IMPROVED BALLISTIC RESISTANT COMPOSITE ARTICLES WITH

POLYDICYCLOPENTADIENE (PDCPD)

FIELD OF THE INVENTION

[001] The present invention relates to ballistic-resistant articles. More specifically, the present invention relates to improved ballistic-resistant composite articles made of polydicyclopentadiene (PDCPD).

BACKGROUND OF THE INVENTION

[002] Composite materials are widely used for ballistic-resistant articles such as bulletproof vests, helmets, armor plate, structural parts of aircrafts, ships, helicopters, and other military components.

Most composite materials that are used for the production of ballistic-resistant articles have relatively high strength and stiffness. These materials are typically made of a reinforcing phase, i.e., fiber such as glass, carbon, aramid and more, and a matrix made of, for instance, phenol, epoxy, or polyester which unites the fibers into a one-piece work and improves the resistance of the fibers against ballistic hits.

SUMMARY OF THE INVENTION

[003] There is thus provided, according to embodiments of the present invention a method for the preparation of a composite article. The method includes placing a plurality of dicyclopentadiene (DCPD) monomers and a ruthenium,[l,3-bis-(2,4,6-trimethylphenyl)- imidazolidinylidene]dichloro(phenylmethylene) (tricyclohexylphosphine) catalyst in a vessel. The method further includes mixing the solution. Then, immersing a fabric in the solution and placing the solution with the fabric in a press for a predefined period of time to produce a composite article of a polydicyclopentadiene (PDCPD) polymer and fibers. If cooling the composite article is necessary, it may optionally be placed in a cooling bath.

[004] Furthermore, according to embodiments of the present invention, the method may further include treating a fabric with vinylsilane prior to immersing it in the above mentioned DCPD monomer solution. The method may include creating a 1% isopropyl alcohol (IP A) in water solution and mixing it via a mechanical mixer for about an hour. A 1% silane in water solution may be added and the mixture may be further mixed for about an hour via a mechanical mixer. Then, a fabric is to be immersed in the solution and to be kept it in the solution for at least several minutes and up to several hours. Then, in order to dry the fabric, it may be kept in an oven for about an hour at a temperature of 120°C.

[005] Furthermore, according to embodiments of the present invention, the method may further include treating the fabric with an acidic solution prior to immersing it in the DCPD monomer solution. The method may include creating an acid with concentration in the range of 0.1% - 10%, preferably in the range of 1% - 6% and most preferably in the range of 4.8% - 5.2%, such as, for instance, acetic acid, in water solution and mixing it via a mechanical mixer for about an hour. Placing a fabric in a vessel, pouring the solution into the vessel and immersing the fabric completely in the solution. The fabric may be kept in the solution for at least a few minutes and up to several hours. Then, to dry the fabric, it may be kept in an oven for about an hour at a temperature of 120°C.

BRIEF DESCRIPTION OF THE DRAWINGS

[006] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[007] Fig. 1 is a flow diagram illustrating a method for producing samples to be tested according to embodiments of the invention;

[008] Figs. 2A-2C present a flow diagram illustrating the method of Fig. 1 with greater details according to embodiments of the invention;

[009] Fig. 3 is a flow diagram illustrating a surface treatment method with a silane-based solution according to embodiments of the invention;

[0010] Fig. 4 is a flow diagram illustrating a surface treatment method with an acid- based solution according to embodiments of the invention;

[0011] Fig. 5 is a bar graph illustration of the results of tensile test No. 1 according to embodiments of the invention;

[0012] Fig. 6 is a bar graph illustration of the results of tensile test No. 2 according to embodiments of the invention; [0013] Fig. 7 is a bar graph illustration of the results of tensile test No. 3 according to embodiments of the invention;

[0014] Fig. 8 is a bar graph illustration of the results of tensile test No. 4 according to embodiments of the invention;

[0015] Fig. 9 is a bar graph illustration of the results of tensile test No. 5 according to embodiments of the invention;

[0016] Fig. 10 is a bar graph illustration of the results of tensile tests No. 5 and 6 according to embodiments of the invention;

[0017] Fig. 11 is a bar graph illustration of the results of tensile test No. 6 according to embodiments of the invention;

[0018] Fig. 12 is an illustration of a curve of breaking energy versus percent concentration of a catalyst and a curve of Young's modulus versus percent concentration of a catalyst according to embodiments of the invention;

[0019] Fig. 13 is a bar graph illustration of the results of tensile test No. 7 according to embodiments of the invention;

[0020] Fig. 14 is an illustration of curves of mechanical properties of samples kept under tensile stress versus percent concentration of a catalyst according to embodiments of the invention;

[0021] Fig. 15 is a bar graph illustration of mechanical properties of samples made of various types of fabrics kept under tensile stress according to embodiments of the invention;

[0022] Fig. 16 is a bar graph illustration of the results of flexural test No. 1 according to embodiments of the invention;

[0023] Fig. 17 is a bar graph illustration of the results of flexural test No. 2 according to embodiments of the invention;

[0024] Fig. 18 is a bar graph illustration of the results of flexural test No. 4 according to embodiments of the invention;

[0025] Fig. 19 is a bar graph illustration of the results of DSC test No. 1 according to embodiments of the invention;

[0026] Fig. 20 is a bar graph illustration of the results of DSC test No. 2 according to embodiments of the invention;

[0027] Fig. 21 is an optical image illustrating surface morphology of a sample treated with a "new" catalyst according to embodiments of the invention; [0028] Fig. 22 is a bar graph illustration of the results of DSC test No. 3 according to embodiments of the invention;

[0029] Fig. 23 is a bar graph illustration of the results of DSC test No. 4 according to embodiments of the invention;

[0030] Fig. 24 is a bar graph illustration of the results of DMA test No. 1 according to embodiments of the invention;

[0031] Fig. 25 is an illustration of a curve of (T _g ) versus percent concentration of the catalyst according to embodiments of the invention;

[0032] Fig. 26 is an illustration of curves of storage modulus versus percent concentration of the catalyst according to embodiments of the invention;

[0033] Fig. 27 is an optical image illustrating a surface of a sample through which a projectile has passed in ballistic test No. 1 according to embodiments of the invention;

[0034] Fig. 28 is a bar graph illustration of the results of ballistic test No. 2 according to embodiments of the invention;

[0035] Fig. 29 is an optical image illustrating a surface of a sample which was hit by a projectile;

[0036] Fig. 30 is an optical image illustrating various color shaded-surface through which a projectile has left a sample;

[0037] Fig. 31 is a bar graph illustration of the results of ballistic test No. 3 according to embodiments of the invention;

[0038] Fig. 32 is an optical image illustrating multiple blown up regions of a surface from which projectiles have ejected according to embodiments of the invention;

[0039] Fig. 33 is an optical image illustrating various color shaded-surface from which projectiles have ejected according to embodiments of the invention;

[0040] Fig. 34 is a bar graph illustration of the results of ballistic test No. 4 according to embodiments of the invention; and

[0041] Figs. 35A-35C are optical microscopy images, each illustrating a surface profile of a surface from which a projectile has ejected according to embodiments of the invention. DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0042] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0043] When a ballistic-resistant article is hit with a ballistic body, tension and/or shear forces may induce breakage of the article. More specifically, when a projectile hits an article and tries to pass through it, either tensile and/or shear modes may get activated. However, since in general tensile-induced breakage may absorb a greater amount of energy, it is tension that may most likely govern the breakage mechanism.

[0044] When an article is made of a rigid material, its resistance to distorting means may be relatively high. Therefore, a projectile hitting an article made of a rigid material, may not distort the article but may break it via shear forces. Accordingly, in accordance with embodiments of the present invention, a ballistic resistant article is to be made of a relatively soft and flexible composite material in order to avoid or minimize the effect of the shear forces.

[0045] Most of today's matrices which are used for ballistic resistant articles are made of thermoset materials. Such materials are advantageous for providing relatively high degree of wetting when in contact with a reinforcing phase and for creating physical bonds with the reinforcing phase, for instance, with aramid fibers. Such physical bonds are being induced via polar segments of the matrix's molecules. These segments are also responsible for inducing cross-linking reactions which take place along the manufacture process of composite materials.

[0046] Thermoset materials currently used for forming ballistic resistant articles are liquids of low viscosity which may be easily absorbed within a reinforcing phase. However, the viscosity of such materials is still relatively high to make wetting of the reinforcing phase to the matrix material a rather difficult task.

[0047] It should be understood that in order to maximize the amount of energy absorbed by a ballistic resistant article upon breakage, a ballistic resistant article should be made of a relatively flexible material (e.g., a composite material). In accordance with embodiments of the present invention, flexibility may be achieved as follow:

1. The components of a composite material should have "good" adhesion to one another so that the product may absorb relatively high amount of energy while its fibers are being extracted as a result of a ballistic hit. However, the adhesion should not be too high so that post a ballistic hit, the distortion mode may be enabled.

2. The matrix should be relatively flexible so that upon a ballistic hit, the involved breakage should be governed by distortion and not via shear.

3. Although the reinforcing phase (fibers) may contribute to the toughness and strength of the final product, the fibers should be left somewhat flexible to avoid breaking upon a ballistic hit.

[0048] Polydicyclopentadiene (PDCPD) polymer is a thermoset material which may be advantageous over materials currently used for making matrices for ballistic- resistant articles for the following reasons:

1. Most thermoset materials may contain polar segments which may improve the adhesion between such materials and aramid fibers. In addition, some of these materials may contain rigid segments such as benzene rings which undesirably harden the final product. In contrast, a PDCPD polymer is a thermoset material which does not contain polar segments. Instead, it contains monomers that form a liquid of relatively low viscosity compared to most other thermoset materials. A relatively low liquid viscosity may improve the wetting capabilities, thus, the adhesion of the PDCPD polymer to various fibers.

2. The PDCPD polymer is made of only Carbon and Hydrogen atoms. The molecular weight of Carbon and Hydrogen atoms is relatively low compared to the molecular weight of Nitrogen and Oxygen atoms which are the building blocks of most thermoset materials available nowadays. Therefore, the PDCPD polymer has a relatively low weight and a relatively low density of approximately 1.03gr/cm ³ which is lower than the density of most other thermoset materials. It should be noted that epoxy and phenol, for instance, are characterized with a density that is higher by approximately 45% than the density of the PDCPD polymer.

3. The manufacturing process of a PDCPD matrix may include heating the DCPD monomers for decreasing the time prior to which the reaction is initiated and thus for decreasing the total manufacture time. This way, the DCPD monomers may solidify within several minutes unlike some of the available matrices nowadays which require a total manufacture time as long as about 24 hours.

[0049] In accordance with embodiments of the present invention, to better understand the characteristics of the PDCPD matrix and the reciprocation between the matrix and the fibers, various analyses such as for instance mechanical and thermal analyses were carried out prior to testing the ballistic resistance of samples containing a PDCPD matrix.

[0050] Mechanical tests may be important for determining the strength of a material, its stiffness and its ability to absorb energy. However, it should be understood that mechanical tests do not reveal the characteristics of the material and the way it may function while in a ballistic test or while under ballistic conditions. The velocity at which a tensile test is carried out, for instance, is lower than the velocity of a ballistic body. However, relating the mechanical test results to ballistic test results may lead to a reduced number of ballistic tests as well as to a decrease in the time required for preparing samples to be used in ballistic tests.

[0051] TENSILE TESTS - in accordance with embodiments of the present invention, tensile tests were carried out with a device named "Inston 4481" made by Inston High Wycombe, England, at a tensile velocity of lmm/min by the ASTM D-638 standard. In addition, the Inston 4481 has been used for testing composite materials having a matrix made of PDCPD Kevlar49 with a tensile velocity of 2mm/min.

[0052] FLEXURAL TEST - in accordance with embodiments of the present invention, fiexural tests were carried out with the same device used for performing tensile tests, i.e., Inston4481. The testing velocity was 2mm/min and the samples used were of the following dimensions: 15cm in length, 12.5 mm in width and 3-4 mm in thickness.

[0053] THERMAL ANALYSIS TESTS - in accordance with embodiments of the present invention, thermal analysis tests which involved heating a sample and measuring its mechanical properties and/or its enthalpy were carried out in order to estimate the degree of polymerization (i.e., the degree of cross-linking) of the DCPD monomer. A crosslinked PDCPD polymer was obtained by metathesis polymerization of the DCPD monomer which comprised a ring-opening and an exchange of alkylene fragments across a double bond of the DCPD monomer.

[0054] DIFFERENTIAL SCANNING CALORIMETRY (DSC) TEST - in accordance with embodiments of the present invention, DSC tests were performed with a device named TA Q200 made by TA Instruments, New Castle, Delaware, USA. Samples which were previously undergoing mechanical tests such as a tensile test were weighed and heated to various temperatures above the glass transition temperature (T _g ) of the PDCPD at a heating rate of 20°C/min. It should be noted that in some cases, the test was carried out in two heating cycles, i.e., after the first heating cycle, the sample was cooled to 25°C and then was reheated to a desired temperature at the same heating rate.

[0055] DIFFERENTIAL MECHANICAL ANALYSIS (DMA) TEST - in accordance with embodiments of the present invention, Perker Elmer DMA e7-type device, made by PerkinElmer Life and Analytical Sciences, Waltham, Massachusetts, USA, was used for carrying DMA tests. These tests were carried out on PDCPD (without fibers) which were dynamically flexural while being heated at a heating rate of 20°C/min with a frequency of lHz.

[0056] BALISTIC TESTS - In accordance with embodiments of the present invention, ballistic tests of the American V50-type tests by the Military standard 662 -F were performed. Ballistic tests were performed on samples which have previously undergoing at least one of the above mentioned tests.

Ballistic tests, in accordance with embodiments of the present invention, were carried out in order to compare the PDCPD matrix to the epoxy matrix which is widely used for ballistic resistance articles. For this reason, the inventors aimed at: (a) using similar manufacturing processes for making PDCPD matrices and epoxy matrices, (b) preparing samples with same number of fabric layers, and (c) preparing samples with similar fiber concentration and similar fiber weight per unit area. In these tests a projectile made of a rigid metal having a weight of about 1.1 gr and a truncated head was fired towards a target sample. The flight velocity of the projectile was determined via laser detection.

[0057] MICROSCOPY TESTS - in accordance with embodiments of the present invention, samples have been sawn at regions adjacent to cuts created by projectiles. This was done in order to enable visualizing the cut and getting an understanding of the mechanism employed while the projectile hit and penetrated through the composite material.

[0058] FTIR TESTS - in accordance with embodiments of the present invention, FTIR tests were carried out for diagnosing differences in molecular segments within the samples. Such diagnoses may increase the degree of understanding of the reaction, the possible disturbing means to the reaction, and some structural variations of the fibers that may cause the formation of various products.

Referring to Fig. 1 which is a flow diagram illustrating a method for producing samples to be tested according to embodiments of the invention. The method may comprise placing a plurality of dicyclopentadiene (DCPD) monomers in a vessel (block 102), adding a δ mthenium,[l,3-bis-(2,4,6-trime ^

(tricyclohexylphosphine) catalyst to the vessel (block 104), placing the solution of the monomer and the catalyst in a press (block 106), immersing a fabric in the solution (block 108), placing the fabric while in the solution in a press to produce a composite article of a polydicyclopentadiene (PDCPD) polymer and fibers (block 110), and placing a composite article in a cooling bath (block 1 12).

[0059] Referring to Figs. 2A-2C which present a flow diagram illustrating the method of Fig. 1 with greater details according to embodiments of the invention. The method may comprise placing a plurality of DCPD monomers in a vessel (202), adding a catalyst named ruthenium,[l,3-bis-(2,4,6-trimethylphenyl)-imidazolidinylide ne]dichloro

(phenylmethylene)(tricyclohexylphosphine) to the vessel (block 204), mixing the solution manually for about 30 seconds (block 206). Charging the solution into a mold such as, for example, an Aluminum mold or to a similar forming container in which the DCPD polymerizes and covering it with a cover such as, for instance, an Aluminum cover (block 208), placing the mold in a press which is to be operated under increased pressure and temperature conditions (block 210). When the final product is to contain an aramid fabric, charging DCPD solution into a mold (block 212), immersing an aramid fabric in the DCPD monomer solution (block 214), saturating the aramid fabric with the DCPD monomer solution (block 216), pouring some more DCPD monomer solution on top of the aramid fabric (block 217) repeating step 217 till the aramid fabric is saturated with the DCPD monomer solution (block 218). Covering the mold with a cover (block 220), placing the mold inside a press which is to be operated under increased temperature and pressure conditions (block 222), after a defined period of time which is required for inducing cross- linking of the DCPD monomers, removing the mold from the press and placing it into a cooling bath (block 224). Fiber concentration in a sample (i.e., in a composite article) may be obtained by cutting the edges of the sample in order to avoid regions of varying fiber concentration (block 226), weighing the sample and measuring its length and width dimensions (block 228), sawing the sample into pieces such as, for instance, rectangular shaped pieces (block 230).

In case of PDCPD samples without fibers, a milling machine is to be used for shaping the pieces into a desired shape such as for instance a shape of a paddle (block 232), in case of a sample made of a composite material (i.e., PDCPD and fibers), using a milling machine for eliminating defects which may be created during the sawing process (block 234).

[0060] The inventors used commercially available products such as Prometa 2100 (hereinafter referred to as "an old catalyst") and Prometa 2500 (hereinafter referred to as "a new catalyst") manufactured by Materia Inc, San Gabriel Blvd Pasadena, USA.

[0061] Each of these products contained the following catalyst: ruthenium, [l ,3-bis-(2,4,6- trimethylphenyl) imidazolidinylidene] dichloro (phenyl methylene) (tricyclohexylphosphine). However, it should be noted that other commercially available products containing a ruthenium, [l,3-bis-(2,4,6-trimethylphenyl) imidazolidinylidene] dichloro (phenylmethylene) (tricyclohexyl phosphine) may also be used.

[0062] It should be noted that the ruthenium, [l,3-bis-(2,4,6-trimethylphenyl) imidazolidinylidene] dichloro (phenylmethylene) (tricyclohexylphosphine) catalyst is advantageous for barely getting oxidized while in contact with Oxygen and thus does not limit a working environment to an Oxygen-free environment.

[0063] It should also be noted that some samples were made of fabrics which were undergoing surface treatment.

[0064] Referring now to Fig. 3 which is a flow diagram illustrating a method used for surface treating samples with a silane-based solution according to embodiments of the present invention. More specifically, Fig. 3 illustrates a flow diagram of a method used for saturating a fabric with a compound of silane such as for instance vinylsilane according to embodiments of the present invention. The method may comprise: creating a 1% isopropyl alcohol (IP A) in water solution and mixing it via a mechanical mixer for about an hour (block 302). Then, a 1% silane in water solution may be added and the mixture may be further mixed for about an hour via a mechanical mixer (block 304). Immersing a fabric in the solution and keeping it in the solution for at least several minutes and up to several hours (block 306). Then, in order to diy the fabric, it may be kept in an oven for about an hour at a temperature of 120°C (block 308).

[0065] Referring now to Fig. 4 which is a flow diagram illustrating a method used for surface treating samples with an acidic solution according to embodiments of the present invention. The method may comprise: creating a 5% acid in water solution and mixing it via a mechanical mixer for about an hour (block 402). Placing a fabric in a vessel, pouring the solution into the vessel and immersing the fabric completely in the solution (block 404). The fabric may be kept in the solution for at least a few minutes and up to several hours (block 406). Then, to dry the fabric, it may be kept in an oven for about an hour at a temperature of 120°C (block 408).

[0066] It should be noted that in case of samples made of Epoxy/Kevlar49, the used vessel has to be made of a material having a relatively low surface energy such as, for instance, Polytetrafluoroethylene (PTFE) in order to avoid the sample from sticking to the vessel. In addition, thin layer(s) of silicon may be created at the surface of the vessel to further eliminate possible sticking of the sample to the vessel. TEST RESULTS:

[0067] VISUAL TESTS:

1. A sample made of PDCPD/Kevlar49 seemed to be more flexible than a PDCPD sample without fibers.

2. Varying the processing pressure may not vary the flexibility of a sample.

3. A two-stage process, in accordance to embodiments of the present invention, where in the first stage every fabric layer was immersed in a DCPD monomer solution and was undergoing cross-linldng, and in the second stage all fabric layers were immersed in a DCPD monomer solution and were concurrently undergoing cross-linldng. A two-stage process as such may increase the degree of cross-linldng in a sample, thus, may produce a sample with a greater Young's modulus value.

4. The final product may improve if a two-stage process were to take place. In the first stage, a fabric was to be saturated with a catalyst solution (10% catalyst in acetone solution), dried and saturated with a DCPD solution. In the second stage, the DCPD monomer was to undergo cross-linldng.

5. Treating the fabric with an acidic solution and drying it prior to immersing it into a DCPD solution may significantly improve physical properties such as tensile stress, flexural stress, Young's modulus as well as thermal properties such as Tg values (increased Tg value) of the final product.

6. Keeping the catalyst in a cool place prior to using it may improve the results compared to if the catalyst was kept at room temperature prior to being used. It should be noted that a catalyst that was kept at room temperature and was cooled prior to being used, did not improve the results.

TENSILE TESTS:

[0068] The catalyst "poisoning" phenomenon which was observed in previous visual tests made the inventors to modify the production process. To avoid "poisoning" of the catalyst, the inventors tried treating the aramid fibers with vinylsilane for forming a vinylsilane layer(s) on the top surface of the aramid fibers. Such vinylsilane layer(s) may bond with the DCPD monomer and may act as "buffer" layer(s) between the aramid fibers and the DCPD monomers. Bonding between the vinylsilane molecule and the DCPD monomer was induced basically by opening a double bond of the vinylsilane and by opening a double bond of the DCPD monomer.

The inventor also tried treating the samples with an acidic solution such as, for instance, an acetic acid solution in order to avoid "poisoning" of the catalyst.

In addition, the inventors have tried using octyltrimethyloxysilane in order to improve the adhesion of the DCPD monomers to aramid fibers, i.e., by creating physical bondings between the DCPD monomers and the aliphatic parts of the silane. Treating the aramid fibers with octyltrimethyloxysilane included immersing the fibers in an octyltrimethyloxysilane solution and than drying them.

TENSILE TEST No. 1

[0069] Table 1 provides a brief description of manufacturing process conditions used for preparing PDCPD and PDCPD/Kevlar49 samples to be used in tensile test No. 1

Table 1 : manufacturing process conditions used for preparing PDCPD and PDCPD/Kevlar49 samples for tensile test No. 1.

3. 2% non-fresh catalyst

4. Curing temperature of 120°C for 60 minutes for inducing

cross-linking

3 1. 2 % catalyst

2. Curing temperature of 120°C for 60 minutes for inducing

cross-linking

4 1. Immersing fabric in 5% acetic acid and drying

2. 2 % catalyst

3. Curing temperature of 120°C for 60 minutes for inducing

cross-linking

5 1. Immersing fabric in DCPD & 2 % catalyst) and diying

2. 2 % catalyst

3. Curing temperature of 120°C for 60 minutes for inducing

cross- linking

6 1. Immersing in fresh catalystand drying

2. 2 % catalyst

3. Curing temperature of 120°C for 60 minutes for

inducing cross-linking

Reference is now made to Fig. 5 which is a bar graph illustration of the results of tensile test No. 1 according to embodiments of the invention.

Based on the results, the inventors concluded:

1. The catalyst should be kept in a cool place.

2. A two-stage treatment, i.e., a first stage during which cross-linking is induced in each one of the fabric layers separately followed by a second stage during which cross- linking is induced concurrently in all fabric layers, may improve the properties of the composite material.

3. Immersing the fabric in a 5% acetic acid solution may be advantageous over a 1% acetic acid solution. 4. Previous work has shown better toughness values but lower values of energy of absorption at break. Based on that, the inventors assumed that the catalyst had to be replaced. TENSILE TEST No. 2

[0070] PDCPD samples without fibers were prepared with various catalyst concentrations. These samples were tested in order to determine the effect of the catalyst concentration on the mechanical properties of the samples. In addition, PDCPD/Kevlar49 samples were also tested in order to determine the parameter(s)/experimental condition(s) which may improve their mechanical properties .

Table 2 provides a brief description of manufacturing process conditions used for the preparation of samples used in testile test No. 2.

Table 2: manufacturing process conditions used for preparing samples for testile test No. 2.

and drying

2. Cooled monomer - good wetting. 2% Catalyst

3. 8 fabric layers

4. Curing temperature of 120°C for 60 minutes for

inducing cross-linking

18 1. Immersing fabric in a 5% acetic acid and drying

2. 8 fabric layers

3. 2% Catalyst

4. Curing temperature of 200°C for 60 minutes

for inducing cross-linking

Reference is now made to Fig. 6 which is a bar graph illustration of the results of tensile test No. 2 according to embodiments of the invention.

Based on the results, the inventors concluded:

1. A higher concentration of the catalyst may improve the tensile test results.

2. Tensile test results obtained with PDCPD (without fibers) samples which were produced with a 2% catalyst solution may be better than tensile test results provided by the catalyst manufacturer, i.e., Materia Inc., but may not be as good as tensile test results obtained in previous work.

3. Based on the above, the inventors concluded that the catalyst has aged.

4. Tensile test results obtained with samples 16 and 18 were much better than the results obtained with sample 1.

5. Tensile test results obtained with sample 18 were significantly lower than the results obtained with samples 16 and 17 but higher than results obtained with previous samples. In addition, as seen in the figure, the energy absorbed by sample 18 was relatively lower than the energy absorbed by other samples. This may be due to a high processing temperature which may have degraded the material.

TENSILE TEST No. 3 [0071] It was found in previous flexural and tensile tests that cut profiles in samples with relatively high Young's modulus turned to be different than cut profiles of samples with lower Young's modulus. In order to describe the essence of the difference in the cut profile, it should be noted that the degree of waviness (created by the fibers) at the surface was lower in samples having a relatively high Young's modulus. It was also found that the magnitude of the "waves" was greater in the direction of the warp fibers.

Based on the above, the inventors prepared samples in which the wrap fibers were parallel to the longitudinal direction of the sample.

Table 3 provides a brief description of manufacturing process conditions used for the preparation of samples to be used in tensile test No. 3.

Table 3^ manufacturing process conditions used for preparing the samples for tensile test No.

2. The sample is processed in such a way that the weft fibers

are parallel to the longitudinal direction of the sample

Reference is now made to Fig. 7 which is a bar graph illustration of the results of tensile test

No. 3 according to embodiments of the invention.

Based on the results, the inventors concluded that the direction of the fabric during processing strongly affected the tensile test results which were improved by more than 300%.

[0072] In order to prevent the direction of the fabric from influencing test results, the inventors placed the fabric in such a way that in one test the weft fibers were parallel to the longitudinal direction of the sample and in another test the fabric was rotated so that the wrap fibers were parallel to the longitudinal direction of the sample.

Table 4 provides a brief description of manufacturing process conditions used for the preparation of samples to be used in tensile test No. 4.

Table 4: manufacturing process conditions used for preparing the samples for tensile test No. 4.

6. Curing temperature of 120°C for 60 minutes for

inducing cross-linking

7. Processing the material in a press that is operated at

high temperature and pressure

8. Weft fibers are parallel to the longitudinal direction

of the sample.

Previous work 1. 2% catalyst

2. Curing temperature of 120°C for 60

minutes for inducing cross-linking

Reference is now made to Fig. 8 which is a bar graph illustration of the results of tensile test No. 4 according to embodiments of the invention.

Based on the results, the inventors concluded that:

1. Sample 31 was approximately twice as much tougher than a sample which was produced in a previous set of work and had all of its weft fibers parallel to its longitudinal direction.

2. Octyltrimethoxysilane seemed to increase the material's toughness. TENSILE TEST No. 5

[0073] Tensile test No. 5 was intended for investigating the impact of a "post curing" treatment as well as the effect of octyltrimethoxysilane on the mechanical properties of the samples.

Table 5 provides a brief description of manufacturing process conditions used for the preparation of samples to be used in tensile test No. 5.

Table 5: manufacturing process conditions used for preparing the samples for tensile test No. 5.

minutes for inducing cross-linking

6. Processing the material in a press that is operated at

high temperature and pressure

7. 50% of weft fibers are parallel to the longitudinal direction of

the sample.

35 1. Immersing fabric in Octyltrimethoxysilane for 20 hours

2. Immersing in 5% acetic acid for 12 hours.

3. 2% catalyst

4. Cooled monomer - good wetting

5. 9 fabric layers.

6. Curing temperature of 120°C for 60

minutes for inducing cross-linking

7. Processing the material in a press that is operated at

high temperature and pressure

8. weft fibers are parallel to the longitudinal direction of

the sample.

Reference is now made to Fig. 9 which is a bar graph illustration of the results of tensile test No. 5 according to embodiments of the invention.

Based on the results, the inventors concluded that "post curing" treatment made the sample tougher.

Sample 33 which was treated with acetic acid turned to be tougher than sample 31 (of tensile test No. 4). However, it should be noted that a 4% catalyst solution was used in the production process of sample 33 compared to a 2% catalyst solution which was used in the production process of sample 31.

Reference is now made to Fig. 10 which is a bar graph illustration of the results of tensile tests No. 5 and 6 according to embodiments of the invention.

As seen in the bar graph of Fig. 10, sample 35 seemed to be tougher than sample 32 (of tensile test No. 4). This is most likely due to the use of 9 fabric layers in sample 35 as opposed to the 8 layers of sample 32. In addition, the Young's modulus seemed to increase as the number of layers in a sample increased. The energy at break, however, was kept unchanged regardless of the number of layers in a sample.

It should be noted that increasing the number of fabric layers in a sample increased the sample's weight per unit area. Therefore, the inventors considered ways of optimizing the toughness of a sample while keeping its weight reasonably low.

TENSILE TEST No. 6

[0074] Table 6 provides a brief description of manufacturing process conditions used preparation of samples to be used in tensile test No. 6.

Table 6: manufacturing process conditions used for preparing the samples for tensile test No. 6.

is operated at high temperature and

pressure

6. 50% of weft fibers are parallel to the

longitudinal direction of the sample.

42 1. Immersing fabric in Octyltrimethoxysilane for 19 hours

2. Immersing fabric in 5% acetic acid for 12 hours

3. 2% catalyst (new)

4. Cooled monomer - good wetting

5. 8 fabric layers.

6 Curing temperature of 120°C for 60

minutes for inducing cross-linking

7. Processing the material in a press that

is operated at high temperature and pressure

8. 50% of weft fibers are parallel to the

longitudinal direction of the sample.

PDCPD/Kevlai-49 C12 1. 2% catalyst (new)

2. Curing temperature of 60°C for

60 minutes for inducing cross-linking

C13 1. 2% catalyst (new)

2. Curing temperature of 60°C for

60 minutes for inducing cross-linking

3. Post curing at a temperature of 175°C for 10 minutes

C14 1. 1% catalyst (new)

2. Curing temperature of 60°C for

60 minutes for inducing cross

linking C15 1. 0.5% catalyst (new)

2. Curing temperature of 60°C for

60 minutes for inducing cross

linking

C16 1. 3% catalyst (new)

2. Curing temperature of 60°C for

60 minutes for inducing cross-linking.

[0075] Reference is now made to Fig. 11 which is a bar graph illustration of the results of tensile test No. 6 according to embodiments of the invention.

Based on the results, the inventors concluded:

1. The Young's modulus of PDCPD samples without fibers seemed to increase with an increase in the catalyst concentration.

2. Sample CI 4 seemed to absorb more energy and to possess a relatively high stress although the use of a 1% catalyst. Sample C14 may be able to absorb a relatively high amount of energy probably due to its relatively high elongation capability.

3. Energy absorption capability increased as the catalyst concentration decreased down to 1%. However, when the catalyst concentration was lower than 1%, the energy absorbed at break decreased in spite of the increase in elongation.

4. Post curing treatment decreased the Young's modulus and the energy absorption capability of a sample.

5. The properties of a sample that was treated with the new catalyst were further improved when treated with an acetic acid.

6. The octyltrimethoxysilane slightly improved the properties of the samples.

7. The new catalyst increased the mechanical properties of PDCPD samples without fibers. However, it did not improve the properties of a composite material. Specifically, it did not improve the properties of composite materials which were treated with acetic acid.

[0076] Reference is now made to Fig. 12 which illustrates a curve of breaking energy versus percent concentration of a catalyst and a curve of Young's modulus versus percent concentration of a catalyst according to embodiments of the invention. [0077] As seen in Fig. 12, an increase in the catalyst concentration increased the degree of cross-linldng and the value of the Young's modulus of a sample. As also seen, the energy did not decrease as the Young's modulus increased but instead reached a maximum (see the apex) at a point corresponding to a catalyst concentration of 1%. The energy kept increasing as the catalyst concentration increased up to 3%. It is possible that the excess of the catalyst caused plasticization.

TENSILE TEST No. 7

[0078] Table 7 provides a brief description of manufacturing process conditions used for the preparation of samples to be used in tensile test No. 7.

Table 7: manufacturing process conditions used for preparing the samples for tensile test No. 7.

8. Post curing at a temperature of 145°C for 60 minutes

1. Immersing fabric in a 5% acetic acid for an hour

2. 2% catalyst (new)

3. Good wetting

4. 8 fabric layers

5. Curing temperature of

120°C for 60 minutes for inducing cross-linldng

6. 8 tons hot press

7. Processing the material in a Press

in such a way that the weft fibers are parallel to the longitudinal direction of the sample.

1. Immersing fabric in a 5% acetic acid for an hour

2. 2.5% catalyst (new)

3. Good wetting

4. 8 fabric layers

5. Curing temperature of

120°C for 60 minutes for inducing cross-linking

6. 8 tons hot press

7. the weft fibers are parallel to the

longitudinal direction of the sample.

8. Post curing at a temperature of 145°C for 60 minutes

1. Immersing fabric in a 5% acetic acid for an hour

2. 0.5% catalyst (new)

3. Good wetting

4. 8 fabric layers

5. Curing temperature of 120°C for 60 minutes for inducing cross- linking

6. 8 tons hot press

7. The weft fibers are parallel to the longitudinal direction of the

sample. Post curing at a temperature of 145°C for 60 minutes

Reference is now made to Fig. 13 which is a bar graph illustration of the results of tensile test No. 7 according to embodiments of the invention.

[0079] Based on results, the inventors concluded the following:

1. Considering the fact that all weft fibers were parallel to the longitudinal direction of the sample, the Young's modulus value was expected to increase. However, compared to samples 16 and 17 of tensile test No. 4, the Young's modulus value of the current samples seemed to decrease. This may be due to deterioration in the catalyst's activity and/or due to the use of a new fabric material.

2. As seen in previous tests, the use of acetic acid improved the mechanical properties of the sample.

3. Post curing treatment increased the Young's modulus of a sample.

4. The mechanical properties of a sample seemed to deteriorate when a 0.5% catalyst solution was used instead of a 2% catalyst solution.

TENSILE TEST No. 8

[0080] Additional tensile tests were to be conducted in order to determine why the Young's modulus decreased in tensile test No. 7 and for examining the dependency of the sample's mechanical properties on the concentration of the new catalyst.

[0081] Table 8 provides a brief description of manufacturing process conditions used for the preparation of samples to be used in tensile test No. 8.

Table 8: manufacturing process conditions used for preparing the samples for tensile test No.

8.

. Processing the material in a press

in such a way that the weft fibers are parallel to the longitudinal direction of the sample.

1. Immersing fabric in a 0.5% acetic acid for an hour

2. 2% catalyst (new)

3. Good wetting - 8 layers

4. Curing temperature of

120°C for 60 minutes for inducing cross-linking

5. 8 tons hot press

. Processing the material in a press

in such a way that the weft fibers are parallel to the longitudinal direction of the sample

. Post curing at a temperature of 145°C for 60 minutes

1. Immersing fabric in a 5% acetic acid for an hour

2. 0.75% catalyst (new)

3. Good wetting; 8 layers

4. Curing temperature of

120°C for 60 minutes for inducing cross-linking

5. 8 tons hot press

. Processing the material in a press

in such a way that the weft fibers are parallel to the longitudinal direction of the sample

. Post curing at a temperature of 145°C for 60 minutes

1. Immersing fabric in acetone for 24 hours

2. Immersing in a 5% acetic acid for an hour

3. 2% catalyst (new)

4. Good wetting - 8 layers

5. Curing temperature of

120°C for 60 minutes for inducing cross-linking

6. 8 tons hot press [0082] Table 9 illustrates the relationship between the catalyst concentration and the mechanical properties of the samples during tensile tests.

Table 9: Relationship between the catalyst concentration and the mechanical properties of the samples during tensile tests.

[0083] Reference is now made to Fig. 14 which illustrates curves of mechanical properties of samples kept under tensile stress versus percent concentration of a catalyst according to embodiments of the invention.

Based on Table 9 and Fig. 14, the inventors concluded that:

1. The Young's modulus of a sample increased as the catalyst concentration increased.

As seen in the plot, the increase in toughness was maximal when the catalyst concentration was between 0.5% and 0.75%. Similarly, when the catalyst concentration was between 2% and 2.5%, the increase in toughness was minimal.

2. Stress seemed to reach its highest value when the catalyst concentration was 0.75%.

A higher catalyst concentration lead to a decrease in the stress and a catalyst concentration between 2% to 2.5% lead to the steepest decrease in the stress.

3. The energy was highest when the catalyst concentration was 0.75%.

4. The highest degree of elongation was achieved when a 2.5% catalyst solution was used.

[0084] Based on the above results, it seemed that in order to optimize the mechanical properties of a sample, a catalyst concentration should be lower than 2%. In addition, the inventors compared the mechanical properties of sample 52 which was made of a "new" fabric (with no post curing treatment) to the mechanical properties of the following samples:

(a) a sample which was made of an "old" fabric and was processed with same processing conditions;

(b) a sample made of a "new fabric" which was immersed in a solvent such as, for instance, an acetone to remove surface active contaminants.

The results of this test are given in plot 11.

Reference is now made to Fig. 15 which is a bar graph illustration of mechanical properties of samples made of various types of fabrics kept under tensile stress according to embodiments of the invention.

[0085] As seen, samples made of an "old" fabric produced the highest Young's modulus which was slightly smaller than the Young's modulus of previous samples (sample 32 of tensile test set 4). However, the removal of surface active contaminants from the "new" fabric seemed to improve the Young's modulus of the samples, and to increase the amount of energy absorbed at break and the maximal stress tolerated by the samples prior to breaking. Based on the observed results, the inventors concluded that the "old" catalyst probably did not "age" (as previously assumed). Instead, it was the removal of surface active contaminants from the fabric that improved the mechanical properties of the samples.

FLEXURAL TESTS

[0086] In order to emulate the forces active in ballistic tests, the inventors conducted a set of flexural tests. The active forces in both flexural tests and ballistic tests may include a tensile stress, a pressing force and a scissoring force. However, ballistic tests involve with velocities that are significantly higher than the velocities of flexural tests.

FLEXURAL TEST No. 1

[0087] Table 10 provides a brief description of manufacturing process conditions used for the preparation of samples to be used in flexural test No. 1.

Table 10: manufacturing process conditions used for preparing samples to be used in flexural test No. 1 1. Immersing fabric in a 2% Vinylsilane

. 2% fresh catalyst

3. Good wetting

4. 8 layers

5. Curing temperature of

120°C for 60 minutes for inducing cross-linldng

1. Immersing fabric in a 5% acetic acid

2. 2% catalyst

3. Low pressure

4. 8 layers

5. Curing temperature of

120°C for 60 minutes for inducing cross-linldng

1. Immersing fabric in a 5% acetic acid

2. 2% catalyst

3. Cooled monomer

4. 8 tons hot press

5. 8 layers

6. Curing temperature of

120°C for 60 minutes for inducing cross-linldng

1. Immersing fabric in 1 % Vinylsilane

2. 2% catalyst

3. Cooled monomer

4. 8 tons hot press

5. 8 layers

6. Curing temperature of

120°C for 60 minutes for inducing cross-linldng

1. Immersing fabric in 5% acetic acid

2. 2% catalyst

3. Cooled monomer and good wetting

4. 8 tons hot press

5. 8 layers

6. Curing temperature of 120°C for 60 minutes for inducing cross-linking

14 1. Immersing fabric in 5% acetic acid

2. 2% catalyst

3. Cooled monomer and good wetting

4. 8 tons hot press

5. 8 layers

6. Curing temperature of

150°C for 60 minutes for inducing cross-linking

15 1. Immersing fabric in 1 % Vinylsilane

2. 2% catalyst

3. Cooled monomer and good wetting

4. 8 tons hot press

5. layers

6. Curing temperature of

150°C for 60 minutes for inducing cross-linking

Old Data 1. 2% catalyst

2. Curing temperature of

70°C for 60 minutes for inducing cross-linking

[0088] Reference is now made to Fig. 16 which is a bar graph illustration of the results of flexural test No. 1 according to embodiments of the invention.

Based on the results, the inventors concluded:

1. Vinylsilane did not improve the mechanical properties of the samples.

2. Acetic acid improved the mechanical properties of the samples.

3. Lower processing pressure lead to a more concentrated matrix which most likely lead to a lower Young's modulus.

4. Good wetting improved the mechanical properties of the samples.

5. The Young's modulus of sample 15 was significantly high. This may be due to the direction of the fibers in the sample (this phenomenon was also observed in tensile test no. 2). Keeping a relatively high curing temperature for inducing cross-linking, increased the Young's modulus. The Young's modulus increased most likely as a result of an increase in the degree of cross-linking.

Acetic acid, good wetting and a specific fiber direction all improved the mechanical properties of samples.

FLEXURAL TEST No. 2

[0089] Table 1 1 provides a brief description of manufacturing process conditions used for improving the mechanical properties of samples which were to be used in flexural test No. 2. Table 1 1 : manufacturing process conditions used for preparing samples to be used in flexural test No. 2

Reference is now made to Fig. 17 which is a bar graph illustration of the results of flexural test No. 2 according to embodiments of the invention.

[0090] Just like in the tensile tests, the Young's modulus values of samples 16 and 17 were similar to each other in the flexural test as well. In addition, the maximal stress and the

Young's modulus of sample 18 seemed to be relatively low and even lower than the corresponding values which were obtained in flexural tests set no. 1. This may be due to the use of a relatively high curing temperature for inducing cross-linking which may lead to degradation of the samples.

[0091] In addition, the maximal stress of samples 16 and 17 seemed to be similar and much higher than the maximal stress of sample 18. This may be due to the arrangement of the fibers in the sample.

FLEXURAL TEST No. 3

[0092] Whether the warp or the weft fibers were to be directed parallel to the longitudinal direction of the sample might affect the properties of the sample. To test this, two types of samples were tested alternately, i.e., one sample with warp fibers that are arranged parallel to the longitudinal direction of the sample, and another sample with weft fibers that are arranged parallel to the longitudinal direction of the sample.

It should be noted that all samples were surface treated with octyltrimethoxysilane.

Table 12 provides a brief description of manufacturing process conditions used for improving the mechanical properties of samples which were to be used in flexural test No.4.

Table 12: manufacturing process conditions used for preparing samples to be used in flexural test No. 3

38 1. Immersing fabric in Octyltrimethoxysilane for 12 hours

2. Immersing in 5% acetic acid for an hour

3. 2% catalyst

4. Cooled monomer B - good wetting

5. High pressure

6. 8 layers

7. Curing temperature of 120°C for 60

minutes for inducing cross-linking

8. 50% of weft fibers are parallel to the longitudinal

direction of the sample.

Reference is now made to Fig. 18 which is a bar graph illustration of the results of flexural test No. 4 according to embodiments of the invention.

[0093] The inventors found that the maximal stress tolerated by sample 17 prior to breaking and its Young's modulus were higher than the maximal stress tolerated by sample 38 prior to breaking and its Young's modulus.

[0094] The properties of sample 38 seemed to be similar to the properties of some samples tested in flexural tests no. 1 and 2. In those samples, the weft fibers were parallel to the latitude direction of the sample. Thus, it was expected that the flexural test results produced with sample 38 (in which 50% of the weft fibers were parallel to the longitudinal direction of the sample) would fall between the results produced with sample 17 and the results produced in previous flexural tests no. 1 and 2. However, the results were found to be closer to the results of flexural tests no. 1 and 2. Therefore, it was concluded that the concentration of weft fibers which were to be arranged parallel to the longitudinal direction of a sample had to be significantly high (i.e., higher than 50%) in order to improve the properties of the sample.

DSC tests

[0095] Conducting DSC tests on samples which have different glass transition temperatures (T _g ) may aid in understanding the reaction process and in determining the extent of reaction. It is assumed that T _g increased as the degree of cross-linking in a sample increased, therefore, samples having different mechanical properties were DSC tested. DSC TEST No. 1

[0096] In order to determine processing conditions which may induce the desired degree of cross-linking, the inventors conducted some DSC tests.

Table 13 provides a brief description of manufacturing process conditions of samples which were to be used in DSC test No.1.

Table 13: manufacturing process conditions used for preparing samples to be used in DSC test No. 1

2. Curing temperature of 150°C for 60 minutes for inducing cross-linking

Prior 1. 2% catalyst

work 2. Curing temperature of 70°C for 60 minutes for inducing cross-linking

[0097] Reference is now made to Fig. 19 which is a bar graph illustration of the results of DSC test No. 1 according to embodiments of the invention.

Based on the results, the inventors concluded that:

1. An increase in the catalyst concentration may increase T _g and may improve the mechanical properties of a sample.

2. Samples tested in previous work were found to have T _g values which were greater than T _g values of current samples. This may be due to an aging catalyst.

3. The T _g value of composite samples and mainly those composite samples which were treated with vinylsilane was lower. This may confirm the possibility of catalyst "poisioning".

DSC TEST No. 2

[0098] To examine the extent of reaction obtainable with the new catalyst, DSC tests were performed on samples which were treated with the new catalyst.

Table 14 provides a brief description of manufacturing process conditions of samples which were to be used in DSC test No .2.

Table 14 manufacturing process conditions used for preparing samples to be used in DSC test No. 2

(without fibers) 2. Curing temperature of 70°C for 60

aging minutes for inducing cross-linking (Approx.)

PDCPD (2%) 1. 2% catalyst

(new) 2. Curing temperature of 120°C for 60

minutes for inducing cross-linking

Reference is now made to Fig. 20 which is a bar graph illustration of the results of DSC test No. 2 according to embodiments of the invention.

[0099] The inventors found that the degree of cross-linking was higher in samples which were undergoing an "aging" process (i.e., samples which were kept unused for a predefined period of time). In addition, based on the fact that the "new" catalyst improved the properties of the samples, the inventors concluded that it was possible that the "old" catalyst was not efficient anymore.

[00100] Reference is now made to Fig. 21 which is an optical image illustrating surface morphology of a sample treated with a "new" catalyst according to embodiments of the invention.

As seen in the image presented in Fig. 21, hydrates seemed to form at the surface of the sample. This was most likely due to the relatively high processing temperature and also due to an "aggressive activity" of the "new" catalyst.

[00101] It should be noted that hydrates may negatively affect the adhesion of the matrix to the fibers. Therefore, in order to avoid the formation of hydrates at the surface of samples, a curing temperature of 60°C was used in the production process of samples containing a PDCPD without fibers-type matrix.

DSC TEST No. 3

[00102] In order to get some information regarding the "post curing" process and its effect on T _g and on the degree of cross-linking in a sample, DSC tests were performed on samples containing PDCPD (with and without fibers) which were processed using two heating cycles. Table 15 provides a brief description of manufacturing process conditions of samples which were to be used in DSC test No.3. Table 15 manufacturing process conditions used for preparing samples to be used in DSC test No. 3

[00103] Reference is now made to Fig. 22 which is a bar graph illustration of the results of DSC test No. 3 according to embodiments of the invention.

Based on the results, the inventors concluded that:

1. Higher processing temperatures may induce an increase in the T _g value of a sample in a first heating cycle but may induce a decrease in the T _g value of a sample in a second heating cycle. This may be due to a degradation of the sample which may be occurring during the second heating cycle. In addition, "post curing" treatment may increase the degree of cross- linking.

2. In contrast to item 1, "post curing" treatment may improve the properties of PDCPD/Kevlar49-based samples only in the second heating cycle.

DSC TEST No. 4

[00104] To determine what caused the mechanical properties of samples (of tensile test No. 7) to deteriorate, additional DSC tests were carried out.

[00105] Table 16 provides a brief description of manufacturing process conditions of samples which were to be used in DSC test No.4.

Table 16 manufacturing process conditions used for preparing samples to be used in DSC test No. 4

linking

6. 100% of weft fibers are parallel to the longitudinal direction of the sample.

. Post curing at a temperature of 145°C for 60 minutes

1. Immersing fabric in 5% acetic acid for an hour

2. 2% catalyst (new)

3. Cooled monomer - good wetting

4. 8 tons hot press

5. Curing temperature of 120°C for 60 minutes for inducing cross- linking

6. 100% of weft fibers are parallel to the longitudinal direction of the sample.

1. Immersing fabric in 5% acetic acid for an hour

2. 2.5% catalyst (new)

3. Cooled monomer - good wetting

4. 8 tons hot press

5. Curing temperature of 120°C for 60 minutes for inducing cross- linking

6. 100% of weft fibers are parallel to the longitudinal direction of the sample.

7. Post curing at a temperature of 1 5°C for 60 minutes

1. Immersing fabric in 5% acetic acid for an hour

2. 0.5% catalyst (new)

3. Cooled monomer - good wetting

4. 8 tons hot press

5. Curing temperature of 120°C for 60 minutes for inducing cross- linking

6. 100% of weft fibers are parallel to the longitudinal direction of the sample.

7. Post curing at a temperature of 145°C for 60 minutes Reference is now made to Fig. 23 which is a bar graph illustration of the results of DSC test No. 4 according to embodiments of the invention.

As seen in the plot of Fig. 23, the first and the second heating cycles were not related in any way. [00106] In addition, although similar processing conditions were used for processing sample 40 of DSC test No. 3 and sample 52 of the cun-ent test set, the results obtained with sample 40 of DSC test No. 3 seemed to be better than the results obtained with sample 52 of the current test set. DMA TESTS

[00107] DMA TEST No. 1

Table 17 provides a brief description of manufacturing process conditions of samples which were to be used in DMA test No.1.

Table 17 manufacturing process conditions used for preparing samples to be used in DMA test No. 1

Reference is now made to Fig. 24 which is a bar graph illustration of the results of DMA test No. 1 according to embodiments of the invention.

Based on the results, the inventors concluded:

1. T _g increased and the degree of cross-linking improved with an increase in the catalyst concentration. 2. The catalyst activity was found to be lower than what it used to be in previous work. The decrease in the catalyst's activity was also reflected in the mechanical and in the DSC tests. DMA TEST No. 2

[00108] In order to compare DSC test results to DMA test results, DMA tests were also performed on samples which were produced with the new catalyst. In addition, various concentrations of the catalyst were examined in order to test the effect of the catalyst concentration on T _g and on the storage modulus.

Table 18 provides a brief description of manufacturing process conditions of samples which were to be used in DMA test No. 2.

Table 18 manufacturing process conditions used for preparing samples to be used in DMA test No. 2.

[00109] Reference is now made to Fig. 25 which illustrates a curve of (T _g ) versus percent concentration of the catalyst according to embodiments of the invention.

Based on the observed in the above table and Fig. 25, the inventors concluded:

1. An increase in the catalyst concentration increased the T _g value of a sample and the degree of cross-linking in a sample. A catalyst concentration that was significantly high (i.e., 3%) induced plasticization. 2. Relatively lower processing temperature may increase the T _g value of a sample. It might be that a too high processing temperature may induce a non-uniform cross-linking process and even degradation.

Reference is now made to Fig. 26 which illustrates curves of storage modulus versus percent concentration of the catalyst according to embodiments of the invention.

As seen in Fig. 26, the inventors further concluded that

1. At a temperature of 25°C, storage modulus increased as the catalyst concentration increased (except when the catalyst concentration was 0.5%).

4. At a temperature of 75°C, storage modulus increased as the catalyst concentration increased. However, at a catalyst concentration of about 3%, storage modulus seemed to decrease most likely due to plasticization,

Ballistic TESTS

[00110] Several sets of ballistic tests were performed.

1. The first set was intended for understanding the testing conditions and for determining the type of samples required for such tests.

2. The various tests and specifically the DMA and the DSC tests showed that the catalyst which was used in the first set of ballistic tests "aged" and had to be replaced.

3. Since previously made samples possessed various weights per unit area, the inventors aimed at producing samples with substantially identical weight per unit area.

4. Based on the ballistic tests results, new and improved samples were produced.

Ballistic TEST No. 1

[00111] Ballistic test No. 1 was performed on samples made of PDCPD/Kevlar49.

Table 19 provides a brief description of manufacturing process conditions of samples which were to be used in ballistic test No. 1.

Table 19 manufacturing process conditions used for preparing samples to be used in ballistic test No. 1.

[min]

Drying temperature 120

(from acid)

[°C]

No. of fabric layers 24

Volumetric Fiber cone. 66

[%]

Time of Press 60 (after heating)

[min]

Press Temperature 120

[°C]

Press Pressure 7.8

[Mpa

Catalyst Concentration 2

[%] (new) (old

catalyst)

Balistic Test Result 2452

(ft/sec)

[00112] Since the flight velocity of the hitting projectile approached an upper limit value, the inventors concluded that further improvements in the ballistic test results might prevent the hitting projectile from passing through the element being hit. Therefore, they decided to decrease the number of fabric layers from 24 layers to 18 layers in both the PDCPD and the epoxy matrices.

[00113] In addition, since only PDCPD/Kevlar49 type samples were used in this test, it was not possible to compare the results obtained with one matrix to results obtained with another. However, a visualization examination of the sample lead to the following observations:

1. When a hitting projectile hit a sample, it first hit its surface and caused the extraction of fibers from that surface in a direction opposite to the flight direction of the hitting projectile. This way, energy was absorbed by the sample. 2. The hitting projectile caused the extraction of fibers also from a surface through which it left the sample. In this case, the extraction of fibers occured along the flight direction of the hitting projectile.

3. The hitting projectile caused the surface from which it left the sample to blow up. This phenomenon caused delamination, i.e., separation of the fabric layers. This phenomenon might also caused a change in the breaking mechanism, i.e., from a breaking mechanism which was governed via shear to a breaking mechanism which was governed via tension and distortion (and which probably required a greater amount of energy).

[001 14] Reference is now made to Fig. 27 which is an optical image illustrating a surface of a sample through which a projectile has passed in ballistic test No. 1 according to embodiments of the invention.

Ballistic TEST No. 2

[00115] A second set of ballistic tests was earned out with Epoxy/Kevlar49 samples. The two samples as well as their production processes were substantially identical except for an additional vacuuming stage which was included in the production process of one of the samples in order to reduce the formation of air bubbles in that sample during processing.

[00116] As noted earlier, based on the results of the first ballistic test, the inventors decided to decrease the number of fabric layers in a sample from 24 to 18 layers. In addition, it should be noted that based on mechanical test results as described earlier, samples were prepared in such a way that the weft fibers were arranged to be parallel to the longitudinal direction of the sample. It should be noted, however, that similar results were to be expected with samples in which the weft fibers were to be arranged parallel to the latitude direction of the sample since the flight direction of a projectile was parallel to the surface normal of the surface. However, the ballistic test results might have been different if the sample was produced in such a way that the weft fibers were parallel to the surface normal as opposed to the longitudinal direction of the sample.

[00117] Table 20 provides a brief description of manufacturing process conditions of samples which were to be used in ballistic test No. 2.

Table 20 manufacturing process conditions used for preparing samples to be used in ballistic test No. 2. Sample Bep 1 Bep 2

Epoxy DOE: DOE:

Base A D.E.R D.E.R

331 331

Epoxy ISQ ISQ

Hardener B FP148 FP148

A Cone. 66.7 66.7

[%]

B Cone. 33.3 33.3

[%]

Volumetric 67 68

Cone, of

the fibers

Press Time 72 44

[hour

Press Temp. 18-25 18-25

[°C]

Vaccum 1

Time

[hour

Post 1 1 1 1 1 1

Curing

Time

[hour]

Temp. Post 50 60 70 50 60 70

curing

PC]

[00118] It should be noted that a production process which was to include a press time of 24 hours and a post curing treatment was preferred when making epoxy matrices. Reference is now made to Fig. 28 which is a bar graph illustration of the results of ballistic test No. 2 according to embodiments of the invention.

Based on the results, the inventors concluded that:

1. Using a vacuum pump for decreasing the amount of air bubbles in a sample, thus, for decreasing the relative fiber concentration in a sample did not seem to be efficient. The inventors noticed that the fiber concentration turned to be actually lower in samples that were manufactured without the use of a vacuum pump.

2. The inventors noticed that Bepl whose production process did not include vacuuming produced better results than Bep 2 whose production process included vacuuming. Thus, ballistic test results seemed to be compatible with fiber concentration of the samples, i.e., samples having a higher fiber concentration produced better test results.

In addition to the ballistic tests, the samples were visually tested.

[00119] Reference is now made to Fig. 29 which is an optical image illustrating a surface of a sample which was hit by a projectile. As seen, fibers were extracted from the surface of the sample as a result of the hit.

[00120] Reference is now made to Fig. 30 which is an optical image illustrating various color shaded-surface through which a projectile has left a sample.

Based on the observed in the images shown in Fig. 30, the inventors concluded:

1. Fiber extraction seemed similar in surfaces which were hit by a projectile and in surfaces from which the projectile has been ejected.

2. Blow ups occurring at surfaces of samples made with a PDCPD matrix seemed to be more pronounced than blow ups occurring at surfaces of samples made with an epoxyjnatrix. This may indicate that the shear mode governed breakage in samples made with an epoxy matrix.

3. Color variations at various locations across the surface of a sample made with an epoxy matrix might have indicated that the surface might have been undergoing delamination.

Ballistic TEST No. 3

[00121] In order to compare the PDCPD/Kevlar49 samples to the Epoxy/Kevlar49 samples, the inventors prepared four PDCPD Kevlar49 samples all with 18 fabric layers for ballistic tests. Table 21 provides a brief description of manufacturing process conditions of samples which were to be used in ballistic test No. 3.

Table 21 manufacturing process conditions used for preparing samples to be used in ballistic test No. 3.

Reference is now made to Fig. 31 which is a bar graph illustration of the results of ballistic test No. 3 according to embodiments of the invention.

[00122] Based on the results, the inventors concluded that the ballistic test results were improved when conventional type matrices were replaced with PDCPD matrices. In addition, despite the fact that the best ballistic test result was obtained with sample B2, and the lowest test result was obtained with sample B3, ballistic test results were not found to depend on the fiber concentration in a sample.

[00123] In addition, the use of acetic acid as well as the use of octyltrimethoxysilane were found to improve the ballistic test results. Similarly, a decrease in the catalyst concentration down to 1 % also improved the test results.

Reference is now made to Fig. 32 which is an optical image illustrating multiple blown up regions of a surface from which projectiles have ejected according to embodiments of the invention.

[00124] Reference is now made to Fig. 33 which is an optical image illustrating various color shaded-surface from which projectiles have ejected according to embodiments of the invention.

Based on the images presented in Figs 32-33, the inventors concluded that:

1. A projectile caused the extraction of fibers out of a surface through which it penetrated the sample and from a surface from which it was ejected.

2. Significant blow ups at various locations across the surface from which projectiles were ejected have been observed.

3. Color variations across a surface of a sample which has been hit were first observed in the 2 ^nd ballistic test with an epoxy matrix. Such color variations were also observed in this test mainly with sample B5 which was produced with a catalyst having a concentration lower than 50%.

Ballistic TEST No. 4

[00125] Five PDCPD samples and one epoxy sample were used in the fourth ballistic test. This test was intended to improve ballistic test results which were previously obtained. In addition, since tests results obtained with samples made of PDCPD/Kevlar49 were higher than tests results obtained with Epoxy/Kevlar49 in the 3rd set of tests, the inventors aimed at preparing PDCPD/Kevlar49 and Epoxy/Kevlar49 samples with comparable weight per unit area and with comparable fiber concentration in order to be able to compare the two samples. Table 22 provides a brief description of manufacturing process conditions of samples which were to be used in ballistic test No. 4.

Table 22 manufacturing process conditions used for preparing samples to be used in ballistic test No. 4.

the fibers

[%]

Weight 11.1 11.4 10.7 10.7 10.8 11.3 Per area

Kg/m ²

Ballistic 2071 2026 2248 2150 2026 1910 test

results

Improv. 8.4 6.1 17.7 12.6 6.1

[%]

Improv. 10.4 5.1 24.3 18.9 11.0

Compared

to weight

Per area

[%]

[00126] Reference is now made to Fig. 34 which is a bar graph illustration of the results of ballistic test No. 4 according to embodiments of the invention.

Based on the results, the inventors concluded that:

1. The use of PDCPD/Kevlar49 produced better ballistic test results than Epoxy/Kevlar49.

2. Current tests with Epoxy/Kevlar49 produced results which were better then the results obtained in the 3 ^rd set of tests.

3. Ballistic test results that were obtained with B9 and B 10 were significantly different than the results obtained with the epoxy. In addition, the results obtained with sample B9 which did not undergo a "post curing" treatment were higher than the results obtained with sample B10 (which has undergone a "post curing" treatment). Finally, ballistic test results which were obtained with samples containing a PDCPD matrix were higher by approximately 17.7% than the test results which were obtained with samples containing an epoxy matrix. 4. Ballistic test results were not necessarily dependent on the fiber concentration in a sample. B8, for instance, had the lowest fiber concentration but did not produce the lowest ballistic test results.

5. B9 which produced the highest ballistic test results had the lowest weight per unit area. In contrast, Bep3 which consisted an epoxy matrix had a relatively high weight per unit area. Therefore, the inventors concluded that samples with a PDCPD matrix might be lighter than samples having an epoxy matrix by more than 24%.

6. After the ballistic test, samples were undergoing a visual examination. The blowing phenomenon was mostly significant in samples B9 and BIO which also provided the best ballistic test results. The observed blowing phenomenon indicated that samples B9 and BIO were both highly flexible, thus, enabled the activation of tensile forces rather than shear forces upon breakage. MICROSCOPY TEST RESULTS

[00127] Reference is now made to Figs. 35A-35C which are optical microscopy images, each illustrating a surface profile of a surface from which a projectile has ejected according to embodiments of the invention.

[00128] Samples were cut close to the region through which a projectile has penetrated the sample. An optical microscopy image of the cut was produced and analyzed. Figs. 35A-35C illustrate cuts in three different samples, i.e., B9, B8, and Bep3 respectively. As seen in these images, B9 which included a PDCPD matrix and was produced with a catalyst concentration of about 0.5% seemed to possess the highest degree of delamination, i.e., higher than B8 which included a PDCPD matrix and was produced with a catalyst concentration of about 2% and which seemed to contain gaps between its layers (seen in image 34B) and higher than Bep3 which was made of an epoxy matrix.

[00129] The fact that B9 seemed to possess the highest degree of delamination may aid in explaining the fact that a high amount of energy was being absorbed by the sample and caused tensile forces and elongation to govern breakage, and thus, caused to high ballistic test results.

[00130] Based on the above tests and analyses, the inventors concluded the following: 1. PDCPD Kevlar49 samples produced ballistic test results which were higher by approximately 17.7% than test results that were produced with Epoxy/Kevlar49 samples.

2. In some cases, PDCPD/Kevlar49 samples with a weight per unit area which was smaller than the weight per unit area of Epoxy/Kevlar 49 samples by over 8.5% produced better ballistic test results than the Epoxy/Kevlar 49 samples.

3. A catalyst concentration of 0.5% produced the highest ballistic test results.

[00131] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.