WO2004012934A1

WO2004012934A1 - Protective laminate structure

Info

Publication number: WO2004012934A1
Application number: PCT/US2003/024115
Authority: WO
Inventors: Mark Elden Schuchardt
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 2002-08-01
Filing date: 2003-07-31
Publication date: 2004-02-12
Anticipated expiration: 2005-02-01
Also published as: AU2003257116A1

Abstract

A protective laminate structure comprising a layer of a shear thickening material sandwiched between first and second flexible support layers, said first and second flexible support layers each being formed with multiple individual corresponding undulations, said undulations each having a base and a substantially flat top, said undulations arranged in a repeating pattern of offset rows wherein the laminate structure has at least three bending axes defined by adjoining rows of individual undulations.

Description

PROTECTIVE LAMINATE STRUCTURE

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to protective laminate structures. More particularly, the invention relates to laminate structures suitable for use in protective pads, protective apparel, or energy absorbing structures such as crash barriers.

2. Description of the Related Art

Protective garments such as flack jackets, motor cycle jackets and pants, protective workwear, and protective sports clothing and pads are well known. Such existing protective apparel often provides effective protection against physical shocks and impacts. However, existing apparel that provides satisfactory protection tends to be too bulky, heavy or rigid for comfortable wear by a user. In addition, such apparel is often structurally complicated making it expensive to produce.

U.S. Patent No. 5,599,290 discloses protective garments used to prevent bone fractures. The garments include arrays of flexible elastomeric polymer membrane enclosures filled with a shear-thickening material such as a dilatant material. The membrane enclosures are of a substantially flat rectangular shape that result in a pattern of bending along two perpendicular axes. In addition, the flat membrane shape adds little to the ability of the structure to absorb compressive shocks. PCT Patent Publication No. WO 00/69293 discloses an energy absorbing protective member having flexible thermoplastic envelopes filled with an energy absorbing material such as a dilatant material. The envelopes have a folded shape with an apex that helps to absorb energy when it is crushed. At the same time, the folded structure tends to be rigid making apparel utilizing such structures less flexible than is desirable. In order to try to add flexibility, WO 00/69293 discloses connecting numerous small folded envelope structures. However, such configurations are complicated and expensive to produce.

There is a need for a more flexible energy absorbing protective structure that can be mass produced at low cost. There is a further need for a protective structure that can be produced in large expanses on a high speed production line. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a portion of the laminate structure of the invention.

Figure 2 is a cross-sectional view of a portion of the laminate shown in Figure 1.

Figure 3 is a plan view of a portion of a laminate structure like that shown in Figure 1.

DETAILED DESCRIPTION

A laminate structure according to the invention is comprised of a layer of a sheer-thickening material sandwiched between two firm yet flexible support layers. The laminate structure of the invention has undulations that help to absorb sudden shocks, but the undulations are of a rounded shape and they are distributed in a pattern that greatly improves the flexibility of the laminate structure. Planer sections of the laminate structure of the invention can be incorporated into padding in protective garments such as flack jackets, motor cycle jackets and pants, protective workwear, and protective sports clothing. Sections of the laminate structure of the invention can also be incorporated into protective pads, such as padding used in sports equipment, or pads that can be inserted into receiving pockets of protective apparel. Alternatively, larger sections of the laminate structure of the invention can be incorporated into shock absorbing structures such as crash barriers. A preferred embodiment of the invention is shown in Figure 1. A laminate structure 10 is comprised of a layer of a shear-thickening material 14 sandwiched between two firm yet flexible support layers 12 and 16. The shear-thickening material is a material that is flexible under ordinary conditions, but that becomes substantially more stiff and rigid upon being subjected to a sudden mechanical stress or shock. Preferred sheer-thickening materials are dilatant compounds which are soft and flexible under ordinary conditions, but become much stiffer and more rigid when subjected to a sudden impact or shock. Upon being subjected to a sudden mechanical stress, a dilatant compound's ability to transmit shear forces almost instantaneously increases by a very significant amount. Polymers suitable for dilatant material include copolymers of styrene and acrylic acid or methylacrylic acid or their esters, and dimethyl siloxane hydroterminater polymers. One well known dilatent material is sold as a children's toy under the name Silly Putty®. The firm yet flexible support layers 12 and 16 may be comprised of a sheet structures that can hold a fixed shape but that are flexible as well. Preferably, the support layers 12 and 16 are comprised of a material offering good flexibility, and good impact and tear resistance, even at low temperatures when required. Examples of such materials may include thermoplastic polymer sheets, woven fabrics, nonwovens, papers, and metal foils. Where the laminate structures are to be used in apparel, it is preferred that the flexible support layers be permeable to moisture vapor.

Preferred materials for the support layers 12 and 16 are synthetic thermoplastic films and nonwoven sheets. Especially preferred materials are moisture vapor permeable thermoplastic elastomer films such as block polyether copolymers. In a preferred embodiment, the thermoplastic polymer resin is comprised primarily of a block polyether copolymer, such as a polyether ester copolymer, a polyether amide copolymer, a polyurethane copolymer, polyvinyl alcohol, or a combination thereof. Preferred copolyether ester block copolymers are segmented elastomers having soft polyether segments and hard polyester segments, as disclosed in U.S. Patent No. 4,739,012 (assigned to DuPont). Suitable polyether ester block copolymers are sold by DuPont under the name Hytrel®. Hytrel® is a registered trademark of DuPont. Suitable copolyether amide copolymers are copolyamides available under the name Pebax® from

Atochem Inc. of Glen Rock, New Jersey, USA. Pebax® is a registered trademark of Elf Atochem, S.A. of Paris, France. Suitable polyurethanes are thermoplastic urethanes available under the name Estane® from The B.F. Goodrich Company of Cleveland, Ohio, USA. h a more preferred embodiment, the flexible support layers 12 and 16 comprise sheets of copolyetherester elastomers having Shore D hardness of 40 to 50, and a thickness of 0.2 to 5 mm, and more preferably 0.5 to 1 mm. One particularly preferred copolyether ester elastomer that has been advantageously used in making the flexible support layers is DuPont' s Hytrel® Grade 5544 resin. According to the invention, the flexible support layers are formed with individual undulations that can be crushed to help absorb and distribute the energy from sudden shocks. The undulations are preferably individual rounded shapes and they are distributed in a pattern that greatly improves the overall flexibility of the laminate structure. In the preferred embodiment of the invention shown in Figures 1 and 2, the undulations are each substantially frustum shaped.

Alternatively, the base of each individual undulation could have an elliptical shape, another rounded shape, a square shape, or a polygonal shape. It is preferred that the largest cross-section of the base of each undulation be no more than 2.5 times the smallest cross-section of the base of the undulation. Preferably, each individual undulation 18 has a substantially flat top 20. In a preferred embodiment of the invention, each undulation 18 is formed in both the top flexible support layer 12 and the bottom flexible support layer 16, and each individual undulation has substantially the same shape. For example, each undulation could have frustum shape with a base diameter of 15 to 20 mm, a top diameter of 7 to 10 mm and a height of 8 to 12 mm. In the embodiment of the invention shown in Figure 2, the thickness of the shear-thickening material layer 14 is from 1 to 10 mm, and more preferably between 2 and 7 mm. According to the invention, the individual undulations are arranged in a pattern that provides at least three bending axes along which the laminate structure can naturally bend. More preferably, the pattern of individual undulations provides at least four bending axes, and even more preferably at least 5 or 6 bending axes. With the preferred offset pattern shown in Figure 3, there are six bending axes including a diagonal axis (a), a vertical a vertical axis (b), another diagonal axis (c), another diagonal axis (d), a horizontal axis (e), and another diagonal axis (f). This large number of bending axes makes for almost infinite flexing possibilities so as to provide an extraordinarily flexible laminate structure 10. The undulations in the flexible support layers can be made by a variety of means including hot or cold stamping and embossing, roll forming, thermo forming (with vacuum and/or pressure), hydro forming with pressurized fluid, injection molding, blow molding, or compression molding. The process applied depends upon the composition of the support layers, the form of the support layers (eg., nonwoven, film), and the desired production volume and production rate . With the preferred copolyether ester films described above, it has been found that the desired undulations can be economically formed by a cold stamping process. Where the support structure is a synthetic nonwoven sheet, the undulation pattern can be advantageously formed by the use of heated embossing rolls with complementary interlocking surfaces.

The shear-thickening layer 14 can be extruded directly onto either the bottom of the top flexible support layer 12 or the top of the bottom flexible support layer 16. Alternatively, the shear-thickening layer 14 can be prepared as a preformed film that is laid over one of the flexible layers. Where the shear- thickening layer is a dimethyl siloxane hydroterminater polymer, the layer readily conforms to the shape of the flexible layer on which the shear-thickening layer is extruded or laid down. Once the shear-thickening layer is in place, the remaining flexible layer can be added over the shear-thickening layer. Suction between the layers and surface tension are generally sufficient to hold the layers of the laminate structure in place. However, in order to assure that the layers remain in place, the flexible support layers 12 and 16 can be thermally welded to each other at desired points or they can be joined by other mechanical means, such as by sewing. Such joining techniques may also be used to break the laminate structure into sub-compartments so as to prevent migration of the shear-thickening layer 14.

Large expanses of the laminate structure of the invention can be economically produced at high production rates. The laminate structure of the invention exhibits excellent shock absorbing properties while at the same time being relatively lightweight and extraordinarily flexible. While the characteristics and advantages of the present invention have been set forth in the description above, together with details of the structure and function of the invention, the disclosure is illustrative only, and the full scope of the invention is as set forth in the claims that follow.

Claims

We claim:

1. A protective laminate structure comprising: a layer of a shear-thickening material sandwiched between first and second flexible support layers, said first and second flexible support layers each being formed with multiple individual corresponding undulations, said undulations each having a base and a substantially flat top, said undulations arranged in a repeating pattern of offset rows wherein the laminate structure has at least three bending axes defined by adjoining rows of individual undulations.