NL1010568C1 - Polyurethane composite. - Google Patents

Description

- 1 -

POLYURETHANE COMPOSITE

The invention relates to a composite comprising a network of strong fibers, with a strength of at least 6 dN / tex, a modulus of at least 130 dN / tex and a breaking energy of at least 8 J / g in a thermoplastic polyurethane 10 matrix. Such a composite is suitable for providing protection against ballistic projectiles, especially in anti-ballistic molded parts such as helmets, panels and vests.

Such a composite is known from EP-A-15 0645415. EP-A-0645415 describes a composite, comprising a network of strong fibers with a tensile strength of at least 6.18 dN / tex, a modulus of at least 132.45 dN / tex and a fracture energy of at least 8 J / g in a thermoplastic polyurethane matrix.

A drawback of such a composite is that the deformation (hereinafter referred to as the "trauma") is relatively large behind the location of a projectile impact, so that a person protected by the antiballistic molded part runs the risk of being injured by this high deformation.

The object of the invention is to provide a composite with which moldings can be manufactured that do not, or to a lesser extent, exhibit this drawback.

This object is achieved according to the invention in that the matrix contains an amorphous polyurethane at room temperature.

$ 8 '(u 0 5 6 8 - 2 -

A "composite" is here understood to mean a composition of at least two prepregs. In general, several prepregs are consolidated in a composite, the adjacent prepregs making an angle of preferably approximately 90 ° with each other.

A "prepreg" is understood to mean a network of fibers held together by a matrix.

By "fibers" here is meant 10 stretched objects, the length of which is much greater than the width and thickness. Fibers include continuous mono and multifilaments, as well as discontinuous filaments such as staple or chopped fibers.

A "network" of fibers is understood to mean a composition of a plurality of fibers, in which the composition has a specific configuration. Examples of configurations of the compositions are a felt, a knit, or a fabric. Preferred is a unidirectional network, in which the fibers are mainly parallel to a common fiber direction.

"Strong fibers" in this invention are fibers with a strength of at least 6 dN / tex, a modulus of at least 130 dN / tex and a beech energy of at least 8 J / g. Preferred are strong fibers, fibers with a strength of at least 10 dN / tex, a modulus of at least 200 dN / tex and a beech energy of at least 20 J / g. More preferred are fibers with a strength of at least 16 dN / tex, a modulus of at least 400 dN / tex and a beech energy of at least 27 J / g. Most preferred are fibers with a strength of at least 28 dN / tex, a modulus of at least 1200 dN / tex and a beech energy of at least 40 J / g.

pl 0 1 0 5 6 8 - 3 -

Suitable strong fibers are fibers of its glass, carbon, aramid, silicon carbide, and / or a stretched polymer, such as, for example, stretched ultra-high molecular weight polyethylene, and / or combinations thereof. The fiber material preferably consists of ultra-high molecular weight polyethylene.

Ultra high molecular polyethylene is understood to mean polyethylene having a weight average molecular weight of at least 500,000 kg / kmol. Preferably the molecular weight is more than 2,000,000 kg / kmol.

According to the invention, the fibers are embedded in a thermoplastic polyurethane matrix, which is amorphous at room temperature. Amorphous polyurethanes can be obtained by an obvious choice for those skilled in the art from the polyols and diisocyanates that make up the polyurethane, as described, inter alia, in Polymer, 1991, Volume 32, p. 343-352.

The modulus of the polyurethane can be chosen within wide limits, depending on the stiffness requirements to be imposed on the composite. Preferably, the modulus of the polyurethane is at least 5 Mpa. This achieves the result that a molded part made from the composite according to the invention does not contain delaminations between two successive composite layers when the part is demoulded after pressing at a temperature lower than 100 ° C. It has been found that moldings made from a composite whose polyurethane modulus is less than 5 MPa after mold demoulding may contain delaminations between two successive composite layers.

Preferably, the matrix contains a thermoplastic polyurethane, the modulus of which is at least 8 MPa. This ensures that the p1 0 1 0 5 6 8-4 molded part which has been demoulded at the temperature at which it has been pressed does not contain any delaminations.

In the polyurethane of the matrix, surfactants can be used, which are used as a stabilizer for a polyurethane dispersion from which the composite can be manufactured. Preferably, the surfactant content in the polyurethane matrix is less than 0.01% by weight. This ensures that aging of the matrix 10 hardly takes place under the influence of light or heat. Matrices in which a content of more than 0.01% by weight of a surfactant is present, exhibit accelerated aging behavior.

The invention also relates to a prepreg containing a network of strong fibers in a thermoplastic polyurethane matrix, with strong fibers and a polyurethane matrix according to the invention. A further advantage of the invention is that the prepreg contains fewer gels than 20 when it contains a crystalline polyurethane.

Composites according to the invention can be helmets, panels and vests. The composite according to the invention is preferably a helmet. The invention also relates to a helmet, comprising a first composite according to the invention.

Where necessary, the stiffness of the helmet according to the invention can be increased by providing the helmet on the outside with a layer containing a second composite. Such second composites can consist of combinations of known fibers such as glass, polyethylene, carbon, aramid and nylon with polymeric matrices.

Preferably, such a second composite consists of a glass fiber in a polymer matrix.

35 The use of glass fibers ensures that the pi o 1 05 6 8 - 5 helmet is easy to paint.

The polymeric matrix preferably consists of a thermosetting polymer. This achieves that the helmet, the polyurethane of which has a relatively low modulus, can also be released at pressing temperature. Thermosetting matrices can be phenol, phenol / polyvinyl butyral, epoxy and vinyl ester.

Preferably, the thermosetting matrix is a vinyl ester. Hereby a good adhesion with the polyethylene fibers of the helmet is achieved.

The invention also relates to a method for preparing the composite according to the invention and in particular to preparing a prepreg from which the composite is built. Generally, prepregs are prepared by wetting fibers with a solution, or a dispersion of a matrix material, or with monomers of a matrix material in a solvent or dispersant. The fibers can also be wetted with a melt of the matrix material 20. The wet fibers are generally applied to a support material, after which they are stripped on a drying line, if necessary, in an oven, and then cooled. Such a method is known from EP-A-25 0645415. In EP-A-0645415, strong polyethylene fibers are wetted with an aqueous solution in which an aliphatic diisocyanate monomer and a polyol monomer are dispersed. During the evaporation of the water, the monomers polymerize to form the polyurethane.

A drawback of such a method is that the polymerization and evaporation take a relatively long time. EP-A-0645415 describes that this requires a drying line of 10 m in length.

The aim of the invention is to provide a p1 0 1 0 5 6 8 - 6 method in which a considerably shorter drying line suffices.

This object is achieved according to the invention in that strong fibers are wetted with an aqueous polyurethane dispersion and the polyurethane is amorphous at room temperature.

Surprisingly, it has been found that when using an aqueous dispersion of a polyurethane which is amorphous at room temperature, a drying line of only two meters would suffice at a production speed of about 15 m / min. A further advantage of the method according to the invention is that there are no or hardly any gels in the prepreg manufactured according to this method. When the fibers are wetted with the solution of monomers known from EP-A-0645415, in a drying line with a length of 2 m no prepreg could be obtained with an economically somewhat acceptable production speed, and there were in the known manner prepreg manufactured a large number of gels. A "gel" is understood to mean a local thickening of the matrix material on the prepreg. Such thickenings lead to undesirable irregularities in the prepreg and the composite made from it.

The composite according to the invention is manufactured by stacking two or more prepregs, the angle between the fibers of two adjacent prepregs being substantially greater than 0 °. Preferably, the angle between two adjacent prepregs 30 is about 90 °. The stack of prepregs is then consolidated by pressing them under elevated temperature. Composites containing two or four prepregs can be stacked and processed into a flexible object, such as an anti-ballistic vest. In that case, the modulus of the

β1 0 10 5 6 B

- 7 - polyurethane no specific requirements.

It is also possible to form a hard object from the prepregs by pressing several layers into a composite in a mold. Pressing generally takes place at a temperature of between 100 and 130 ° C. In the case where a hard object is pressed, the polyurethane preferably has a modulus of at least 5 MPa. This ensures that the composite can be released from the mold at a temperature of at least 100 ° C

without delamination during demoulding. This has the advantage that the mold does not have to be cooled below 100 ° C in order to de-mold the molded part and then have to be reheated before pressing the next molded part.

Modulus is here understood to mean the secant modulus measured on a film of the polyurethane at an elongation of 100%.

Preferably, the polyurethane has a modulus of at least 8 MPa. This achieves that the molded part can be demoulded at the pressing temperature, so that the mold does not have to be cooled at all, which is very advantageous both energetically and economically. The condition here is that there is good adhesion between the polyurethane and the matrix. This is achieved by the features of the method according to the invention.

Since the mass of the mold with which a helmet is manufactured is relatively large due to the voluminous core, it takes a relatively large amount of time and energy to heat and cool such a mold for each molded part. The advantages of the features of the invention are therefore particularly appreciated in the manufacture of a helmet. As a result, relatively little energy is required for the manufacture of a helmet according to the invention and the cycle time during pressing is relatively short.

In the manufacture of polyurethane dispersions, surfactants are often used to stabilize the dispersion. Preferably, the method of the invention uses a polyurethane dispersion containing less than 0.01% by weight of a surfactant.

This ensures that the drying can proceed even faster and that during drying no bubbles are formed between the carrier material and the prepreg formed.

The invention will be further elucidated by means of the examples without being limited thereto.

The 'trauma' effect is determined and characterized by the bulge of the object behind the location of the impact of a projectile. The trauma was measured according to standard EN ISO 14876-3. The 20 plastiline used is Caran D'ache type "Modella

Essai, CDA 259.001 ". The standard prescribes heating the plastiline to a temperature at which a ball with a diameter of 63.5 mm and a weight of 1043 grams gives an indentation depth of 20 ± 2 mm at a drop height of 200 cm. In in the comparative tests described below, the plastilin was used at a constant temperature of 20 + 2 ° C. At this temperature, the indentation of the said bullet at a fall from a height of 200 cm is 17-19 mm.

30 »1010568 - 9 -

Examples

Example I

A network of 52 g / m2 unidirectional 5 oriented yarn Dyneema SK76 with a modulus of 1180 cN / dTex, a strength of 36 cN / dTex and a titer of 1760 dTex is impregnated with an aqueous dispersion of polyurethane "Witcoflex 130 Matt" (Baxenden Chemicals, 100% Tensile modulus = 5 MPa). The aqueous dispersion contains 28% solids. The impregnated fleece is dried on a drying bridge of 2 meters in length and a temperature of 100-103 ° C at a transport speed of 6 m / min. At higher transport speeds, the residual volatile content rises above 1%. The prepreg thus obtained has a surface weight of 70 gr / m2 and contains 25.7% matrix. By 0/90/0/90 ° stacking of 4 layers of impregnated prepreg, a laminate of 280 g / m2 is produced with a calender. Some of the laminates 20 thus obtained were pressed for 30 minutes at 10 bar and 128 ° C into a composite panel. The pressed panels are demoulded at 100 ° C and ballistic tested against various threats. The results of these tests are listed in Table 1a.

25 label la:

Ballistic evaluation UD laminate based on Witcoflex 130 PUR matrix.

p 1 ij 1 0 5 6 3 - 10 -

Threat number of surface area T "V5Ö Energy lamina weight [kg / m2] [m / s absorption ten] [j / kg / m2] 17 grain 25 TTo 617 29.8

FSP

9 mm ÏÖ 2.8 '388 216 parabellum .357 GECO 18 572 “474 222 7.62x51 NB 75 2ÏT2 833 Ï55

Then 10 layer pressed composites based on UD with Witcoflex 130 Matt (25.7% matrix) were bombarded with 5 bullets 9 mm parabellum at a speed of ± 340 m / s as well as with 5 bullets 7.62 Nato Ball at a speed of + 800 m / s on a plastiline backing (Caran d'Ache). The velocity of the bullets and the trauma caused was measured and the average is shown in Table 1b.

Comparative Experiment 1

In an identical manner as under example I 15, 10 layer pressed panels based on UD were produced with Polyurethane Dispercoll U42 (24.8% matrix) and bombarded in an identical manner as described above.

The results of this are shown in Table 1b. Dispercoll U42 is a semi-crystalline matrix.

20

p1 0 1 0 5 δ S

- 11 - label lb:

Trauma from UD-Witcomatt 130 versus UD-Dispercoll U42 measurements

Threat Matrix number surface area V Trauma layers weight [m / s] [mm] [kg / m2] 9 mm Witcomatt ~ ÏÖ 2.8 341 22 parabellum 130 9 mm Dispercol 10 2.8 339 27 parabellum 1 U42 7.62 nato Witcomatt 75 2Ï2 794 28 ball 130 7.62 nato Dispercol ~ 75 21.1 796 34 ball 1 U42 5 This shows that a polyurethane matrix based on an amorphous polyurethane at room temperature produces less trauma than a polyurethane based on a semi-crystalline polyurethane.

Example II

The impregnation of the network was carried out according to example I with the difference that as the aqueous polyurethane dispersion white cobond 736 was used (Baxenden Chemicals, 100% modulus = 8 MPa).

Witcobond 736 has a solids content of 40%. The transport speed of the impregnated web on the drying line is 15 m / min, the residual volatile content in the obtained prepreg being less than 1%. The prepreg has a surface weight of 68 g / m3 and 20 contains 22.4% matrix. By 0/90/0/90 ° stacking of 4 φ \ 010568 - 12 - layers of prepreg, a laminate of 272 g / m2 is produced using a calender. 10 layers of the resulting laminate were pressed into a composite panel at 10 bar and 128 ° C for 30 minutes. The panels 5 were demoulded at 100 ° C. The pressed panels have been ballistic tested against various threats.

The results are shown in Table 2.

labs L. 2 · 10 Ballistic evaluation UD laminate based on Witcobond 736 PUR matrix.

Threat number of surface V50 Energy layers weight [kg / m2} [m / s] absorption [J / kg / m2] 9 mm ÏÖ 2/7 396 234 parabellum .357 GECÖ 18 572 465 225

At an average speed of 340 m / s, 9 mm 15 parabellum bullets cause trauma of 21 mm.

Example III

The impregnation of the network was carried out according to example I with the difference that as polyurethane dispersion Witcobond 246-41 (Baxenden

Chemicals, 100% Tensile modulus = 6 MPa) has been used. Witcobond 246-41 has a solids content of 40%.

The transport speed of the impregnated network over the drying bridge is 15 m / min, the residual volatile content in the prepreg being less than 1%. The prepreg obtained p 10 7 6 8-13 has a surface weight of 65 g / m2 and therefore contains 20% matrix. By 0/90/0/90 ° stacking of 4 layers of prepreg, a laminate of 260 g / m2 is produced using a calender. The laminate obtained was pressed by 30 minutes at 10 bar and at 128 ° C into a composite panel. The panels were demoulded at 100 ° C. The pressed panels have been ballistic tested against 9 mm parabellum bullets. The results are shown in Table 3.

10

Table 3:

Ballistic evaluation UD laminate based on Witcobond 246-41 PUR matrix.

Threat number surface area V5Ö Energy layers weight [kg / m2} [m / s] absorption [J / kg / m2] 9 mm ÏÖ 2.7 419 269 parabellum 15

At an average speed of 337 m / s, 9 mm parabellum bullets cause trauma of 22 mm.

Example IV

18 layers of laminate of Example II were pressed into a composite panel according to Example II, except that the panel was pressed at 128 ° C for 10 minutes, and the mold was opened at this temperature. The ballistic performance against .357 GECO is 25. The performance is the same as that of a panel pre-demoulded to 100eC cooled. The heat removal of the pressed panels on the basis of UD \ Witcobond 736 gives no delamination and a comparable stiffness and ballistic performance compared to panels cooled to 100 ° C before unloading.

The ballistic performance of these plates is shown in Table 4.

Table 4: 10 Hot-formed UD laminate based on Witcoflex 736 PUR matrix.

Threat number of surface V50 Energy layers weight [kg / mJ} [m / s] absorption [J / kg / mJ] .357 GECO 18 ΓΓ2 462 224

The UD laminate of Example II was used for pressing helmets. For the deep drawing of the helmet, 22 squares of 45 x 45 cm UD laminate were used, in the crown of the helmet b 20 circles (diameter 30 cm) UD laminate were added. The helmets were pressed for 20 minutes at 128 ° C and a pressure of 225 tons, after which the mold was opened. The weight of the helmet is 907 grams. The helmet showed no delaminations. The ballistic 25 performance of the helmet has been tested against 17 grain FSP according to Stanag 2920. The V50 is 677 m / s.

p1010568 - 15 -

Example VI

Example V has been copied with the difference that for the finish of the helmet 1 layer of glass \ vinyl ester has been added to the inside and outside of the helmet. The glass \ vinyl ester used has a surface weight of 270 g / m2 and a vinyl ester content of 50%. The helmet of example VI has a smoother surface and higher stiffness than the helmet of example V and is more paintable. 10 The adhesion between the UD laminate and glass \ vinyl ester fabric is good; no delaminations were visible. Surprisingly, the glass vinyl ester composite has no negative effect on the V50 against 17 grain FSP.

Example VII

Example VI has been copied with the difference that instead of glass \ vinyl ester, aramid fabric \ vinyl ester was used. The aramid fabric \ vinyl ester used has a surface weight of 20 285 g / m2 and a vinyl ester content of 20%. The helmet of example VII has a smoother surface and higher stiffness than the helmet of example V and is moreover paintable. The helmet of Example VII has a lower stiffness than the helmet of Example VI and the paint adhesion is less than the helmet of Example VI. Addition of the used aramid \ vinyl ester fabric hardly has a positive effect on the V50 against 17 grain FSP.

p 1 0 1 0 5 6 8

Claims (12)

Composite containing a network of parallel 5 strong fibers, with a strength of at least 6 dN / tex and a modulus of at least 130 dN / tex and a breaking energy of at least 8 J / g in a thermoplastic polyurethane matrix, with the characterized in that the matrix contains an amorphous polyurethane at room temperature. Composite according to claim 1, characterized in that the modulus of the polyurethane is at least 5 MPa. Composite according to claim 1 or 2, characterized in that the modulus of the polyurethane is at least 8 MPa. Composite according to any one of claims 1-3, characterized in that the composite contains less than 0.1% by weight of a surfactant. Prepreg containing at least two layers of a network of strong fibers in a thermoplastic polyurethane matrix, with fibers and matrix as described in any one of claims 1-4. 6. Helmet containing a first composite according to any one of claims 1-4. Helmet according to claim 6, wherein the helmet is provided on the outside with a second composite containing glass fibers in a thermosetting matrix. The helmet of claim 7, wherein the thermosetting matrix is a vinyl ester. 9. A process for preparing a prepreg according to claim 5, characterized in that strong fibers are wetted with an aqueous polyurethane dispersion and the polyurethane is amorphous at room temperature. Process according to claim 9, characterized in that the modulus of the polyurethane is at least 5 MPa. A method according to claim 9 or 10, characterized in that the composite contains less than 0.1% by weight of a surfactant. Use of the prepreg according to claim 5 for the manufacture of a helmet. 10 * »1 0 10 558