Bulletproof composite material and preparation method thereof

Abstract

The invention discloses a bulletproof composite material and a preparation method thereof, and relates to the technical field of bulletproof composite materials. The bulletproof composite material is formed by compounding aramid fibers and a resin matrix, wherein the resin matrix comprises the following raw materials in parts by weight: 60-70 parts of epoxy resin, 5-8 parts of a modified toughening agent, 4-5 parts of a curing agent, 1-2 parts of a heat stabilizer, 1-2 parts of an inorganic filler, 0.5-1 part of a coupling agent and 2-5 parts of a wetting agent; the preparation method comprises the following steps: reacting cyanuric chloride with 4-hydroxyphenylboronic acid to generate an intermediate 1; reacting the intermediate 1 with 3-amino-1, 2-epoxypropane to generate an intermediate 2; reacting the intermediate 2 with cystamine to generate an intermediate 3, and reacting the intermediate 3 with dopamine to generate the modified toughening agent. The bulletproof composite material prepared by the invention has good ballistic protection performance, multiple impact resistance and self-repairing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of bullet-proof composite materials, and in particular to a bullet-proof composite material and a preparation method thereof. Background Art

[0002] Bulletproof composite materials are key materials in the fields of national defense and public security. Their core requirement is to achieve effective protection against high-speed projectiles while being lightweight. They are widely used in bulletproof vests, armored vehicles, security shields, and other scenarios. Traditional metal armor (such as steel and aluminum alloy) is difficult to meet the comprehensive requirements of modern protection for "high specific strength, impact resistance, and weather resistance" due to its high density and poor flexibility. High-performance fiber-reinforced resin-based composite materials have gradually become the mainstream of bulletproof materials due to their advantages such as low density and high tensile strength. However, the existing technology still has the following difficulties: (1) The resin matrix is ​​relatively brittle and has insufficient energy dissipation capacity. Traditional epoxy resin has a high cross-linking density and low elongation at break. It is prone to brittle fracture under high-speed bullet impact and cannot effectively absorb the impact kinetic energy, resulting in excessive concavity on the back of the composite material. (2) The interface between the fiber and the resin is weak, resulting in serious delamination failure. Aramid fiber has a smooth surface and strong chemical inertness. The interface bonding with the resin matrix mainly relies on physical adsorption, and the interlayer shear strength is relatively low. During impact, the fiber and the resin are prone to interface delamination, resulting in rapid crack expansion and poor resistance to multiple impacts. (3) Poor self-repair and weather resistance, and short service life. Current bulletproof composite materials lack certain self-repair properties. Microcracks generated by impact cannot be healed. After repeated use, the protective performance irreversibly declines, and the moisture and heat resistance performance needs to be improved. The above problems seriously limit the practical application of bulletproof composite materials.

[0003] Chinese invention patent publication number CN102604320A discloses a flexible, bullet-resistant composite material with a novel resin matrix and its processing method. This composite material, processed from this novel matrix resin, is pollution-free throughout the entire molding process, exhibits excellent aging and yellowing resistance, and exhibits minimal degradation of ballistic performance at elevated temperatures. However, its impact resistance and interfacial bonding properties are poor, and it lacks self-healing capabilities. Therefore, the development of a bullet-resistant composite material combining impact resistance, interfacial reinforcement, and self-healing capabilities is urgent. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a bulletproof composite material and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions: A bulletproof composite material is composed of aramid fiber and a resin matrix; the resin matrix includes the following raw materials in parts by weight: Epoxy resin: 60-70 parts; Modified toughening agent: 5-8 parts; Curing agent: 4-5 parts; Heat stabilizer: 1-2 parts; Inorganic filler: 1-2 parts; Coupling agent: 0.5-1 part; Wetting agent: 2-5 parts; The chemical structural formula of the modified toughening agent is as follows: .

[0006] The modified toughening agent is prepared by the following method: S1: Under nitrogen protection, cyanuric chloride, 4-hydroxyphenylboronic acid and anhydrous acetonitrile were mixed, triethylamine was added dropwise, and the reaction was carried out for 4-5 hours. After post-treatment, intermediate 1 was obtained; S2: Under nitrogen protection, mix intermediate 1, 3-amino-1,2-epoxypropane and anhydrous tetrahydrofuran (THF), add N,N-diisopropylethylamine, react for 10-12 hours, and post-treat to obtain intermediate 2; S3: Under nitrogen protection, intermediate 2, cystamine and anhydrous THF were mixed, N, N-diisopropylethylamine was added, and the reaction was carried out for 5-6 hours. After post-treatment, intermediate 3 was obtained; S4: Under nitrogen protection, the intermediate 3, dopamine and anhydrous DMF were mixed, reacted for 10-12 hours, and post-treated to obtain a modified toughening agent.

[0007] In step S1, the molar ratio of cyanuric chloride to 4-hydroxyphenylboric acid is 1:(1-1.2).

[0008] In step S2, the molar ratio of the intermediate 1 and 3-amino-1,2-epoxypropane is 1:(1.05-1.1).

[0009] In step S3, the molar ratio of the intermediate 2 to cystamine is (2.05-2.1):1.

[0010] In step S4, the molar ratio of the intermediate 3 to dopamine is 1:(2-2.1).

[0011] The thermal stabilizer is 2,6-di-tert-butyl-4-methylphenol; the coupling agent is KH-560 silane coupling agent; the wetting agent is polyether modified silicone oil; the curing agent is one of hexamethylenediamine, diethylenetriamine, and triethylenetetramine; the inorganic filler is one of nano-silica and nano-montmorillonite; the aramid fiber is Kevlar K129 fiber; and the epoxy resin is E51 epoxy resin.

[0012] A method for preparing a bullet-proof composite material comprises the following steps: S1: Add 60-70 parts by weight of epoxy resin and 200 parts by weight of N-methylpyrrolidone into a reactor, heat to 60°C, stir, add 5-8 parts by weight of a modified toughening agent, 1-2 parts by weight of a heat stabilizer, 0.5-1 parts by weight of a coupling agent, and 2-5 parts by weight of a wetting agent in sequence, stir for 20 minutes, then add 1-2 parts by weight of an inorganic filler, stir at 1500 rpm for 30 minutes, and finally add 4-5 parts by weight of a curing agent and stir for 20 hours to obtain a resin glue; S2: The aramid fiber was vacuum dried at 120°C for 2 hours, and then laid flat on the unwinding device of the impregnation machine. The resin glue was added to the resin tank. The fiber tension was set to 4-6 N / cm, the resin tank temperature was set to 60°C, and the impregnation speed was set to 1-2 m / min. The resin glue content was controlled to 50 wt% by a scraper. The impregnated fiber was then dried in a 50°C oven for 12 hours to obtain an aramid fiber / resin prepreg. S3: After the prepreg is laid alternately at [0° / 90°] 8, it is cut and placed in an autoclave for hot pressing to obtain a bulletproof composite material.

[0013] Due to the adoption of the above technical solution, the beneficial effects of the present invention include: (1) The phenylboronic acid in the modified toughening agent prepared by the present invention can form a borate bond with the fiber surface to dynamically build a structure, which first breaks reversibly under impact load to absorb energy; the disulfide bond then breaks and reorganizes through redox reaction, further absorbing energy; at the same time, the triazine ring (rigid core) undergoes bond angle deformation, absorbing additional energy. The synergistic effect of the three can increase the total energy absorption rate of the resin matrix, thereby significantly improving the ballistic limit of the composite material and effectively improving the ballistic performance of the bulletproof composite material. In addition, the dynamic bond (borate bond / disulfide bond) breaks first under impact to dissipate energy, while the triazine ring core maintains the integrity of the skeleton, achieving the characteristic of "local sacrificial bond breaking - overall structural integrity", thereby improving the fracture toughness of the composite material. At the same time, the presence of the dynamic bond significantly improves the self-healing performance of the bulletproof composite material.

[0014] (2) The polyhydroxy structure of the end-grafted dopamine of the modified toughening agent prepared by the present invention can form hydrogen bonds and π-π stacking with the amide groups on the surface of the aramid fiber, thereby strengthening the interfacial bonding between the fiber and the resin, effectively inhibiting the expansion of impact cracks along the interface, and improving the resistance of the bullet-proof composite material to multiple impacts. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the H NMR spectrum of the modified toughening agent prepared in Example 1. DETAILED DESCRIPTION

[0016] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0017] Example 1 Preparation of modified toughening agent: S1: In a reaction flask, add 0.1 mol of cyanuric chloride and 300 ml of anhydrous acetonitrile, protect with nitrogen, and stir for 30 minutes; dissolve 0.1 mol of 4-hydroxyphenylboronic acid in 300 ml of anhydrous acetonitrile, and add 0.12 mol of triethylamine to prepare a mixed solution; under an ice bath, slowly add the mixed solution dropwise to the reaction flask for 30 minutes, react at 0°C for 5 hours, filter after completion of the reaction, distill under reduced pressure at 50°C for 1.5 hours, recrystallize from 250 ml of anhydrous ether, filter, wash the filter cake with deionized water until neutral, and dry in vacuo at 40°C for 8 hours to obtain intermediate 1; the reaction equation is as follows: ; Its H-NMR spectrum data are as follows: 1 H NMR (500 MHz, Chloroform- d ) δ 7.46-7.41 (m, 2H), 7.32 (s, 2H), 6.58-6.52 (m, 2H).

[0018] S2: Under nitrogen, add 0.1 mol of intermediate 1 and 300 ml of anhydrous THF to a reaction flask and stir for 30 minutes. Dissolve 0.105 mol of 3-amino-1,2-epoxypropane in 300 ml of anhydrous THF and add 0.1 mol of N,N-diisopropylethylamine to prepare a mixed solution. Slowly add the mixed solution dropwise to the reaction flask under an ice bath for 30 minutes and react at 30°C for 12 hours. After the reaction, distill under reduced pressure at 40°C for 2 hours. Add 100 ml of 0.1 M hydrochloric acid, stir thoroughly, and filter. Wash the filter cake with deionized water until neutral and dry it under vacuum at 40°C for 8 hours to obtain intermediate 2. The reaction equation is as follows: ; Its H-NMR spectrum data are as follows: 1 H NMR (500 MHz, Chloroform-d) δ 7.47-7.41 (m, 2H), 7.32 (s, 2H), 6.58-6.52 (m, 2H), 6.35 (s, 1H), 3.94 (d, J = 12.4 Hz, 2H), 3.90-3.83 (m,1H), 2.90 (q, J = 5.0 Hz, 2H).

[0019] S3: Under nitrogen, add 0.205 mol of intermediate 2 and 350 ml of anhydrous THF to a reaction flask and stir for 30 minutes. Dissolve 0.1 mol of cystamine in 350 ml of anhydrous THF and add 0.21 mol of N,N-diisopropylethylamine to prepare a mixed solution. Slowly add the mixed solution dropwise to the reaction flask under an ice bath for 30 minutes and react at 60°C for 6 hours. After the reaction, distill under reduced pressure at 40°C for 2 hours. Add 100 ml of 0.1 M hydrochloric acid, stir thoroughly, and filter. Wash the filter cake with deionized water until neutral and dry it under vacuum at 50°C for 8 hours to obtain intermediate 3. The reaction equation is as follows: ; Its H-NMR spectrum data are as follows: 1 H NMR (500 MHz, Chloroform-d) δ 7.47-7.41 (m, 4H), 7.32 (s, 4H), 6.58-6.52 (m, 4H), 5.77 (s, 2H), 4.49-4.34 (m, 4H), 4.00 (s, 2H), 3.79 (s,4H), 3.05-2.85 (m, 8H).

[0020] S4: Under nitrogen protection, 500 ml of anhydrous DMF, 0.1 mol of intermediate 3 and 0.1 mol of triethylamine were added to the reaction flask and stirred for 30 min. Then, 0.01 mol of BHT was added and 300 ml of a DMF solution containing 0.2 mol of dopamine was slowly added dropwise for 30 min. The reaction was carried out at 70 °C in the dark for 12 h. The reaction solution was cooled in an ice bath and the pH was adjusted to 4 with 0.5 M HCl. The solution was purified by Sephadex LH-20 gel column chromatography (eluent: methanol / water). V / V =1:1), freeze-dried at -50℃ for 48h to obtain a modified toughening agent; the reaction equation is as follows: ; Its H-NMR spectrum data are as follows: 1H NMR (500 MHz, Chloroform-d) δ 7.47-7.41 (m, 4H), 7.32 (s, 4H), 6.70-6.64 (m, 4H), 6.62-6.52 (m, 6H), 6.22 (d, J = 79.5 Hz, 4H), 5.77 (s,2H), 4.17 (d, J = 2.4 Hz, 4H), 3.98 (d, J = 5.2 Hz, 2H), 3.79 (s, 4H), 3.47(d, J = 5.2 Hz, 2H), 3.41 (s, 2H), 3.05-2.74 (m, 16H).

[0021] Example 2 Preparation of modified toughening agent: S1: In a reaction flask, add 0.1 mol of cyanuric chloride and 300 ml of anhydrous acetonitrile, protect with nitrogen, and stir for 30 minutes; dissolve 0.11 mol of 4-hydroxyphenylboronic acid in 300 ml of anhydrous acetonitrile, and add 0.2 mol of triethylamine to prepare a mixed solution; under an ice bath, slowly add the mixed solution dropwise to the reaction flask for 30 minutes, react at 0°C for 5 hours, distill under reduced pressure at 50°C for 1.5 hours, recrystallize from 250 ml of anhydrous ether, filter, wash the filter cake with deionized water until neutral, and dry in vacuo at 40°C for 8 hours to obtain intermediate 1; S2: Under nitrogen protection, add 0.1 mol of intermediate 1 and 300 ml of anhydrous THF to a reaction flask and stir for 30 minutes; dissolve 0.108 mol of 3-amino-1,2-epoxypropane in 300 ml of anhydrous THF and add 0.1 mol of N,N-diisopropylethylamine to prepare a mixed solution; slowly add the mixed solution dropwise to the reaction flask under an ice bath for 30 minutes and react at 35°C for 11 hours. After the reaction, distill under reduced pressure at 40°C for 2 hours, add 100 ml of 0.1M hydrochloric acid, stir thoroughly, and filter. Wash the filter cake with deionized water until neutral and dry it under vacuum at 40°C for 8 hours to obtain intermediate 2. S3: Under nitrogen, add 0.208 mol of intermediate 2 and 350 ml of anhydrous THF to a reaction flask and stir for 30 minutes. Dissolve 0.1 mol of cystamine in 350 ml of anhydrous THF and add 0.21 mol of N,N-diisopropylethylamine to prepare a mixed solution. Slowly add the mixed solution dropwise to the reaction flask under an ice bath for 30 minutes and react at 65°C for 5.5 hours. After the reaction, distill under reduced pressure at 40°C for 2 hours, add 100 ml of 0.1 M hydrochloric acid, stir thoroughly, and filter. Wash the filter cake with deionized water until neutral and dry it in a vacuum at 50°C for 8 hours to obtain intermediate 3. S4: Under nitrogen protection, 500 ml of anhydrous DMF, 0.1 mol of intermediate 3, and 0.1 mol of triethylamine were added to the reaction flask and stirred for 30 min. Then, 0.01 mol of BHT was added and 300 ml of a DMF solution containing 0.205 mol of dopamine was slowly added dropwise for 30 min. The reaction was carried out at 75 °C in the dark for 11 h. The reaction solution was cooled in an ice bath and adjusted to pH 4 with 0.5 M HCl. The product was purified by Sephadex LH-20 gel column chromatography (eluent: methanol / water). V / V =1:1), and freeze-dried at -50 °C for 48 h to obtain a modified toughening agent.

[0022] Example 3 Preparation of modified toughening agent: S1: In a reaction flask, add 0.1 mol of cyanuric chloride and 300 ml of anhydrous acetonitrile, protect with nitrogen, and stir for 30 minutes; dissolve 0.12 mol of 4-hydroxyphenylboronic acid in 300 ml of anhydrous acetonitrile, and add 0.2 mol of triethylamine to prepare a mixed solution; under an ice bath, slowly add the mixed solution dropwise to the reaction flask for 30 minutes, react at 5°C for 4 hours, filter after completion of the reaction, distill under reduced pressure at 50°C for 1.5 hours, recrystallize from 250 ml of anhydrous ether, filter, wash the filter cake with deionized water until neutral, and dry in vacuo at 40°C for 8 hours to obtain intermediate 1; S2: Under nitrogen protection, add 0.1 mol of intermediate 1 and 300 ml of anhydrous THF to a reaction flask and stir for 30 minutes; dissolve 0.11 mol of 3-amino-1,2-epoxypropane in 300 ml of anhydrous THF and add 0.1 mol of N,N-diisopropylethylamine to prepare a mixed solution; slowly add the mixed solution dropwise to the reaction flask under an ice bath for 30 minutes and react at 40°C for 10 hours. After the reaction, distill under reduced pressure at 40°C for 2 hours, add 100 ml of 0.1M hydrochloric acid, stir thoroughly, and filter. Wash the filter cake with deionized water until neutral and dry it in a vacuum at 40°C for 8 hours to obtain intermediate 2; S3: Under nitrogen protection, add 0.21 mol of intermediate 2 and 350 ml of anhydrous THF to a reaction flask and stir for 30 minutes. Dissolve 0.1 mol of cystamine in 350 ml of anhydrous THF and add 0.21 mol of N,N-diisopropylethylamine to prepare a mixed solution. In an ice bath, slowly add the mixed solution dropwise to the reaction flask for 30 minutes and react at 75°C for 5 hours. After the reaction, distill under reduced pressure at 40°C for 2 hours, add 100 ml of 0.1M hydrochloric acid, stir thoroughly, and filter. Wash the filter cake with deionized water until neutral and dry it in a vacuum at 50°C for 8 hours to obtain intermediate 3. S4: Under nitrogen protection, 500 ml of anhydrous DMF, 0.1 mol of intermediate 3 and 0.1 mol of triethylamine were added to the reaction flask and stirred for 30 min. Then, 0.01 mol of BHT was added and 300 ml of a DMF solution containing 0.21 mol of dopamine was slowly added dropwise for 30 min. The reaction was carried out at 80 °C in the dark for 10 h. The reaction solution was cooled in an ice bath and the pH was adjusted to 4 with 0.5 M HCl. The product was purified by Sephadex LH-20 gel column chromatography (eluent: methanol / water). V / V =1:1), and freeze-dried at -50 °C for 48 h to obtain a modified toughening agent.

[0023] Example 4 Preparation of bulletproof composite material: Weigh by weight: 600 g of epoxy resin (E51 epoxy resin), 50 g of modified toughening agent (prepared in Example 1), 40 g of curing agent (hexamethylenediamine), 10 g of thermal stabilizer (2,6-di-tert-butyl-4-methylphenol), 10 g of inorganic filler (nanosilica), 5 g of coupling agent (KH-560 silane coupling agent), and 20 g of wetting agent (polyether-modified silicone oil).

[0024] S1: Add 600g epoxy resin and 2000ml N-methylpyrrolidone into the reactor, stir, heat to 60℃, stir for 10min, add 50g modified toughening agent, 10g heat stabilizer, 5g coupling agent, 20g wetting agent in sequence, stir for 20min, then add 10g inorganic filler, stir at 1500rpm for 30min, finally add 40g curing agent and stir for 20h to obtain a viscous resin glue.

[0025] S2: The Kevlar K129 aramid fiber was vacuum dried at 120°C for 2 hours, spread flat on the unwinding device of the impregnation machine, and the resin glue was added to the resin tank. The fiber tension was set to 4N / cm, the resin tank temperature was set to 60°C, and the impregnation speed was set to 1m / min. The resin glue content was controlled to 50wt% by a scraper. The impregnated fiber was then dried in a 50°C oven for 12 hours to obtain an aramid / resin prepreg.

[0026] S3: After cutting the prepreg by alternating layers of [0° / 90°] 8 (a total of 16 layers), the prepreg was placed in an autoclave and heated to 90°C at a rate of 2°C / min and maintained for 1 hour (pressure 5 MPa); the temperature was further raised to 120°C and maintained for 2 hours (pressure increased to 10 MPa); the temperature was then raised to 150°C and maintained for 1 hour (pressure 15 MPa), and the temperature was naturally lowered to below 60°C and the pressure was released to obtain a bullet-proof composite material.

[0027] Example 5 Preparation of bulletproof composite material: Weigh by weight: 650 g of epoxy resin (E51 epoxy resin), 65 g of modified toughening agent (prepared in Example 2), 45 g of curing agent (diethylenetriamine), 15 g of thermal stabilizer (2,6-di-tert-butyl-4-methylphenol), 15 g of inorganic filler (nano-montmorillonite), 8 g of coupling agent (KH-560 silane coupling agent), and 35 g of wetting agent (polyether-modified silicone oil).

[0028] S1: Add 650g epoxy resin and 2000ml N-methylpyrrolidone into the reactor, stir, heat to 60℃, stir for 10min, add 65g modified toughening agent, 15g heat stabilizer, 8g coupling agent, 35g wetting agent in sequence, stir for 20min, then add 15g inorganic filler, stir at 1800rpm for 30min, finally add 45g curing agent and stir for 20h to obtain a viscous resin glue.

[0029] S2: The Kevlar K129 aramid fiber was vacuum dried at 120°C for 2 hours, spread flat on the unwinding device of the impregnation machine, and the resin glue was added to the resin tank. The fiber tension was set to 5N / cm, the resin tank temperature was set to 60°C, and the impregnation speed was set to 1.5m / min. The resin glue content was controlled to 50wt% by a scraper. The impregnated fiber was then dried in a 50°C oven for 12 hours to obtain an aramid / resin prepreg.

[0030] S3: After cutting the prepreg by alternating layers of [0° / 90°] 8 (a total of 16 layers), the prepreg was placed in an autoclave and heated to 90°C at a rate of 2°C / min and maintained for 1 hour (pressure 5 MPa); the temperature was further raised to 120°C and maintained for 2 hours (pressure increased to 13 MPa); the temperature was then raised to 150°C and maintained for 1 hour (pressure 15 MPa), and the temperature was naturally lowered to below 60°C and the pressure was released to obtain a bullet-proof composite material.

[0031] Example 6 Preparation of bulletproof composite material: Weigh by weight: 700 g of epoxy resin (E51 epoxy resin), 80 g of modified toughening agent (prepared in Example 3), 50 g of curing agent (triethylenetetramine), 20 g of thermal stabilizer (2,6-di-tert-butyl-4-methylphenol), 20 g of inorganic filler (nanosilica), 10 g of coupling agent (KH-560 silane coupling agent), and 50 g of wetting agent (polyether-modified silicone oil).

[0032] S1: Add 700g epoxy resin and 2000ml N-methylpyrrolidone into the reactor, stir, heat to 60℃, stir for 10min, add 80g modified toughening agent, 20g heat stabilizer, 10g coupling agent, 50g wetting agent in sequence, stir for 20min, then add 20g inorganic filler, stir at 2000rpm for 30min, finally add 50g curing agent and stir for 20h to obtain a viscous resin glue.

[0033] S2: The Kevlar K129 aramid fiber was vacuum dried at 120°C for 2 hours, spread flat on the unwinding device of the impregnation machine, and the resin glue was added to the resin tank. The fiber tension was set to 6N / cm, the resin tank temperature was set to 60°C, and the impregnation speed was set to 2m / min. The resin glue content was controlled to 50wt% by a scraper. The impregnated fiber was then dried in a 50°C oven for 12 hours to obtain an aramid / resin prepreg.

[0034] S3: After cutting the prepreg by alternating layers of [0° / 90°] 8 (a total of 16 layers), the prepreg was placed in an autoclave and heated to 90°C at a rate of 2°C / min and maintained for 1 hour (pressure 5 MPa); the temperature was further raised to 120°C and maintained for 2 hours (pressure increased to 15 MPa); the temperature was then raised to 150°C and maintained for 1 hour (pressure 15 MPa), and the temperature was naturally lowered to below 60°C and the pressure was released to obtain a bullet-proof composite material.

[0035] Comparative Example 1 The raw material composition and process of the bullet-proof composite material are basically the same as those in Example 5, except that no modifying toughening agent is added to the resin matrix component.

[0036] Comparative Example 2 The raw material composition and process of the bullet-proof composite material are basically the same as those in Example 5, except that the modified toughening agent is replaced by an equal weight of a modified toughening agent prepared by the following method: The preparation method of the modified toughening agent is basically the same as that of Example 2, except that the cyanuric chloride in step S1 is replaced by an equal weight of 2,4,6-trichloropyrimidine.

[0037] Comparative Example 3 The raw material composition and process of the bullet-proof composite material are basically the same as those in Example 5, except that the modified toughening agent is replaced by an equal weight of a modified toughening agent prepared by the following method: The preparation method of the modified toughening agent is basically the same as that of Example 2, except that the 4-hydroxyphenylboric acid in step S1 is replaced by an equal weight of 4-hydroxybenzoic acid.

[0038] Comparative Example 4 The raw material composition and process of the bullet-proof composite material are basically the same as those in Example 5, except that the modified toughening agent is replaced by an equal weight of a modified toughening agent prepared by the following method: The preparation method of the modified toughening agent is substantially the same as that of Example 2, except that the cystamine in step S3 is replaced by an equal weight of 3,3'-thio-1-propylamine (CAS: 13643-20-4).

[0039] Comparative Example 5 The raw material composition and process of the bullet-proof composite material are basically the same as those in Example 5, except that the modified toughening agent is replaced by an equal weight of a modified toughening agent prepared by the following method: The preparation method of the modified toughening agent is basically the same as that of Example 2, except that the cystamine in step S3 is replaced by an equal weight of 2-(propyldithio)-ethylamine (CAS: 81134-72-7).

[0040] The nano-silica used in the examples and comparative examples of the present application is rutile silica with a particle size uniformly distributed between 5 and 50 nm, purchased from Shanghai Yuanye Biotechnology Co., Ltd.; the nano-montmorillonite is nano-montmorillonite with a mesh size of 2000 mesh, purchased from Shanghai Wanzhao Fine Chemical Co., Ltd.; the brand of the polyether-modified silicone oil is Dow Corning DC193.

[0041] The ballistic performance and self-repair performance of the ballistic-resistant composite materials prepared in Examples 4-6 and Comparative Examples 1-5 were tested. The test results are shown in Table 1.

[0042] The ballistic performance of bulletproof composite materials is determined by the ballistic limit velocity ( V 50 ) and energy absorption as evaluation indicators, ballistic impact tests were conducted according to the Chinese military body armor standard GJB4300A-2012. The ballistic impact test apparatus consisted of a fragmentation simulation projectile (FSP), a 7.62 mm caliber fragmentation simulation projectile launcher, a velocity measurement device, a composite laminate, and a backing support. The composite laminate measured 300 mm x 300 mm. The FSP was made of 45-grade steel with a surface hardness of HRC30, a diameter of 5.5 mm, and a mass of 1.1 g. The distance between the launcher and the laminate was 5 meters, and each specimen was shot at least six times. V 50 The energy absorption is characterized by specific energy absorption (SEA), which is calculated by the following formula: SEA = (1 / 2m V 50 2 ) / Areal density, where m is the mass of FSP (kg), Areal density is the surface density of the composite material (kg / m 2 ). Areal density is tested according to HB 7736.2-2004 standard.

[0043] The self-repairing properties of bulletproof composite materials before and after repair V 50 The self-repair efficiency H = after repair V 50 / Before Repair V50 ×100%.

[0044] Table 1 Performance indicators of bulletproof composite materials

[0045] It can be seen from the data in Table 1 that the bulletproof composite material prepared in the present application has excellent ballistic protection performance, resistance to multiple impacts and self-repairing performance.

[0046] Comparative Example 1 shows a ballistic composite material prepared without a modified toughening agent. Its ballistic limit velocity, energy absorption, and self-healing properties are all poor. This demonstrates that the synergistic effect of the rigid ring core and multifunctional groups (phenylboronic acid, disulfide bonds, and dopamine) introduced into the modified toughening agent significantly improves the composite's multiple properties. The dopamine grafted to the end of the modified toughening agent forms hydrogen bonds and π-π stacking with the amide groups on the aramid fiber surface, strengthening the interfacial bonding between the fiber and the resin, effectively inhibiting impact crack propagation along the interface, and improving the composite's resistance to multiple impacts.

[0047] The ballistic-resistant composite material prepared using 2,4,6-trichloropyrimidine in Comparative Example 2 exhibits poor ballistic performance, primarily due to the asymmetric distribution of nitrogen atoms in the pyrimidine ring and the complex molecular conformation of the reaction product, which can create localized stress concentration points and easily induce crack propagation under ballistic impact. However, when the composite is impacted, the triazine ring (rigid core) of the cyanuric acid chloride undergoes bond angle deformation, absorbing additional energy and improving the composite's ballistic limit. Furthermore, the rigid structure of the triazine ring core in the modified toughening agent maintains the composite's structural integrity under impact, enhancing the composite's fracture toughness and, consequently, its ballistic-resistant performance.

[0048] The self-healing properties of the ballistic-resistant composites prepared in Comparative Examples 3 and 4 were inferior to those of Example 5, primarily due to the lack of dynamic boronic acid groups and disulfide bonds. In humid environments, broken BO bonds can recombine through hydrolysis-esterification reactions; under thermal stimulation, disulfide bonds can be reconstituted through thiol-disulfide exchange, significantly improving the self-healing properties of the ballistic-resistant composites.

[0049] The ballistic performance of the ballistic-resistant composite material prepared in Comparative Example 5 is inferior to that of Example 5. This is because 2-(propyldithio)-ethylamine contains only one amino group, and the prepared modified plasticizer contains only one dopamine group and one phenylboronic acid group, resulting in a decrease in its interfacial strength and energy absorption, thereby affecting the multiple impact resistance and ballistic protection performance of the ballistic-resistant composite material.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. However, any equivalent changes, modifications and evolutions made by ordinary technicians in this field without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A bulletproof composite material, characterized in that: It is composed of aramid fiber and resin matrix; The resin matrix includes the following raw materials in parts by weight: Epoxy resin: 60-70 parts; Modified toughening agent: 5-8 parts; Curing agent: 4-5 parts; Heat stabilizer: 1-2 parts; Inorganic filler: 1-2 parts; Coupling agent: 0.5-1 part; Wetting agent: 2-5 parts; The chemical structural formula of the modified toughening agent is as follows: 。 2. The bulletproof composite material according to claim 1, characterized in that: The modified toughening agent is prepared by the following method: S1: Under nitrogen protection, cyanuric chloride, 4-hydroxyphenylboronic acid and anhydrous acetonitrile were mixed, triethylamine was added dropwise, and the reaction was carried out for 4-5 hours. After post-treatment, intermediate 1 was obtained; S2: Under nitrogen protection, mix the intermediate 1, 3-amino-1,2-epoxypropane and anhydrous THF, add N,N-diisopropylethylamine, react for 10-12 hours, and post-treat to obtain the intermediate 2; S3: Under nitrogen protection, intermediate 2, cystamine and anhydrous THF were mixed, N, N-diisopropylethylamine was added, and the reaction was carried out for 5-6 hours. After post-treatment, intermediate 3 was obtained; S4: Under nitrogen protection, the intermediate 3, dopamine and anhydrous DMF were mixed, reacted for 10-12 hours, and post-treated to obtain a modified toughening agent.

3. The bulletproof composite material according to claim 2, characterized in that: In step S1, the molar ratio of cyanuric chloride to 4-hydroxyphenylboric acid is 1:(1-1.2).

4. The bulletproof composite material according to claim 2, characterized in that: In step S2, the molar ratio of the intermediate 1 and 3-amino-1,2-epoxypropane is 1:(1.05-1.1).

5. The bulletproof composite material according to claim 2, characterized in that: In step S3, the molar ratio of the intermediate 2 to cystamine is (2.05-2.1):

1.

6. The bulletproof composite material according to claim 2, characterized in that: In step S4, the molar ratio of the intermediate 3 to dopamine is 1:(2-2.1).

7. The bulletproof composite material according to claim 1, characterized in that: The heat stabilizer is 2,6-di-tert-butyl-4-methylphenol; the coupling agent is KH-560 silane coupling agent; and the wetting agent is polyether-modified silicone oil.

8. The bulletproof composite material according to claim 1, characterized in that: The curing agent is one of hexamethylenediamine, diethylenetriamine and triethylenetetramine; and the inorganic filler is one of nano-silicon dioxide and nano-montmorillonite.

9. The bulletproof composite material according to claim 1, characterized in that: The aramid fiber is Kevlar K129 fiber, and the epoxy resin is E51 epoxy resin.

10. A method for preparing the bulletproof composite material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Add 60-70 parts by weight of epoxy resin and 200 parts by weight of N-methylpyrrolidone into a reactor, heat to 60°C, stir, add 5-8 parts by weight of a modified toughening agent, 1-2 parts by weight of a heat stabilizer, 0.5-1 parts by weight of a coupling agent, and 2-5 parts by weight of a wetting agent in sequence, stir for 20 minutes, then add 1-2 parts by weight of an inorganic filler, stir at 1500 rpm for 30 minutes, and finally add 4-5 parts by weight of a curing agent and stir for 20 hours to obtain a resin glue; S2: The aramid fiber was vacuum dried at 120°C for 2 hours, and then laid flat on the unwinding device of the impregnation machine. The resin glue was added to the resin tank. The fiber tension was set to 4-6 N / cm, the resin tank temperature was set to 60°C, and the impregnation speed was set to 1-2 m / min. The resin glue content was controlled to 50 wt% by a scraper. The impregnated fiber was then dried in a 50°C oven for 12 hours to obtain an aramid fiber / resin prepreg. S3: After the prepreg is laid alternately at [0° / 90°] 8, it is cut and placed in an autoclave for hot pressing to obtain a bulletproof composite material.

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