WO2017093865A1 - Biodegradable composite material of natural manicaria saccifera fibre and polylactic acid and production method thereof - Google Patents

Abstract

The present invention relates to a composite material formed from a thermoplastic reinforced with a natural fibre, and to the production method thereof. More specifically, the invention relates to a composite material reinforced with natural fibre extracted from the bract of the Manicaria saccifera palm, using a polylactic acid thermoplastic as a polymer matrix, and to the method for producing same by means of the chemical treatment of the fibre and heat compression moulding.

Description

 BIODEGRADABLE COMPOSITE MATERIAL OF NATURAL FIBER OF MANICARIA SACCIFERA AND POLY-LACTIC ACID, AND ITS METHOD OF

 MANUFACTURING

FIELD OF THE INVENTION

The present invention relates to a biodegradable composite material which, thanks to its structural capacity and competitive mechanical properties in relation to conventional synthetic compounds, can be used as a manufacturing material for different elements in the automotive and construction sector, in the sector of protection and packaging and for the realization of sports goods.

Particularly, in the automotive sector it can be used in the manufacture of door panels, seat backs, ceilings, panels, trunk interiors and insulating modules. In the construction sector, doors, terraces, railings, window frames, boards, ceilings, walls and floors can be made. Additionally, rackets, bicycle frames, surfboards, snowboards, skis and hockey skates can be made with this material. For protection and packaging, cell phone cases, laptop cases, musical instrument protection cases and coffins can be manufactured.

Additionally, the biodegradable composite material of the present invention can be used in the manufacture of chairs, decorative items, musical instruments and luxury item design. STATE OF THE TECHNIQUE

As a result of the growing environmental awareness, new and increasingly stringent legislation aimed at environmental protection, and added to the high costs of oil and its derivatives, worldwide initiatives to design and manufacture products have been developed in recent years. More friendly with the environment. Products that favor biodegradation or recycling processes after their life cycle have been imposed on traditional materials, so that sustainable materials and production processes have been implemented that contribute to the reduction of solid waste accumulation. These processes have been based on the research and development of materials of natural origin, trying to replace materials derived from petroleum or mining processes that produce great environmental impacts and harm not only the environment but also human health.

One of the sustainable proposals with the greatest potential that have been developed in recent years are biodegradable composite materials of natural origin. These composite materials, formed by the union of a biodegradable polymer matrix and natural fibers, have great potential due to their biodegradable ecological character that has captured the attention of the industrial sector interested in complying with the environmental regulations imposed.

Several proposals for this type of materials are found in the state of the art. For example, document CN101333330A describes a biodegradable composite material of polylactic acid (PLA) and its method of manufacturing by hot compression. The compound is made up of polylactic acid resin reinforced with a natural fiber modified with a silane type coupling agent. While the silane coupling agent allows the manufacture of compounds with some natural fibers, such as bamboo, linen, sisal, jute, hemp, bamboo fiber, corn stubble, straw Wheat, rice straw, rice bran, coconut husks, peanut and pine husks, using this coupling agent does not improve the properties of the PLA composite material in all cases of natural fiber reinforcements. In some cases, when natural fibers have a superficial presence of lignin, impurities, fats, and other substances, the effectiveness of the coupling agent is very limited to improve the mechanical properties of the compound. Specifically, for natural fibers with abundant surface content of impurities and substances, when a silane-type coupling agent is used, the reaction between the silico-functional group of the silane and the fiber is limited, reducing the interaction of the silane with the hydroxyl groups of cellulose This lack of interaction limits the adhesion between the fiber and the PLA resin, which in many cases leads to a decrease in the mechanical properties of the composite material.

In addition, document CN101333330A describes the manufacturing method for the biodegradable composite material from PLA and natural fibers. This document reports a hot compression molding using molding pressures between 5 and 30 MPa. Although it is a wide range of molding pressures, for the manufacture of PLA composite materials using naturally occurring woven fibers, these pressures are too high and are not suitable for the manufacture of the compound. High pressures cause the woven fiber structure to deform and lose its structural integrity, as well as its mechanical strength.

Thus, although document CN101333330A describes a biodegradable compound reinforced with various traditional natural fibers in the form of short fibers and its method of manufacturing by hot compression molding, it does not mention or suggest the use of natural fabrics that offer high structural capacity and mechanical properties. competitive. On the other hand, the manufacturing method described does not consider the use of natural fabrics. In the same line of biodegradable composite materials is document CN102167895A. This describes the method of manufacturing a polylactic acid compound reinforced with wool fibers. This compound, designed to be used as a thermal and / or acoustic insulator, takes advantage of the thermal and acoustic properties of wool to manufacture a completely biodegradable product with great insulating capabilities of structures and vehicles. This compound is manufactured in sheets by hot compression molding under pressures between 4 and 10 MPa at temperatures between 170 and 180 ° C.

Although the sheet of biodegradable composite material of PLA and wool of document CN102167895A has very good physical properties in terms of acoustic and thermal insulation, its structural properties in terms of its mechanical resistance are not very good due to the low load capacity of the fiber Wool reinforcement. Consequently, given the low structural requirements, the manufacturing method described in this patent application does not incorporate in its process a chemical or physical treatment to the natural reinforcing fiber, necessary treatment in structural natural compounds to improve the interfacial bond between the matrix and fiber and raise the final mechanical strength. Similarly, the molding pressures used in this manufacturing method are specific for the use of short wool fibers, in particular the molding pressures are very high for compounds reinforced with natural fiber fabrics because it is not necessary to protect the structural integrity of the tissue.

Additionally, CN 103073863 discloses a composite sheet made from natural fiber and polylactic acid. In the described method, a natural fiber surface treatment is performed by immersion in an aqueous solution of a silane coupling agent, an aqueous solution of sodium hydroxide or potassium permanganate in acetone for 1 to 6 hours. For the production of the composite material, the treated natural fiber is uniformly introduced into a molten mass of poly-lactic acid modified by an unsaturated anhydride terminal group and the polymerization reaction is initiated by solar radiation or polymerization reaction by a free radical initiator. However, this method has the disadvantage of incorporating non-environmentally friendly materials into its process. In addition, the composite material obtained does not have very competitive properties to be implemented in industrial processes. On the other hand, it is necessary to highlight that this document presents significant conceptual errors that make its manufacturing unfeasible. For example, the document states that the matrix of the polylactic acid composite is a thermostable polymer for which a curing process is described. It is well known that the polylactic acid polymer is a thermoplastic that does not require curing or polymerization processes for its implementation in composite materials.

Other prior art document such as CN101 121813 refers to a composite sheet made from a natural fiber and polylactic acid. The method of preparing the composite sheet comprises the steps of selecting a quantity of natural fibers impregnated with an aqueous solution of a coupling agent for 1 to 100 minutes, drying the natural fiber and performing compression in mold of the polylactic acid together with the treated at a temperature between 100 and 160 ^and C. However natural fiber, although the material obtained by the method described herein is fully biodegradable, it said previously not mention or suggest the use of natural materials that offer high structural ability and properties competitive mechanics.

On the other hand, regarding the use of natural fiber extracted from the palm of Manicaría saccifera as reinforcement in composite materials, the authors Oliveira and d'Almeida (Journal of Composite Materials, 2014, 48 (10): 1 189-1 196 ) have a composite material of thermosetting resins reinforced with the fiber of Manicaría saccifera. This document describes the use of Manicaría saccifera natural fiber as a reinforcement for two thermostable polymers like polyurethane and epoxy resin. However, although this document describes the use of fiber extracted from Manicaría saccifera as a reinforcement in composite materials, the compound described in this article presents comparative disadvantages with the state of the art of natural compounds. First, despite using a natural fiber, the use of non-biodegradable thermosetting resins makes it a material that is not very environmentally friendly. The thermostable polymers used herein are long chains of molecules that form three-dimensional network structures, making them non-biodegradable and even non-recyclable materials. Likewise, the mechanical performance exhibited by the described composite material is not exceptional in comparison with other natural compounds, and even is far from traditional synthetic compounds, discouraging its use in various applications. For example, this article reports a maximum flexural strength of 53.1 MPa for epoxy resin reinforced with Manicaría saccifera, a lower value than the flexural strength achieved by other natural compounds, and significantly less than the value of resistance to flexion achieved by the biodegradable natural compound of the present invention (209 MPa). This lower mechanical behavior may be due to the fact that the manufacturing method used for this composite material is not correct to take advantage of the high load bearing capacity of Manicaría saccifera fiber.

In this way, despite the advances made in the state of the art for obtaining biodegradable natural composite materials and for the use of Manicaría saccifera palm fiber as a reinforcement in conventional synthetic compounds, it is clear that there was a need to develop a completely biodegradable natural compound with structural capacity and competitive mechanical properties, which would allow replacing traditional materials with more environmentally friendly materials and thus meet the new market requirements. Thus, the present invention provides a biodegradable composite material suitable for the preparation of materials that comply with legal and market requirements, in terms of environmental protection, superior mechanical resistance to similar natural compounds, and competitive mechanical properties with traditional materials (for example, fiberglass reinforced compounds). In addition, the present invention provides a method of manufacturing the biodegradable composite material, which favors the interaction and bonding between the matrix and the reinforcing fiber to optimize the mechanical properties of the final composite material.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 . Scheme of the biodegradable composite material reinforced with natural fiber of Manicaria saccifera and thermostable polymer matrix of polylactic acid.

 Figure 2. Example photograph of different shapes, geometries and thicknesses that the material of the present invention can take according to its particular application.

Figure 3. Photograph of the biodegradable composite material reinforced with natural fiber of Manicaria saccifera and thermostable polymer matrix of poly-lactic acid and its raw materials.

Figure 4. Flow chart of the manufacturing method of the biodegradable natural compound of palm fiber reinforced poly-lactic acid

Manicaria saccifera.

 Figure 5. Scanning electron microscope (SEM) micrographs of Manicaria saccifera (a-b) fiber without chemical treatment and (c-f) chemically treated with the method of the present invention.

Figure 6. Scanning electron microscope (SEM) micrographs of the fracture surface of stress tests of the biodegradable composite material reinforced with natural fiber of Manicaria saccifera and thermostable polymer matrix of poly-lactic acid (ab) manufactured with untreated fiber and (cf) manufactured with the method of the present invention.

Figure 7. Comparative graph of the tensile strength of the biodegradable natural compound of the present invention with other biodegradable natural compounds made from polylactic acid and different natural fibers.

Figure 8. Comparative graph of the flexural strength of the biodegradable natural compound of the present invention with other biodegradable natural compounds made from polylactic acid and different natural fibers.

Figure 9. Comparative graph of the impact resistance of the biodegradable natural compound of the present invention with other biodegradable natural compounds made from polylactic acid and different natural fibers.

Figure 10. Comparative graph of the tensile and flexural mechanical resistance of the biodegradable natural compound manufactured by the method of the present invention, the method without including pretreatment of the fiber and non-reinforced PLA.

Figure 1 1. Comparative graph of the specific tensile and flexural mechanical strengths of the biodegradable natural compound of the present invention with traditional structural fiberglass compounds.

 Figure 12. Comparative graph of the acoustic absorption coefficient of the biodegradable natural compound of the present invention with expanded polystyrene (non-biodegradable or recyclable material typically used for acoustic insulation applications).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a completely biodegradable natural composite material manufactured based on a thermoplastic polymer resin, biodegradable and from renewable sources, reinforced with a fiber of plant origin in the form of natural non-woven. Specifically, the material of the present invention is composed of a polymeric matrix of polylactic acid (PLA), reinforced with natural fiber extracted from the bract of the Manicaria saccifera palm, a combination that provides exceptional physical and mechanical properties.

The material of the present invention, shown schematically in Figure 1, is typically presented in the form of panels (1), being able to take different shapes, geometries and thicknesses according to its particular application, as shown in Figure 2. Its composition of Manicaria saccifera fiber (2) and polylactic acid (3) may vary according to mechanical and physical requirements in proportions of fiber to PLA ratio between 10% and 95% by weight, which determines the density and mechanical properties and Physics of the final material. The biodegradable composite material can also include dyes to dye the fiber of Manicaria saccifera as well as the matrix of polylactic acid in a proportion between 0.1% and 15%. Other additives such as dyes, UV stabilizers, antistatic agents, flame retardants, among others, can also be included in the composite material to improve its properties. For example, the dyes and additives used included in the composite material should be selected so as not to affect the biodegradable nature of the compound.

Manicaria saccifera palm bract fiber is a lignocellulosic fibrous material with crosslinked individual fibers that resemble a natural fabric with a particular fabric design. This natural fabric, which is used as a natural reinforcement in the composite material of the present invention, exhibits an intrinsic loading capacity, which, in combination with the manufacturing process developed, effectively engages with the polymeric matrix of PLA to achieve mechanical resistance Notable composite material. Due to these exceptional mechanical properties, the natural compound presented stands out within the biodegradable composite materials allowing its structural and non-structural application in various industrial sectors such as automotive, construction, decoration, among others.

In particular, unlike other natural compounds that typically use short, unidirectional fibers or manufactured fabrics, in the manufacturing method of this invention the natural fiber of the bract of the Manicaria saccifera palm is used as reinforcement for the polymeric matrix structure. Thus, the manufacturing method, in combination with the natural design that this fiber presents, contributes to achieve unexpected mechanical and physical properties.

In addition to its exceptional physical and mechanical properties, the natural compound of the present invention exhibits environmentally friendly properties. First, its polymeric matrix comes from renewable natural sources and is completely biodegradable. In addition, its fiber reinforcement comes from plant sources as a byproduct of palm. During the harvest of the bract from which the fiber is extracted, the palm is not destroyed or its cyclonatural is interrupted, which makes its production sustainable. These properties make the material of the present invention an environmentally friendly material with a completely biodegradable and sustainable character, highlighting it from other reinforced composite materials.

On the other hand, the biodegradable composite material of the present invention has advantages over synthetic composites typically used in terms of reducing biological risks associated with fiber use. For example, working with fiberglass, the most common material for the reinforcement of compounds, can cause irritation to the eyes, nose, throat and skin, in addition to the fact that fiberglass is classified as a possible carcinogen in humans. There are no associated risks associated with the use of the natural fiber of the present invention. In conclusion, its environmentally friendly nature, its incredible performance at the level of mechanical and physical properties, its non-existent biological risk during handling, as well as its attractive visual appearance, make the composite material of the present invention a competitive material to be Used in different industrial sectors.

The manufacturing method of the present invention provides exceptional mechanical properties to the biodegradable natural composite material by the strong coupling achieved between the Manicaría saccifera fiber and the polylactic acid resin. In this way, the specific manufacturing method for this composite material improves the micromechanical interfacial adhesion between the matrix and the fiber, which provides exceptional mechanical properties.

As shown in Figure 4, the manufacturing method is divided into three main stages: A. Preparation of the Manicaría saccifera fiber, B. Preparation of the polylactic acid and C. Hot compression molding.

A. The first stage of the manufacturing method consists in the preparation of the fiber of the Manicaría saccifera palm to be used as a reinforcement in the biodegradable natural compound. In turn, this first stage is divided into three fundamental parts: cutting, chemical treatment and preforming. First, during the fiber cutting, the bract of Manicaría saccifera (5) emerges; that is, the tip and base of the bract are cut by means of a scissor or shear. These parts of the bract are discarded and not used during the manufacture of the compound because their properties are not suitable for use as reinforcement in the composite. Then, because the bract is in the form of a bag and to take advantage of its entire cross section, a longitudinal cut is made to open it in its maximum width in the form of a fabric.Afterwards, a chemical treatment is applied to the Manicaria saccifera fabric to potentiate its coupling with the matrix of Polylactic acid and increase the mechanical properties of the compound. The objective of this chemical treatment is to eliminate impurities, fats and lignin accumulated on the surface of the fibers that prevent a correct union between the fiber and the matrix and thus improve the wettability of the resin in the fibers. For this chemical treatment a bath of sodium hydroxide solution (NaOH) should be prepared in a concentration of 2% to 15% by weight and a bath of acetic acid solution (C ₂ H ₄ 0 ₂ ) in concentration of 0.5% at 5% by weight. Then, the fiber is immersed in the sodium hydroxide bath for a time between 10 and 180 minutes. It must be ensured that the fiber is fully submerged in the solution and continuous agitation of the system that allows surface substances to be removed. The ratio between the amount of fiber and the amount of solution should be between 0.02 and 0.2 grams of fiber per milliliter of solution. Once the washing time is completed, the fiber is removed from the bath and washed with plenty of water to remove the sodium hydroxide. The temperature of the wash water may be at a temperature between 15 ° C and 80 ° C. The fiber is neutralized by immersing it in the acetic acid solution bath for a time between 0.2 and 5 minutes. Ensure that the fiber is fully submerged in the solution and continuous agitation of the system. The ratio between the amount of fiber and the amount of solution should be between 0.02 and 0.2 grams of fiber per milliliter of solution. Once the neutralization time is completed, the fiber is removed from the bath and the fiber is removed from the bath and washed with plenty of water to remove acetic acid. After the neutralization process, the pH of the fiber should be around 7. Finally, the fiber is taken to an oven at a temperature between 90 ° C and 1 10 ° C for a time between 10 and 180 min for drying until it reaches a relative humidity of less than 1%. Likewise, the fiber is cut to its final dimensions of use depending on the part that will be manufactured and the mold that will be used. It is preformed by compression at a pressure between 0.1 and 0.5 MPa and a temperature between 60 ° C and 1 10 ° C to be used as reinforcement in the composite material; This process can be done during the fiber drying process. Optionally, at the end of this stage a fabric dyeing process of Manicaria saccifera can be carried out in order to obtain fiber of different colors In parallel, the polymeric polylactic acid resin is prepared to be used as a matrix of the biodegradable natural compound. This stage comprises four parts: drying, extrusion, heat treatment and preforming. In the first instance, the PLA pellets (4) are subjected to a drying process to remove moisture in an oven at a temperature between 90 ° C and 10 ° C until reaching a relative humidity of less than 0.1% to prevent possible degradation by hydrolysis of the material. Then using an extruder with a temperature profile between 180 ° C and 200 ° C, the PLA pellets are laminated into sheets (3) of thickness between 0.2 and 1.5 mm. At this stage of the process, during extrusion, additives or additional components can be added in a proportion between 0.1% and 15%. UV stabilizers, antistatic agents, flame retardants, among others, can be added to the mixture to improve the properties of the composite material.

Subsequently, an annealing heat treatment is performed on the PLA sheets in an oven at a temperature between 90 ° C and 140 ° C for a time between 30 and 120 minutes. This heat treatment allows recovering the ductility of the PLA sheets for proper handling during the manufacture of the composite material. Also during this heat treatment the remaining moisture is removed from the PLA sheets. PLA sheets are preformed by compression at a pressure between 0.1 and 0.5 MPa and a temperature between 60 ° C and 10 ° C to be used in the composite material; This process can be performed during the heat treatment process of PLA sheets. Finally, hot compression molding of the final piece of the biodegradable natural composite of PLA reinforced with fiber of Manicaria saccifera is performed. This stage comprises four parts: preheating, layer stacking, molding and final finishing. First, the mold of the piece must be preheated until it reaches a temperature between 150 ° C and 210 ° C. The mold must be prepared with non-stick material to ensure the release of the final piece. Then, alternate stacking of PLA sheets with layers of Manicaria saccifera fiber should be performed. The number of stacked layers is selected according to the desired thickness and according to the mechanical and physical requirements in proportions of fiber to resin ratio between 10% and 95% by weight. Likewise, the laminate configuration and the orientation of the Manicaria sacciferase layers are distributed according to the mechanical and physical specifications of the final piece. Subsequently, the mold is closed and the hot compression molding process is carried out at a constant temperature between 150 ° C and 210 ° C throughout the cycle. Initially, during the molding a venting process is carried out to dislodge the trapped air between the different layers of the laminate. This process consists of performing compression cycles at low pressure, between 0.1 and 0.8 MPa, for times between 3 and 15 seconds and subsequent pressure release. These cycles are repeated constantly for total vent time between 1 and 5 minutes. After removing the trapped air between layers, the material is compressed at a pressure between 0.5 and 3 MPa for a time between 2 and 60 minutes. Once the compression time is completed, the mold is cooled keeping the pressure constant until it reaches a temperature below 45 ° C; temperature at which the pressure is removed, open the mold and unmold the final piece. Finally, we proceed to finish the piece by removing flanges. This manufacturing method provides the biodegradable natural composite material of the present invention with exceptional mechanical properties that are explained at the micromechanical level. First, to demonstrate the effect of the chemical treatment on the morphology of the fiber surface, a microscopic analysis of the longitudinal section of both the fiber to which the preparation proposed in this invention is applied and the treated fiber is made by technique. of electron microscopy (SEM). The micrographs of the fibers with and without treatment are shown in Figure 5. It was observed that, the untreated fiber (Figures 5a and 5b), has an epidermis of lignin, impurities and waxes on the surface of the fiber. The presence of lignin and waxes in the tissue decreases the bond between the fiber and the polymer and reduces moisture. On the contrary, the results of the fiber after the application of the chemical treatment show an important change in the morphology of the fiber. As Figure 5c is observed, the treatment applied to the fiber of Manicaria saccifera proved to be effective in eliminating most of the substances that cover the surface of the fabric, improving its wettability. After treatment, it is easier to identify that Manicaria saccifera fiber is a fibrous material, and is made up of crosslinked fibers. In effect, the fabric shows a particular fabric design. The tissue is obtained by bifurcation, crossing and fiber overlap. At higher magnification (Figure 5d), it is observed that the treatment leads to a cleaner fiber surface. After partial removal of lignin, hemicellulose, waxes, and impurities, the fiber diameter is reduced. In this way, the aspect ratio increases, the effective surface area of the fiber increases, resulting in improved adhesion with the matrix. As shown in Figure 5e, the chemical treatment also allowed to increase the surface roughness and the amount of cellulose exposed on the fiber, which resulted in better interfacial adhesion and greater load transfer capacity. In addition, uniformly distributed globular protrusions were observed on the fiber surface. In terms of the mechanical behavior of the composite material, these globular protrusions play an important role in improving the mechanical interlocking with the PLA resin. While they came off Some globular protrusions of their place after treatment leaving craters (Figure 5f), these improve the penetration of the matrix into the fiber during the manufacture of composite materials.

Likewise, to analyze and identify the micromechanical effects of the manufacturing method presented in the present invention on the mechanical behavior of the biodegradable natural compound, an SEM fracture analysis was performed both on a sheet manufactured following the procedure of the present invention and in a composite material with untreated fiber. Figure 6 shows micrographs of the fracture surface of tension probes of both untreated fiber composite material (figure 6a-b) and the compound manufactured with the present method (figure 6c-f) at different magnification levels. Although the main failure mechanisms identified in both materials were: fiber fracture, pull-out and matrix breakage; Unlike the compound manufactured with the present method, pull-out is much more frequent in the untreated fiber composite material, indicating low fiber-matrix adhesion. Figure 6b shows that the fibers are not well impregnated by the resin, to the extent that the morphology of the fiber constituted by an epidermis, cell wall, and lumen can be clearly seen. In turn, an important gap between fiber and PLA is seen as another sign of low adherence between them. In contrast, Figure 6c shows an overview of the compound manufactured by the method of the present invention in which the fiber fracture is predominant as a failure mechanism, indicating strong adhesion between the fiber and the matrix. The fibers are well impregnated by the PLA matrix. The cavities that constitute the microstructure of the fiber have been filled by the matrix (Figure 6d). The gaps between the fiber and the PLA matrix were reduced, and the geometry of the fiber is marked on the resin after fiber separation (Figure 6e). In fact, the globular protrusions identified on the fiber surface are marked on the resin (Figure 6f). Not only the geometry of the globular protrusions are marked in the matrix but also some are attached to the matrix, indicating the good mechanical interlocking between the fiber and the PLA matrix. This analysis confirms the reasons for the improved mechanical properties of the biodegradable natural composite material manufactured by the method of the present invention compared to the untreated fiber composite.

EXAMPLES

Example 1 :

According to the invention, samples of the biodegradable composite material with a fiber-to-matrix ratio of 60% by weight were manufactured. Subsequently, its mechanical properties were characterized by showing exceptions and unexpected properties compared to other similar natural compounds and even competitive properties with synthetic fiberglass compounds.

Mechanical characterization

Material samples were mechanically characterized by stress, flexion and impact tests according to the following procedures:

Tension Test: Tension tests were carried out according to ASTM D3039 in an Instron 3367 universal testing machine. Rectangular geometry specimens were tested at a speed of 2 mm / min and a calibrated length of 50 mm. To record the deformation during the test, an extensometer device was used.

Flexural test: Flexural tests were performed in accordance with ASTM D790 using the Instron 3367 universal testing machine. The samples were loaded by three-point flexion with an aspect ratio of 16: 1. Impact test: Impact resistance tests were performed with Izod samples without notch in accordance with ASTM D 256-06 using a TMI impact test machine, model 43-1.

Due to the particular method of manufacturing the compound and the unique structure of the fiber reinforced PLA compound extracted from the bract of Manicaria saccifera, the material of the present invention exhibits superior mechanical properties to other compounds reinforced with natural fibers and polyamide. lactic as shown in figure 7 for tensile strength, figure 8 for flexural strength and figure 9 for impact resistance.

When reviewing the results of the mechanical tests performed and the comparisons presented in the figures, it can be concluded that the material presented in this invention exhibits typical tensile strength properties of 123.36 MPa, flexural strength of 209.68MPa and resistance to impact of 36.94 kJ / m ² that make it mechanically superior to similar compounds. Although some natural compounds have some high mechanical properties, the Manicaria saccifera and PLA compound produced by the method of the present invention has unexpected higher values in all three properties (tensile strength, flexion and impact) simultaneously.

Additionally, Figure 10 shows the comparison of the stress-strain stress and flexion curves of the PLA composite material reinforced with natural fibers of Manicaria sacifera using the manufacturing method of the present invention with the same compound of PLA and Manicaria sacifera manufactured without treatment and using traditional manufacturing methods. Likewise, figure 10 shows the curve for the polymer matrix of PLA without reinforcement. The results of these mechanical tests demonstrate that the compound of the present invention obtained By the specific method described above, it provides exceptional and unexpected properties to the material compared to the same compound manufactured with traditional methods. It can be seen that the specific manufacturing method of this invention considerably improves the mechanical strengths of the biodegradable compound both at tension and at flexion; showing improvements of 85% in its tensile strength and 59% in its flexural strength.

On the other hand, Figure 1 shows the comparison of the specific tensile and flexural mechanical strengths of the biodegradable natural compound of the present invention with traditional structural fiberglass compounds. The analysis of this comparative graph allows us to observe how the natural compound of the present invention has specific competitive properties with fiberglass structural compounds with polyester and vinyl ester resins traditionally used in various applications of different industrial sectors. In the graph it can be seen that the specific mechanical properties of the compound referred to in the present invention have similar or superior values to fiberglass compounds, only being surpassed by a compound reinforced with high-performance roving fabric. This comparison allows observing the exceptional mechanical properties achieved by the fiber reinforced PLA compound of Manicaría saccifera, which, while maintaining a completely biodegradable and sustainable character, reaches specific mechanical resistance values at the level of traditional synthetic compounds.

Example 2:

According to the invention, samples of the biodegradable composite material with a fiber-to-matrix ratio of 70% by weight were manufactured. Subsequently, their acoustic properties were characterized by showing exceptional and unexpected properties compared to other similar natural compounds. An absorption coefficient was observed acoustics for the biodegradable compound superior to materials typically used for acoustic insulation such as expanded polystyrene at low frequencies (125 Hz and 250 Hz).

Acoustic characterization

Samples of the material were acoustically characterized according to the ASTM 1050 technical standard by means of an impedance tube to determine the coefficient of sound absorption of the material at different frequencies. Acoustic absorption coefficient measurements were made at frequencies of 125 Hz, 250 Hz, 500 Hz, 1 kHz and 2 kHz.

The fiber reinforced PLA compound of Manicaria saccifera showed very competitive acoustic properties in relation to other materials. Displaying an acoustic absorption coefficient of 0.45 on average for the measured frequency range; with a maximum of 0.49 for the frequency of 250 Hz.

A comparative graph of the acoustic absorption coefficients at different frequencies (125 Hz, 250 Hz, 500 Hz, 1 kHz and 2 kHz.) Of the biodegradable natural compound of the present invention and expanded polystyrene, non-material, is shown in Figure 12. biodegradable or recyclable typically used for sound insulation applications. Unexpected and superior behavior can be observed in the sound absorption capacity of the material of the present invention at low frequencies of 125 Hz and 250 Hz compared to expanded polystyrene. Higher sound absorption coefficients were measured at 27% and 25% for these frequencies respectively. This particular behavior, in which the acoustic absorption coefficient is exceptional at low frequencies is inverse to the behavior typically observed in usual acoustic insulation materials such as expanded polystyrene, in which better performance is observed at high frequencies. Consequently, the composite material Biodegradable of the present invention, is shown as a material with various sound insulation applications.

Claims

one . Method for manufacturing a composite material, the method characterized by comprising the steps of:  a) Prepare the natural fiber of Manicaria saccifera palm by means of the following sub-stages:  a1) cut and detach the bracts of Manicaria saccifera by means of scissors or shears;  a2) cut longitudinally the bracts collected from Manicaria saccifera to open them at its maximum width in the form of a cloth;  a3) prepare a bath of sodium hydroxide solution in a concentration of 2% to 15%, and submerge the natural fiber obtained in step a2) for a time between 10 and 180 minutes; where the fiber is completely submerged in the solution bath and continuous agitation of the system is carried out; and where the ratio between the amount of fiber and the amount of solution is between 0.02 and 0.2 grams of fiber per milliliter of solution;  a4) remove the fiber treated in step a3) and wash with plenty of water to remove sodium hydroxide;  a5) prepare an acetic acid solution bath in concentration of 0.5% to 5% by weight and submerge the natural fiber obtained in step a4) for a time between 0.2 and 5 minutes; where the fiber is completely submerged in the solution bath and continuous agitation of the system is carried out; and where the ratio between the amount of fiber and the amount of solution must be between 0.02 and 0.2 grams of fiber per milliliter of solution;  a6) remove the fiber treated in step a5) and wash with plenty of water to remove acetic acid;  a7) drying the material obtained from step a6) in an oven at a temperature between 90 ° C and 10 ° C for 10 to 180 minutes; a8) preform the material by compression at a pressure between 0.1 and 0.5 MPa and temperature between 60 ° C and 10 ° C; b) Parallel to step a), prepare a polylactic acid (PLA) resin using the following sub-stages: b1) drying PLA pellets in an oven at a temperature between 90 ^and C and 1 10 ° C to reach a relative humidity below 0.1%;  b2) extrusion laminating the PLA at a temperature between 180 ° C and 200 ° C until sheets with a thickness between 0.2 and 1.5 mm are obtained;  b3) heat treat the PLA sheets obtained in step b2) in an oven at a temperature between 90 ° C and 140 ° C for a time between 30 and 120 minutes;  b4) preform the PLA sheets by compression at a pressure between 0.1 and 0.5 MPa and temperature between 60 ° C and 10 ° C;  c) hot compression molding the final piece of the natural biodegradable PLA compound reinforced with Manicaria saccifera fiber by means of the following supercaps:  d) preheat a mold according to the shape of the final material that is desired to obtain until reaching a temperature between 150 ° C and 210 ° C;  c2) alternately stack the PLA sheets with layers of Manicaria saccifera fiber, where the ratio of fiber to resin is between 10% and 95% by weight;  c3) close the mold and perform hot compression at a constant temperature between 150 ° C and 210 ° C, where during the molding a venting process is carried out simultaneously that dislodges the trapped air between the different layers of the laminate;  c4) compress the material at a pressure between 0.5 and 3 MPa for a time between 2 and 60 minutes;  c5) cool the mold to a constant pressure until it reaches a temperature below 45 ° C c6) remove pressure, unmold the material and finish the piece according to the desired shape of the final piece. 2. The method of manufacturing a composite material according to claim 1, wherein the venting process comprises the following steps:  i) perform pressure compression cycles between 0.1 and 0.8 MPa for times between 3 and 15 seconds; Y  ii) relieve system pressure;  where processes i) and ii) are repeated repeatedly for total venting time between 1 and 5 minutes. 3. The method of manufacturing a composite material according to claim 1, wherein the mold of step c1 is non-stick. 4. The method for manufacturing a composite material according to claim 1, the method which additionally comprises after step a6, subjecting the fiber of Manicaria saccifera to a dyeing process to change its color. 5. The method for manufacturing a composite material according to claim 1, the method which additionally comprises during step b2 adding dyes, additives, UV stabilizers, antistatic agents or flame retardants to the polylactic acid. 6. A biodegradable natural composite material characterized in that it comprises:  a thermoplastic polymer resin consisting of a polymeric matrix of polylactic acid (PLA); Y Natural fiber sheets of the bract of the palm of Manicaríasaccifera, pretreated in a bath of sodium hydroxide solution in concentration of 2% to 15% and in a bath of acetic acid solution in concentration of 0.5% to 5% by weight . 7. The biodegradable natural composite material according to claim 6, further comprising dyes for the Manicaria saccifera fiber or the polylactic acid matrix in a proportion between 0.1% and 15%. 8. The biodegradable natural composite material according to claim 6, comprising additional components such as UV stabilizers, antistatic agents, flame retardants, which improve the properties of the composite material.