depth was evaluated using an optical microscope and X-ray tomography. The average wrinkle depth was measured to be less than 50 microns (μm) for Sample 10, but 565 microns (μm) for Sample 20.

[ 00236 ] Each of Sample 10 and Sample 20 was cut in half along the maximum diameter to create a cross-section. The cross-section of the four pieces was photographed. One half of Sample 20 formed by the inverse MFIM process is shown in the image in FIG. 34, and one half of Sample 10 is shown in FIG. 35. Closer inspection of the edge revealed that in Sample 10 and Sample 20, the cells were located just at the surface, for example, within 2.5 mm from the surface, unlike parts produced elsewhere in the Examples by the standard foam molding process.

[ 00237 ] X-ray tomography examination was performed on the first inch of sample depth for Sample 10 and Sample 29, and using the methods described in Example 6, the number of cells and the cell size were measured for various distances from the surface of each sample. The curves are shown in FIGS. 36 and 37, in which "MFIM" refers to Sample 10, and "inverse MFIM" refers to Sample 20.

[ 00238 ] Two additional spherical parts, Parts 6 and 7, were produced under the same conditions and from the same polymer/talc/colorant/foaming agent mixture as Sample 10, i.e., by the MFIM method. Five parallelepiped-shaped pieces, each approximately 2 inches by 2 inches by 1 inch, were cut from each of Parts 6 and 7 and tested for bulk modulus (stress versus strain). The average stress versus average strain (MFIM method) is shown by the curves in FIG. 38.

[ 00239 ] Two additional spherical parts, Parts 22 and 24, were produced under the same conditions and from the same resin/talc/colorant/foaming agent mixture as Sample 20. Five parallelepiped-shaped pieces, each approximately 2 inches by 2 inches by 1 inch (about 5.1 cm by 5.1 cm by 5.1 cm), were cut from each of Parts 22 and 24 and tested for bulk modulus (stress versus strain). The average stress versus average strain (inverse MFIM) is also shown by the curves in FIG. 38. As can be seen in FIG. 38, the bulk modulus of the MFIM parts (average of Parts 6 and 7) and the inverse MFIM parts (average of Parts 22 and 24) are similar.

[ 00240 ] Five strips were cut from each of Parts 6 and 7 (MFIM) and 22 and 24 (reverse MFIM). Each strip had approximate dimensions of 1 inch by 1 inch by 8 inches. The flexural modulus (stress versus strain) was measured for all of the strips, and the results were averaged for the ten MFIM strips and the results were averaged for the ten reverse MFIM strips. The results are shown as curves in FIG. 39.

Example 13

[ 00241 ] Parts were manufactured using MFIM methods as described herein, with various shapes and materials, as shown in TABLE 30. The parts were cut into sections. In all cases, the region near the surfaces included smaller cells, but the cell size increased as they moved away from the surface. The region of smaller cells closer to the surfaces transitioned to larger cells as they moved away from the surface. While the transition was gradual, and thus there was no distinct small-cell layer and a distinct larger-cell layer, the relative areas of the small, or "compressed," cell region and the larger cell region were visually estimated using microscopy and confirmed by light microscopy and are shown in TABLE 30. While the numbers were only estimates, examination of the images revealed that the depth of the region and the percentage of the region that was occupied by "compressed" cells varied widely, possibly depending on the part shape, material, and/or experimental conditions.

TABLE 30 Material Filler Sphere diameter (inches) Estimated core percentage Estimated percentage of compressed area LDPE - 3 in the sphere 91% 9% LDPE 15% talc 3 in the sphere 80% 20% Nylon 6 15% talc 3 in the sphere 85% 15% LDPE 15% talc 6 in the sphere 87% 13% LDPE - 6 in the sphere 85% 15% High impact polystyrene 15% talc 6 in the sphere 85% 15% Material Filler Geometry (inches) Estimated core percentage Estimated percentage of compressed area Metallocene polyethylene - 4×4x2 66% 34% High impact polystyrene 15% talc 4×4x2 53% 47% ABS 20% talc 4×4x2 71% 29% Material Filler Geometry Estimated core percentage Estimated percentage of compressed area LDPE - Large tensile test specimen 54% 46% LDPE 15% talc Large tensile test specimen 73% 27% Material Filler Geometry Estimated core percentage Estimated percentage of compressed area Polypropylene 10% talc ISO tensile test specimen 65% 35%

Example 14

[ 00242 ] The first part was molded using a composition of 98 wt% metallocene polyethylene blended with 2 wt% Hydrocerol® BIH 70 before loading into the injection molding machine. The first part was molded using the MFIM process. Processing details are provided in TABLE 31 and TABLE 32. The part was manufactured using a 2 x 4 x 4 (5.08 x 10.16 x 10.16 cm) block mold with a mold cavity volume of 524.4 cm ³ and a sprue volume of 17.4 cm ³ . The sprue was cut from the part and then the part was subjected to a compression load test to quantify the compressive strength characteristics of the cellular structure formed within the 2x4x4 geometry (in inches).

TABLE 31: Material composition Weight % Polymer: Metallocene polyethylene 98% Foaming agent: Hydrocerol BIH 70 2%

TABLE 32: Settings Drum temperatures (°C) 204|193|188|188|177|166|166| Nozzle temperature (°C) 204 Temperature of loading neck (ºC) 49 Mold temperature (ºС) 55 Injection speed ( ^cm3 /sec) 655.48 Specific back pressure (kPa) 10342 Amount of polymer injected material (cm ³ ) 245.8/327.7/409.7 Decompression value (cm ³ ) (for samples A/B/C) 360.5/163.9/81.9 Auger speed (cm/sec) 7.62 Auger rotation delay time (sec) 100/740/740 Approximate decompression time (sec) 60 Holding pressure (kPa) 0

[ 00243 ] Compression testing was performed using an Instron Universal Testing System (Instron USA, Norwood, MA, USA). Each molded foam block was placed between test platens and stabilized in a climatic testing chamber at 30ºC for five minutes prior to testing. The system was equipped with a 250 kN load cell. The compression testing speed was 5 mm/min.

[ 00244 ] The results showed that the bulk modulus was 19 MPa for sample A (0.37 g/cm ³ ), 39 MPa for sample B (0.45 g/cm ³ ), and 55 MPa for sample C (0.57 g/cm ³ ). As shown in FIG. 40, the compressive strength of the metallocene polyethylene (mPE) blocks increases with increasing density.

Claims (42)

1. An article made of thermoplastic polymer foam having a continuous matrix of thermoplastic polymer that forms a plurality of air cavities throughout the entire length of the article, wherein a surface region of the article extending 500 microns (µm) from the surface of the article includes compressed air cavities throughout its entire length. 2. The product according to paragraph 1, wherein the product also includes additional compressed pneumatic cavities located more than 500 microns (µm) from its surface. 3. The article according to claim 1 or 2, wherein the thermoplastic polymer is selected from polyolefins, polyamides, polyimides, polyesters, polycarbonates, polylactic acids, acrylonitrile-butadiene-styrene copolymers, polystyrenes, polyurethanes, polyvinyl chlorides, tetrafluoroethylene copolymers, polyether sulfones, polyacetals, polyaramids, polyphenylene oxides, polybutylenes, polybutadienes, polyacrylates and methacrylates, ionomeric polymers, block copolymers of polyethers and amides, polyarylether ketones, polysulfones, polyphenylene sulfides, polyamide-imide copolymers, polybutylene succinates, cellulose materials, polysaccharides or their copolymers, alloys, compounds and mixtures. 4. The article according to claim 1 or 2, wherein the continuous polymer matrix comprises a polyolefin, a polyamide, an olefin copolymer with ionic functional groups, or a block copolymer of a polyether and an amide. 5. The article according to any one of claims 1 to 4, wherein the continuous polymer matrix comprises a stream of mixed plastic waste. 6. An article according to any one of claims 1 to 5, wherein the continuous polymer matrix further comprises one or more additional materials selected from coloring agents, stabilizers, brighteners, nucleating agents, fibers, dispersed materials and fillers. 7. An article according to any one of claims 1 to 5, wherein the continuous polymer matrix further comprises talc or a coloring agent, or both talc and a coloring agent. 8. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 2 cm. 9. An article according to any of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 5 cm. 10. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 10 cm. 11. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a volume of over 1000 ^cm3 . 12. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a volume of over 5000 ^cm3 . 13. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 2 cm and a volume of more than 1000 ^cm3 . 14. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 5 cm and a volume of more than 1000 ^cm3 . 15. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 5 cm and a volume of more than 5000 ^cm3 . 16. An article according to any one of paragraphs 1-7, wherein the article made of polymer foam has a thickness of more than 10 cm and a volume of more than 5000 ^cm3 . 17. An article according to any one of paragraphs 1-16, including a reduction in density by an amount from 30% to 85%. 18. An article according to any one of paragraphs 1-17, having a void ratio of 5% to 70%. 19. An article according to any one of paragraphs 1-18, wherein the article is a spheroid. 20. An article according to any one of paragraphs 1-18, wherein the article is a rectangular parallelepiped. 21. An article according to any one of paragraphs 1-18, wherein the article has the shape of a dumbbell, the shape of a cutlery item, the shape of a decorative globe having protruding geographical elements, the shape of a person, the shape of an animal or insects, the shape of a frame or case suitable for placing screws, bolts and the like in the article. 22. The article of claim 19, wherein the polymer foam spheroid has a diameter of 3 inches (7.62 cm) to 6 inches (15.24 cm) and a density that is 35% to 85% less than the density of the spheroid in the absence of air cavities. 23. The article according to claim 19, wherein the spheroid made of polymer foam has a density that is 50% to 85% less than the density of the spheroid in the absence of air cavities. 24. The article of claim 20, wherein the polymer foam parallelepiped has a minimum dimension of about 1 inch (2.54 cm) and a density that is 35% to 85% less than the density of the parallelepiped in the absence of air cavities. 25. The product according to claim 20, in which the parallelepiped made of polymer foam has a density that is 50% to 85% less than the density of the parallelepiped in the absence of air cavities. 26. The article of any one of claims 20, 24, or 25, wherein the polymeric foam parallelepiped has dimensions of about 1 inch (2.54 cm) by 1 inch (2.54 cm) by 2 inches (5.08 cm), or about 1 inch (2.54 cm) by 4 inches (10.16 cm) by 11 inches (27.94 cm), or about 1 inch (2.54 cm) by 4 inches (10.16 cm) by 17 inches (43.18 cm), or about 1 inch (2.54 cm) by 12 inches (30.48 cm) by 12 inches (30.48 cm), or about 2 inches (5.08 cm) by 2 inches (5.08 cm) by 2 inches (5.08 cm), or about 2 inches (5.08 cm) by 4 inches (10.16 cm) by 11 inches (27.94 cm), or about 2 inches (5.08 cm) by 4 inches (10.16 cm) by 4 inches (10.16 cm), or about 4 inches (10.16 cm) by 4 inches (10.16 cm) by 4 inches (10.16 cm), or about 12 inches (30.48 cm) by 12 inches (30.48 cm) by 12 inches (30.48 cm). 27. A method for forming an article from polymer foam, wherein the method includes: heating and mixing a thermoplastic polymer and a pneumatogen source to form a molten pneumatic mixture, wherein the temperature of the molten pneumatic mixture exceeds the temperature at which the pneumatogen source forms a pneumatogen at atmospheric pressure, and the pressure applied to the molten pneumatic mixture is sufficient to substantially prevent the formation of air voids; accumulation of the selected amount of molten pneumatic mixture in the collection zone; creating a volumetric expansion in the collection zone near the molten pneumatic mixture to form molten polymer foam from the molten pneumatic mixture; dispensing molten polymer foam from a collecting area into a cavity formed in a mold, wherein the molten polymer foam contacts the surface of the mold forming the cavity; and cooling the molten polymer foam in the mold cavity to form a cured polymer foam product. 28. The method according to claim 27, wherein the dosing comprises partially filling the cavity of the mold. 29. The method of claim 27, wherein the dosing comprises essentially filling a cavity of a mold. 30. The method according to claim 27, wherein the dosing comprises completely filling the cavity of the mold. 31. The method according to any one of paragraphs 27-30, in which the heating, mixing, accumulation, forming and dosing are carried out using an injection molding device. 32. The method according to any one of claims 27-31, wherein the pneumatogen source is an organic compound. 33. The method according to any one of claims 27 to 31, wherein the source of the pneumatogen is a pneumatogen. 34. The method according to any one of claims 27 to 32, wherein the pneumatogen is CO ₂ or N ₂ . 35. The method according to any one of claims 27 to 34, wherein dispensing molten polymer foam from an extruder into a cavity formed by a mold includes allowing the molten polymer foam to flow freely into the cavity, wherein the free flow provides one or more of a swirling molten stream or a folded molten stream within the cavity. 36. The method of claim 35, wherein the free flow is a flow under pressure. 37. The method according to any one of claims 27 to 36, wherein the mold is an aluminum mold.