ES2626624T3 - Molded article with curved ballistic resistance - Google Patents

Abstract

A molded article with curved ballistic resistance comprising at least two sheets with ballistic resistance, wherein each sheet with ballistic resistance comprises a stack of at least 4 monolayers, each monolayer containing unidirectionally oriented reinforcing fibers with a tensile strength of between 3.5 and 4.5 GPa, and at most 20% by mass of a matrix material, the area density of a monolayer is at least 25 g / m2 and the direction of the fibers in each monolayer is rotated with with respect to the direction of the fibers in an adjacent monolayer.

Description

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DESCRIPTION

Molded article with curved ballistic resistance

The present invention relates to a molded article with curved ballistic resistance comprising at least two sheets with ballistic resistance.

A laminate with ballast resistance comprises a stack of at least 4 monolayers, each monolayer containing unidirectionally oriented reinforcing fibers containing a maximum of 20% by mass of a matrix material, and the direction of the fibers in each monolayer rotated with respect to the direction of the fibers in an adjacent monolayer. A sheet with such a ballistic resistance is very suitable for use in compressed or molded articles with ballistic resistance such as panels and especially curved panels.

A sheet with such a ballistic resistance is known from WO 2005 066401, which constitutes a starting point for independent claim 1, and US 4,623,574. This publication discloses the fabrication of sheets with ballistic resistance by cross-application and stacking of a plurality of monolayers, each with unidirectionally aligned extended chain polyethylene fibers and a matrix material, followed by pressing it into a sheet. Example 1 of this disclosure mentions the production of a monolayer by helically wrapping polyethylene fibers side by side in a drum winder, whereby a Kraton D1107 solution was used to coat the unidirectionally aligned fibers. A plurality of the monolayers thus obtained were stacked, whereby the direction of the fibers in a monolayer is perpendicular to the direction of the fibers in an adjacent monolayer. The obtained stack was placed between parallel plates in an Apollo press and pressed with a pressure of 0.6 MPa at a temperature of 130 ° C for 5 minutes, followed by cooling.

WO 2008/077605 discloses sheets with ballast resistance stacked to form a set and sewn in the corners.

EP1627719A describes materials with ballast resistance produced from a tape, formed in turn by compacted ultrahigh molecular weight polyethylene powder.

There is a continuous motivation towards molded articles with improved ballistic resistance and the present inventors have surprisingly found a laminate with ballistic resistance that allows the manufacture of molded articles with curved ballistic resistance with improved moldability. Improved moldability means that after the molding of an article with curved ballistic resistance, comprising several sheets with ballistic resistance of the invention, a homogeneous product is obtained; This can be determined with the naked eye, for example, by the absence of non-homogeneous coverage of the sheets with ballistic resistance in said article after molding.

According to the present invention, a molded article with improved curved ballistic resistance comprising at least two sheets with ballistic resistance, in which each sheet is provided with ballistic resistance, comprising a stack of at least 4 monolayers, each monolayer containing

Unidirectionally oriented reinforcing fibers with a tensile strength of between 3.5 and 4.5 GPa and at most 20% by mass of a matrix material,

the area density of a monolayer of at least 25 g / m2

and the direction of the fibers in each monolayer being rotated with respect to the direction of the fibers in an adjacent monolayer.

The laminated ballistic resistance used to produce a molded article with curved ballistic resistance according to the invention provides good moldability.

This can be seen after the molding of an article with curved ballistic resistance, which comprises several sheets with stacked ballistic resistance used to produce the molded article with curved ballistic resistance of the invention, obtaining a homogeneous molded article without irregular folding of the sheets with ballistic resistance . An additional advantage is that the ballistic resistance sheet used to produce the molded article with curved ballistic resistance according to the invention shows an additional improved bulletproof performance.

In the present invention, the term "monolayer" refers to a layer of unidirectionally oriented reinforcing fibers and a matrix material that basically holds the fibers together.

A laminate with ballast resistance comprises a stack of at least 4 monolayers, the at least 4 monolayers being preferably linked or joined together. The monolayers are stacked in such a way that the direction of the fibers in each monolayer is rotated with respect to the direction of the fibers in a monolayer

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adjacent. The angle of rotation, which means the smallest angle formed by the fibers of adjacent monolayers, is preferably between 0 ° and 90 °, more preferably between 10 ° and 80 °. Most preferably, the angle is between 45 ° and 90 °.

The fibers in the laminate with baftstica resistance used to produce the molded article with curved baftstica resistance of the invention have a tensile strength of between 3.5 and 4.5 GPa. The fibers preferably have a tensile strength between 3.6 and 4.3 GPa, more preferably between 3.7 and 4.1 GPa or most preferably between 3.75 and 4.0 GPa.

The fibers may be inorganic or organic fibers. Suitable inorganic fibers are, for example, glass fibers, carbon fibers and ceramic fibers.

Suitable organic fibers with such a high tensile strength are, for example, aromatic polyamide fibers (also often referred to as aramid fibers), especially poly (p-phenylene teraphthalamide), liquid crystalline poftimer and ladder type fiber fibers. such as polybenzimidazoles or polybenzoxazoles, especially poly (1,4-phenylene-2,6-benzobisoxazole) (PBO), or poly (2,6-diimidazo [4,5-b-4 ', 5'-e] pyridinylene-1 , 4- (2,5-dihydroxy) phenylene) (PIPD; also called M5) and fibers of, for example, polyolefins, polyvinyl alcohol and polyacrylonitrile which are highly oriented, as obtained, for example, by a gel spinning process. Preferably highly oriented polyolefin, aramid, PBO and PIPD fibers, or a combination of at least two thereof are used.

Even more preferably, high-performance polyethylene fibers or very stretched polyethylene fibers consisting of polyethylene filaments that have been prepared by a gel spinning process are used, as described, for example, in GB 2042414 A oWO 01/73173. The advantage of these fibers is that they have a very high tensile strength combined with a light weight, so that they are in particular very suitable for use in articles with light weight baftstic resistance.

Most preferably, use is made of multifilament yarns of linear polyethylene of ultra high molar mass with an intrinsic viscosity of at least 5 dl / g.

The title of a single filament of these fibers or threads is preferably a maximum of 2 denier, more preferably the title of a single filament of these fibers is a maximum of 1.9 denier. This results in a better moldability of the molded article with curved baftstica resistance comprising the sheet with baftstica resistance. Most preferably, the title of a single filament of these fibers is a maximum of 1.8 denier.

The term matrix material refers to a material that joins or holds the fibers together and can wrap the fibers in whole or in part, so that the structure of the monolayer is preserved during the handling and processing of preformed sheets. The matrix material material may have been applied in various ways and ways; for example as a film between fiber monolayers, as a cross adhesive strip between the unidirectionally aligned fibers or as transverse fibers (transverse with respect to the unidirectional fibers), or by impregnating and / or embedding the fibers with a matrix material.

In a preferred embodiment, the matrix material is a polymeric matrix material, and may be a thermosetting material or a thermoplastic material, or mixtures of the two. The elongation at break of the matrix material is preferably greater than the elongation of the fibers. The matrix material preferably has an elongation of 3 to 500%. In another preferred embodiment, the matrix material is a polymeric matrix material that preferably has an elongation of at least 200%, more preferably from 300 to 1500%, more preferably from 400 to 1200%. From the group of thermosetting materials, preferably vinylic esters, unsaturated polyester, epoxy compounds or phenolic resins are selected as matrix material. From the group of thermoplastic materials, preferably polyurethanes, polyvinyls, polyacrylic compounds, polyolefins or thermoplastic elastomeric block co-polymers such as polyisopropene-polyethylene-butylene-polystyrene or polystyrene-polystyrene-polystyrene block copolymers are preferably selected as matrix material.

More preferably, the matrix material in the article according to the invention has a 100% module of at least 3 MPa. It is understood that this is a secant module measured according to ISO 527 at a 100% strain.

Particularly suitable are those matrix materials that can be applied as dispersion in water. Examples of suitable thermoplastic materials include: acrylates, polyurethanes, modified polyolefins and ethylene vinyl acetate. Preferably, the matrix material contains a polyurethane. More preferably, the polyurethane is a polyetherurethane, which is based on a polyether diol. This provides good performance over a wide range of temperatures. In a special embodiment, the polyurethane or polyetherurethane is based on aliphatic diisocyanates since this further improves the performance of the product, especially its chromatic stability.

Preferably the 100% module is at least 5 MPa. The 100% module is generally less than 500 MPa.

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The amount of matrix material in the monolayer is a maximum of 20% by mass. This results in a good combination of basic performance and moldability. Preferably, the amount of matrix material in the monolayer is at most 18.5% by mass; more preferably at most 17.5% by mass. This results in an even better combination of ballistic performance and moldability. Most preferably, the amount of matrix material in the monolayer is at most 16% by mass. This results in the best combination of ballistic performance and moldability of the molded article with ballistic resistance.

It was found that in order to achieve the required moldability, the weight, or area density, of the monolayer has to be at least 25 g / m2 Preferably, the weight of the monolayer is between 30 and 200 g / m2 More preferably, the weight of the monolayer is between 30 and 180 g / m2. Most preferably, the weight of the monolayer is between 40 and 150 g / m2.

For the manufacture of the laminated ballistic strength used to produce the molded article with curved ballistic resistance according to the invention, the unidirectional reinforcing fibers are impregnated with the matrix material for example by applying one or more plastic films on top, the lower part or on both sides of the plane of the fibers and then passing these, together with the fibers, through heated pressing rollers. Preferably, however, the fibers, after parallel orientation in a plane, are coated with an amount of a liquid substance containing the matrix material. The advantage of this is that a faster and better impregnation of the fibers is achieved. The liquid substance may be, for example, a solution, a dispersion or a melt of the plastic. If a solution or dispersion of the plastic is used in the manufacture of the monolayer, the process also includes evaporating the solvent or dispersant. In this way a monolayer is obtained. Subsequently, at least 4 such monolayers are stacked in such a way that the direction of the fibers in each monolayer is rotated with respect to the direction of the fibers in an adjacent monolayer. Finally, stacked monolayers are treated so that they bind or bond with each other. A suitable treatment may be to press or laminate the stack at a temperature high enough to obtain adhesion. Generally, a higher temperature will provide better adhesion. Adhesion can be further increased by applying some pressure. Adequate pressure and temperature can be found through some routine experiments. In the case of high performance polyethylene fibers, such temperature may not exceed 150 ° C.

The laminate with ballistic resistance can be stacked properly and compressed to form a molded article with curved ballistic resistance. By molded articles with curved ballistic resistance is meant shaped pieces, comprising at least two sheets with ballistic resistance used to produce the molded article with curved ballistic resistance according to the invention, which can be used, for example, as a panel for use in for example a vehicle, especially a curved panel, a hard insert for example for use in protective clothing and bulletproof vests, etc. All these applications offer protection against ballast impacts such as bullets and bullet fragments.

The invention relates to a molded article with curved ballistic resistance comprising at least two sheets with ballistic resistance. In order for the molded article with curved ballistic resistance to have a good ballistic resistance, the number of sheets with ballistic resistance in the article is at least 10, more preferably at least 15 and most preferably at least 20.

Generally the molded article with curved ballistic resistance of the invention will not have a thickness greater than 125 mm; preferably it will not have a thickness greater than 100 mm and more preferably it will not have a thickness greater than 80 mm.

The molded article with curved ballistic resistance according to the invention can be suitably combined with a ceramic layer and / or a metal layer. Said metal and / or ceramic layer is then placed on the side of the molded article with ballistic resistance directed towards the ballistic impact, that is to say as an impact face.

In the event that the molded article with curved ballistic resistance according to the invention is used in ballistic applications where a threat of armor piercing bullets can be found, the impact face is preferably a ceramic layer. In this way, an article with a layered structure is obtained as follows: ceramic layer / sheets with compressed stacked ballistic resistance. Optionally, a metal layer may be present as an additional layer between the ceramic layer and the compressed stacked compressed ballast sheets.

Suitable ceramic materials include, for example, alumina oxide, titanium oxide, silicon oxide, silicon carbide, silicon nitride and boron carbide. The thickness of the ceramic layer depends on the level of ballistic threat, but is generally between 2 mm and 30 mm. This composite article will preferably be positioned so that the ceramic layer is directed towards the ballistic threat.

Suitable metals include aluminum, magnesium, titanium, copper, nickel, chromium, beryllium, iron including its alloys, such as for example steel and stainless steel, and aluminum alloys with magnesium (the so-called

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5000 series aluminum) and aluminum alloys with zinc and magnesium or with zinc, magnesium and copper (the so-called 7000 series aluminum).

During the process to produce a molded article with curved baftstica resistance, the stacked baftstica resistance sheets used to produce the molded article with curved baftstica resistance according to the invention can be suitably compressed at a pressure of more than 16.5 MPa, in a Press or compression molding machine. Preferably, the pressure is at least 20, or at least 25 MPa, since this additionally enhances the plastic strength of the molded article. The temperature during compression is preferably between 125 and 150 ° C. A higher temperature has the advantage that the compression time can be further reduced, but such a higher temperature must remain at least 10 ° C below the temperature at which the mechanical properties of the fiber begin to deteriorate. In the case of high-performance polyethylene fibers, the temperature should not exceed 150 ° C, that is, remain below the melting range of the fibers. In a preferred embodiment, the stack preferably comprising a polyurethane matrix material is compressed for at least 60 minutes at a temperature between 125 and 135 ° C. After pressing at an elevated temperature, before removing it from the press, the battery is cooled to a temperature below 100 ° C, preferably below 80 ° C. In a preferred embodiment, the stack is cooled while still under pressure, preferably at least 5 MPa, more preferably under the same as in the previous pressing step.

Finally, the invention relates to a protective garment, such as a bulletproof vest, which comprises the molded article with curved baffletic resistance of the invention in the form of a hard panel.

The test methods referred to in this application are as follows:

• VI: the internal viscosity is determined according to the method PTC-179 (Hercules nc. Rev. April 29, 1982) at 135 ° C in decalin, the dissolution time being 16 hours, with DBPC as antioxidant in an amount of 2 g / l of solution, extrapolating the viscosity as measured at different concentrations at zero concentration;

• Tensile properties (measured at 25 ° C): the tensile strength (or resistance), the tensile modulus (or modulus) and the elongation at break are defined and determined in multifilament threads as specified in the ASTM D885M standard, using a nominal fiber gauge length of 500 mm, a feed rate of 50% / min. Based on the measured stress-strain curve, the module is determined as the gradient between 0.3 and 1% strain. For the calculation of the module and the resistance, the measured tensile forces are divided between the title, as determined by weighing 10 meters of fiber; GPa values are calculated assuming a density of 0.97 g / cm3. The tensile properties of thin films are measured according to ISO 1184 (H).

• The matrix material module was determined according to ISO 527. The 100% module was determined in strips of film with a length of 100 mm (free length between the fasteners) and a width of 24 mm. The 100% module is the secant module measured between 0% and 100% deformations.

The invention will now be explained further with the following example and comparative experiment, without being limited thereto.

Example 1

First, a unidirectional monolayer was developed in a drum winder. For this, a siliconized paper was attached to the drum of the drum winder. The drum had a circumference and a width that were both 160 cm. A polyethylene thread with a toughness of 3.6 GPa and a 1.92 denier per filament title around the drum winder with a separation of 3.08 mm was wound. Before winding around the drum, the thread was moistened with a dispersion of styrene-isoprene-styrene block copolymer in water. By diluting the dispersion, the amount of solids absorbed by the yarn was adjusted to 18% by weight with respect to the amount of yarn.

All the water was evaporated by heating the drum to ~ 65 ° C. In doing so, a monolayer with a thread area density of 48.6 g / m2 and a matrix area density of 10.7 g / m2 was developed.

Before adding the second monolayer, the first monolayer was removed from the drum, turned 90 ° and attached to the drum again. Using the same procedure, a second monolayer adhered to the first monolayer winding thread around the drum. The threads of the second layer are oriented essentially perpendicular to the threads in the first monolayer. This procedure was repeated to add a third and fourth monolayer.

The final sheet, that is the bulletproof sheet used to produce a molded sturdy molded article according to the invention, consisted of 4 monolayers oriented in a direction of 0 ° / 90 ° / 0 ° / 90 °. Subject an area density (DA) of 237.4 g / m2.

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In total 67 such final sheets of 40x40 cm were stacked together and pressed to give a bulletproof panel.

The pressing conditions to obtain the bulletproof panel were the following:

The stack with the final 67 sheets was placed between two plates of a standard press. The temperature of the dishes was between 125-130 ° C. The package was retained in the press until the temperature in the center of the package was between 115-125 ° C. Subsequently, the pressure was increased to a compression pressure of 30 MPa and the package was kept under this pressure for 65 min. Subsequently, the package was cooled to a temperature of 60 ° C at the same compression pressure.

The area density of the pressed panel was 15.9 kg / m2 The area density of thread in the panel was 13 kg / m2

The panels obtained were subjected to a firing test according to the procedure set forth in STANAG 2920. A 7.62 x 39 mm soft steel core bullet, often also referred to as "AK47 MSC bullet", was used. The bullet was obtained from Messrs Sellier & Belliot, Czech Republic. These tests were performed with the purpose of determining a V50 and / or the absorbed energy. V50 is the speed at which 50% of the projectiles will penetrate the armor plate. The test procedure was as follows. The first projectile was fired at the anticipated V50 speed. Actual speed was measured shortly before impact. If the projectile is detected, a next projectile is fired at an expected speed of approximately 10% more. If drilling, the next projectile was fired at an expected speed of approximately 10% less. The actual impact speed was always measured. V50 was the average of the two highest stops and the two lowest penetrations. The shielding performance was also determined by calculating the kinetic energy of the projectile at V50 and dividing this by the DA of the plate, the so-called “Eabs”.

The panel V50 was found to be 782 m / s, and the Eabs was 186 J m2 / kg.

Comparative Experiment A

The same procedure as described in Example 1 was used to make a laminate, except that the tenacity of the thread was 3.3 GPa and a title of 3.3 denier per filament, the matrix content was 22% and the spacing between threads was 6.08 mm. This resulted in a sheet comprising 4 monolayers, each monolayer having a thread area density of 24.3 g / m2 and a matrix area density of 6.9 g / m2.

Pressing 134 sheets obtained a panel with an area density of 16.7 kg / m2 and a wire DA of 13.0 kg / m2. The DA of yarn was equal to the DA of yarn in example 1.

The panel V50 was found to be 666 m / s, the Eabs was 142 J m2 / kg.

These results show that despite the same amount of polyethylene fiber in the panel, namely 13 kg / m2, the panel according to the invention in example 1 showed a significant higher Eabs.

 Table 1

 Example 1 Comp. TO

 Tensile strength

 [GPa] 3.6 3.3

 No. of monolayers per sheet

 [-] 4 4

 Matrix mass%

   18 22

 DA of thread per monolayer

 [g / m2] 48.6 24.3

 Matrix DA by

 [g / m2] 10.7 6.9

 monolayer

 Monolayer DA

 [g / m2] 59.4 31.2

 DA per sheet

 [g / m2] 237.4 124.9

 N ^ of sheets per package

   67 134

 Package DA

 [kg / m2] 15.9 16.7

 DA of thread in the package

 [kg / m2] 13.0 13.0

 V50

 [m / s] 782 683

 Thread eabs

   188 143

Claims (10)

5 10 fifteen twenty 25 30 35 40 1. - A molded article with curved baKstica resistance comprising at least two sheets with baustic resistance, in which each lamina with ballast resistance comprises a stack of at least 4 monolayers, each monolayer containing Unidirectionally oriented reinforcing fibers with a tensile strength of between 3.5 and 4.5 GPa, and at most 20% by mass of a matrix material, the area density of a monolayer is at least 25 g / m2 and the direction of the fibers in each monolayer being rotated with respect to the direction of the fibers in an adjacent monolayer. 2. - The molded article with curved ballistic resistance according to claim 1, wherein the area density of a monolayer is at least 40 g / m2. 3. - The molded article with curved ballistic resistance according to claim 1 or 2, wherein the monolayer comprises a maximum of 18.5% by mass of the matrix material. 4. - The molded article with curved ballistic resistance according to any one of claims 1-3, wherein the unidirectionally oriented reinforcing fibers have a tensile strength between 3.6 and 4.3 GPa. 5. - The molded article with curved ballistic resistance according to any one of claims 1-4, wherein the unidirectionally oriented reinforcing fibers are very stretched polyethylene fibers. 6. - The molded article with curved ballistic resistance according to any one of claims 1-5, wherein the matrix material has a 100% module of at least 3 MPa. 7. - The molded article with curved ballistic resistance according to any one of claims 1-6, wherein the title of a single filament of the fibers is a maximum of 2 denier. 8. - The molded article with curved ballistic resistance according to any one of claims 1-6, comprising at least 10 of the sheets with ballistic resistance. 9. - The molded article with curved ballistic resistance according to claim 8, further comprising an impact face made of ceramic or metal. 10. - Protective garment, such as a bulletproof vest, comprising the molded article with curved ballistic resistance according to claim 8 or 9.