Preparation method of graphene composite bulletproof material

Abstract

The invention discloses a preparation method of a graphene composite bulletproof material, and belongs to the technical field of bulletproof material preparation, polyacrylonitrile is used as a carbon fiber precursor, zinc oxide coated PMMA microspheres are used as a pyrolysis template, and carbon fibers with a porous structure are prepared through high-temperature carbonization; porous carbon fibers are subjected to surface modification by adopting polydopamine and graphene oxide, and then gamma-methacryloxypropyltrimethoxysilane is used for treatment, so that the interface bonding strength of the graphene oxide and a matrix is remarkably improved, and the problem of insufficient energy dissipation caused by interface failure in the ballistic impact process is effectively avoided; therefore, the buffering capability of the composite material on high-speed impact load is obviously improved; the zinc oxide nanospheres have excellent thermal conductivity, so that the thermal conduction efficiency in the pre-oxidation process can be remarkably improved, and the problems of long reaction time, low efficiency and high production cost in the traditional pre-oxidation process are avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of bulletproof material preparation, and specifically relates to a method for preparing a graphene composite bulletproof material. Background Art

[0002] In the prior art, bulletproof layers are primarily constructed from single or composite materials, such as metal, ceramic sheets, fiberglass, nylon (PA), Kevlar, ultra-high molecular weight polyethylene fibers, and liquid protective materials. These layers protect the human body by deflecting and / or trapping bullets and shrapnel, dissipating the kinetic energy of the impact. However, with the increasing lethality, accuracy, and range of firearms, and the increasing severity of casualties from terrorist and counter-terrorism activities, gun-related crimes, and crime prevention operations, the problem of bulletproofing individual soldiers and their accompanying equipment has become increasingly prominent. Existing bulletproof materials often suffer from heavy weight, poor flexibility and air permeability, and inability to meet the requirements for protection against injuries from modern firearms. Researchers have primarily focused on improving the structural design and placement of bulletproof layers, without fundamentally improving the composition or performance of the materials.

[0003] Chinese patent publication number CN105670270B discloses a method for preparing a graphene composite bulletproof material. Graphene is compounded with a polymer resin material by a physical mixing method to produce a composite bulletproof material with good mechanical strength and temperature resistance. However, the graphene is only combined with the polymer resin material by physical blending, and the interfacial bonding strength between the two is low, which weakens the graphene's ability to buffer the impact force of the material. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a graphene composite bulletproof material. Polyacrylonitrile is used as a carbon fiber precursor, zinc oxide-coated polymethyl methacrylate (PMMA) microspheres are used as a pyrolysis template, and carbon fibers with a porous structure are prepared by high-temperature carbonization. To improve the interface performance of the composite material, polydopamine is used as a bridge and then treated with γ-methacryloxypropyltrimethoxysilane. This significantly increases the interfacial bonding strength between graphene oxide and phenolic resin, effectively avoiding the problem of insufficient energy dissipation caused by interface failure during ballistic impact, thereby significantly improving the composite material's buffering capacity against high-speed impact loads.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a graphene composite bullet-proof material comprises the following steps:

[0007] Step 1: The zinc oxide nanospheres are treated with 3-aminopropyltriethoxysilane to obtain modified zinc oxide nanospheres with amino groups on the surface. The PMMA microspheres are hydrolyzed under alkaline conditions to release carboxyl groups, and the modified zinc oxide nanospheres are grafted onto them through an amidation reaction to obtain zinc oxide-coated PMMA microspheres.

[0008] Step 2: The spinning solution containing polyacrylonitrile and zinc oxide-coated PMMA microspheres is wet-processed to prepare polymer fiber precursors, which are then pre-oxidized and carbonized to obtain porous carbon fiber powder.

[0009] Step 3: The porous carbon fiber powder is coated with polydopamine, and the amino group of the polydopamine undergoes an amidation reaction with the carboxyl group of the graphite oxide to obtain graphene oxide-coated carbon fiber.

[0010] Step 4: The graphene oxide coated carbon fiber is treated with γ-methacryloxypropyltrimethoxysilane, and then the functionalized graphene oxide coated carbon fiber is mixed with phenolic resin and cured to obtain a graphene composite bulletproof material.

[0011] Furthermore, the specific preparation steps of modified zinc oxide nanospheres are as follows:

[0012] Zinc nitrate hexahydrate and deionized water are added to a reactor, stirred at 80-90°C and 500-600 r / min for 40-50 minutes, then ammonia water is added, stirring is continued until a white precipitate is generated, filtered, and the precipitate is washed 2-3 times with deionized water and anhydrous ethanol to obtain zinc oxide nanospheres; zinc oxide nanospheres, anhydrous ethanol and deionized water are added to a reactor, stirred at 60-70°C and 500-600 r / min for 10-15 minutes, then 3-aminopropyltriethoxysilane is added, the pH value is adjusted to 3-4 with hydrochloric acid solution, and the stirring reaction is continued for 6-7 hours to obtain modified zinc oxide nanospheres with a particle size of 40-50 nm.

[0013] Furthermore, the usage ratio of zinc nitrate hexahydrate, deionized water and ammonia water is 70-80 g: 1-2 L: 80-90 mL.

[0014] Furthermore, the usage ratio of zinc oxide nanospheres, anhydrous ethanol, deionized water and 3-aminopropyltriethoxysilane is 50-60 g: 1-2 L: 3-4 L: 100-120 mL.

[0015] Furthermore, the specific preparation steps of zinc oxide-coated PMMA microspheres are as follows:

[0016] PMMA microspheres with a particle size of 12-15 μm and deionized water were added to a reactor, stirred at 20-25°C and 500-600 r / min for 2-3 minutes, then 0.05 g / mL NaOH solution was added, heated to 80-90°C, and stirred for 12-14 hours. Then, modified zinc oxide nanospheres and N,N'-dicyclohexylcarbodiimide were added, and stirring was continued for 6-7 hours. The mixture was filtered, and the precipitate was washed with deionized water and anhydrous ethanol 2-3 times to obtain zinc oxide-coated PMMA microspheres.

[0017] Furthermore, the usage ratio of PMMA microspheres, deionized water, NaOH solution, modified zinc oxide nanospheres and N,N'-dicyclohexylcarbodiimide is 15-20 g: 270-300 mL: 30-40 mL: 12-14 g: 10-12 g.

[0018] Furthermore, the specific steps for preparing the polymer fiber precursor are as follows:

[0019] Polyacrylonitrile and N,N-dimethylformamide are added to a reactor in a ratio of 20-25 g:80-90 mL, and stirred at 60-70° C. and 500-600 r / min for 40-50 min to obtain a polyacrylonitrile dispersion. Zinc oxide-coated PMMA microspheres and N,N-dimethylformamide are then added to a reactor in a ratio of 5-6 g:20-30 mL, and stirred at 60-70° C. and 500-600 r / min for 40-50 min to obtain a zinc oxide-coated PMMA microsphere dispersion. The polyacrylonitrile dispersion and the zinc oxide-coated PMMA microsphere dispersion are stirred and mixed in a volume ratio of 3:1 to obtain a polymer blend solution, which is placed in a vacuum oven at 50-60° C. for degassing for 30-40 min to obtain a spinning solution, and polymer fiber precursors are obtained by wet spinning.

[0020] Furthermore, the specific steps for preparing the porous carbon fiber powder are as follows:

[0021] The polymer fiber precursor is placed in a muffle furnace for pre-oxidation treatment, heated to 280-300°C at a heating rate of 5-6°C / min and kept warm for 20-30 minutes to obtain a pre-oxidized fiber precursor; the pre-oxidized fiber precursor is placed in a high-temperature carbonization furnace, and under nitrogen protection, heated to 380-400°C at a heating rate of 5-6°C / min, kept warm for 1-2 hours, heated to 450-500°C at a heating rate of 5-6°C / min, kept warm for 1-2 hours, heated to 900-1000°C at a heating rate of 1-2 hours, naturally cooled to room temperature, crushed, and sieved to obtain a porous carbon fiber powder with a diameter of 70-90 μm.

[0022] Furthermore, the specific preparation steps of polydopamine coating are as follows:

[0023] Tris-HCl buffer with a pH value of 8.5, dopamine and porous carbon fiber powder are added to a reactor, stirred at 30-40°C and 500-600 r / min for 15-16 hours, filtered, the porous carbon fiber is taken out, washed with deionized water 2-3 times, and vacuum dried at 60-80°C for 1-2 hours to obtain polydopamine-coated carbon fiber.

[0024] Furthermore, the usage ratio of Tris-HCl buffer, dopamine and porous carbon fiber powder is 3-4L: 4-5g: 15-20g.

[0025] Furthermore, the specific preparation steps of graphene oxide coated carbon fiber are as follows:

[0026] Graphene oxide, anhydrous ethanol and deionized water were added to a reactor, stirred at 70-80°C and 500-600 r / min for 10-15 minutes, and then polydopamine-coated carbon fiber and N,N'-dicyclohexylcarbodiimide were added. The mixture was stirred for 8-9 hours and filtered. The precipitate was washed with deionized water and anhydrous ethanol for 2-3 times, and vacuum dried at 60-80°C for 1-2 hours to obtain graphene oxide-coated carbon fiber.

[0027] Furthermore, the usage ratio of graphene oxide, anhydrous ethanol, deionized water, polydopamine-coated carbon fiber and N,N'-dicyclohexylcarbodiimide is 15-20 g: 1-2 L: 3-4 L: 15-20 g.

[0028] Furthermore, the specific preparation steps of functionalized graphene oxide coated carbon fiber are as follows:

[0029] Graphene oxide-coated carbon fiber, anhydrous ethanol and deionized water are added to a reactor, stirred at 60-70°C and 500-600r / min for 10-15min, then γ-methacryloxypropyltrimethoxysilane is added, the pH value is adjusted to 3-4 with hydrochloric acid solution, and the stirring reaction is continued for 6-7h. The mixture is filtered, and the precipitate is washed 2-3 times with deionized water and anhydrous ethanol, and vacuum dried at 60-80°C for 1-2h to obtain functionalized graphene oxide-coated carbon fiber.

[0030] Furthermore, the usage ratio of graphene oxide-coated carbon fiber, anhydrous ethanol, deionized water and γ-methacryloxypropyltrimethoxysilane is 20-30 g: 1-2 L: 3-4 L: 100-120 mL.

[0031] Furthermore, the specific preparation steps of the graphene composite bulletproof material are as follows:

[0032] Functionalized graphene oxide-coated carbon fiber, polyethylene glycol and liquid phenolic resin are mixed uniformly in a dosage ratio of 15-20 g: 0.1-0.2 g: 80-90 g under the conditions of ultrasonic power of 400-500 W and shear speed of 2000-3000 r / min, dried to form a film, and cured to obtain a graphene composite bulletproof material.

[0033] Beneficial effects of the present invention:

[0034] 1. The graphene composite bullet-proof material prepared by the present invention uses polyacrylonitrile as a carbon fiber precursor, zinc oxide-coated PMMA microspheres as a pyrolytic polymer, and then is coated with polydopamine to serve as a bridge. The graphene oxide is then treated with γ-methacryloxypropyltrimethoxysilane to significantly increase the interfacial bonding strength between the graphene oxide and the phenolic resin, resulting in excellent strength, little depression after being hit by a bullet, and the ability to effectively buffer the impact force caused by the bullet. The problem of insufficient energy dissipation due to interface failure during ballistic impact can be effectively avoided, thereby significantly improving the composite material's buffering capacity against high-speed impact loads.

[0035] 2. The porous carbon fiber of the present invention is prepared by treating zinc oxide nanospheres with 3-aminopropyltriethoxysilane to obtain modified zinc oxide nanospheres with amino groups on the surface, which undergo amidation reaction with carboxyl groups generated by hydrolysis of PMMA microspheres under alkaline conditions to obtain zinc oxide-coated PMMA microspheres. During the spinning and stretching process, the zinc oxide-coated PMMA microspheres serve as a dispersed phase and form small spheres under the action of spinning tension to cover the polyacrylonitrile fiber precursor. The pyrolysis polymer is used, and polyacrylonitrile is used as a carbon fiber precursor. During the pre-oxidation of polyacrylonitrile, the polyacrylonitrile molecular chain undergoes a cyclization reaction in an air atmosphere, and the zinc oxide-coated PMMA microspheres are formed. MMA microspheres pyrolyze to generate gas, thereby forming porous carbon fibers with uniform pores on the carbon fibers. The surface-coated zinc oxide nanospheres have a high thermal decomposition temperature and continue to exist on the surface of the carbon fibers. The high thermal conductivity of the zinc oxide nanospheres can improve the efficiency of pre-oxidation and avoid the problems of long reaction time, low efficiency and high production cost in the traditional pre-oxidation process. In addition, the existing zinc oxide nanospheres can serve as a reinforcing phase to improve the bulletproof strength of the porous carbon fibers. The presence of zinc oxide increases the surface roughness of the porous carbon fibers, which is beneficial to the coating of polydopamine and provides sufficient active sites for the subsequent coating of graphene oxide.

[0036] 3. After the graphene oxide-coated carbon fiber is treated with γ-methacryloyloxypropyltrimethoxysilane, a functionalized graphene oxide-coated carbon fiber with methacryloyloxy groups containing double bonds on the surface is obtained, which significantly increases the interfacial bonding strength between the graphene oxide and the phenolic resin, giving it excellent strength. The degree of concavity after being hit by a bullet is small, and it can effectively cushion the impact force caused by the bullet. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Example 1: A method for preparing a graphene composite bullet-proof material, comprising the following steps:

[0039] S1: 70g of zinc nitrate hexahydrate and 1L of deionized water were added to a reactor, stirred at 80°C and 500r / min for 40min, then 80mL of ammonia water was added and stirring was continued until a white precipitate was produced. The mixture was filtered and washed twice with deionized water and anhydrous ethanol to obtain zinc oxide nanospheres. 50g of zinc oxide nanospheres, 1L of anhydrous ethanol and 3L of deionized water were added to a reactor, stirred at 60°C and 500r / min for 10min, then 100mL of 3-aminopropyltriethoxysilane was added, the pH value was adjusted to 3 with hydrochloric acid solution, and the reaction was stirred for 6h to obtain modified zinc oxide nanospheres with a particle size of 40nm.

[0040] The modified zinc oxide nanospheres with amino groups on the surface are obtained by reacting the hydroxyl groups on the surface of the zinc oxide nanospheres with the silanol groups generated by the hydrolysis of 3-aminopropyltriethoxysilane.

[0041] S2: 15 g of PMMA microspheres with a particle size of 12-15 μm and 270 mL of deionized water were added to the reactor, stirred at 20°C and 500 r / min for 2 min, then 30 mL of 0.05 g / mL NaOH solution was added, heated to 80°C, and stirred for 12 h. Then, modified zinc oxide nanospheres and 10 g of N,N'-dicyclohexylcarbodiimide were added, and stirring was continued for 6 h. The mixture was filtered and the precipitate was washed twice with deionized water and anhydrous ethanol to obtain zinc oxide-coated PMMA microspheres.

[0042] The side chain ester groups of PMMA microspheres are hydrolyzed under alkaline conditions to generate carboxyl groups. Under the action of a catalyst, the carboxyl groups undergo amidation reaction with the amino groups on the surface of the modified zinc oxide nanospheres to obtain zinc oxide-coated PMMA microspheres.

[0043] S3: Add 20 g of polyacrylonitrile and 80 mL of N,N-dimethylformamide into a reactor, stir at 60°C and 500 r / min for 40 min to obtain a polyacrylonitrile dispersion; then add 5 g of zinc oxide-coated PMMA microspheres and 20 mL of N,N-dimethylformamide into a reactor, stir at 60°C and 500 r / min for 40 min to obtain a zinc oxide-coated PMMA microsphere dispersion; stir and mix the polyacrylonitrile dispersion and the zinc oxide-coated PMMA microsphere dispersion in a volume ratio of 3:1 to obtain a polymer blend solution, place it in a vacuum oven at 50°C for degassing for 30 min to obtain a spinning solution, and obtain polymer fiber precursor by wet spinning.

[0044] Zinc oxide-coated PMMA microspheres are used as pyrolysis polymers. During the pre-oxidation of polyacrylonitrile, the zinc oxide-coated PMMA microspheres serve as the dispersed phase during the spinning and stretching process, and form small balls covering the polyacrylonitrile fiber precursor under the action of spinning tension.

[0045] S4: The polymer fiber precursor is placed in a muffle furnace for pre-oxidation treatment, and is heated to 280°C at a heating rate of 5°C / min and kept warm for 20 minutes to obtain a pre-oxidized fiber precursor; the pre-oxidized fiber precursor is placed in a high-temperature carbonization furnace, and under nitrogen protection, is heated to 380°C at a heating rate of 5°C / min, and kept warm for 1 hour, heated to 450°C and kept warm for 1 hour, heated to 900°C and kept warm for 1 hour, and naturally cooled to room temperature, crushed, and sieved to obtain a porous carbon fiber powder with a diameter of 70-90 μm.

[0046] S5: Add 3L of Tris-HCl buffer with a pH value of 8.5, 4g of dopamine, and 15g of porous carbon fiber powder into a reactor, stir at 30°C and 500r / min for 15h, filter, take out the porous carbon fiber, wash it twice with deionized water, and vacuum dry it at 60°C for 1h to obtain polydopamine-coated carbon fiber.

[0047] The porous carbon fibers are dispersed in a dopamine solution, adsorbed on the surface of the porous carbon fibers by electrostatic adsorption, and then polymerized on the surface to form a polydopamine coating.

[0048] S6: Add 15 g of graphene oxide, 1 L of anhydrous ethanol and 3 L of deionized water into the reactor, stir at 70 ° C and 500 r / min for 10 min, then add 15 g of polydopamine-coated carbon fiber and 10 g of N, N'-dicyclohexylcarbodiimide, continue stirring for 8 h, filter, wash the precipitate with deionized water and anhydrous ethanol twice, and dry it in vacuum at 60 ° C for 1 h to obtain graphene oxide-coated carbon fiber.

[0049] Under the action of the catalyst, the amino group of polydopamine acts as a bridge to undergo an amidation reaction with the edge carboxyl group of graphite oxide, so that graphene oxide is evenly coated on the surface of the porous carbon fiber.

[0050] S7: Add 20 g of graphene oxide-coated carbon fiber, 1 L of anhydrous ethanol and 3 L of deionized water into the reactor, stir at 60 ° C and 500 r / min for 10 min, then add 100 mL of γ-methacryloxypropyltrimethoxysilane, adjust the pH value to 3 with hydrochloric acid solution, continue stirring and react for 6 h, filter, wash the precipitate with deionized water and anhydrous ethanol twice, and dry it in vacuum at 60 ° C for 1 h to obtain functionalized graphene oxide-coated carbon fiber.

[0051] The hydroxyl groups on the surface of the graphene oxide-coated carbon fiber combine with the silanol groups generated by the hydrolysis of γ-methacryloyloxypropyltrimethoxysilane to obtain methacryloyloxy groups containing double bonds on the surface.

[0052] S8: 15 g of functionalized graphene oxide-coated carbon fiber, 0.1 g of polyethylene glycol, and 80 g of liquid phenolic resin were mixed uniformly under the conditions of ultrasonic power of 400 W and shear rate of 2000 r / min, dried to form a film, and cured to obtain a graphene composite bulletproof material.

[0053] Example 2: A method for preparing a graphene composite bullet-proof material, comprising the following steps:

[0054] S1: 75 g of zinc nitrate hexahydrate and 1.5 L of deionized water were added to a reactor, stirred at 85 ° C and 550 r / min for 45 min, then 85 mL of ammonia water was added and stirring was continued until a white precipitate was produced. The mixture was filtered and washed twice with deionized water and anhydrous ethanol to obtain zinc oxide nanospheres; 55 g of zinc oxide nanospheres, 1.5 L of anhydrous ethanol and 3.5 L of deionized water were added to a reactor, stirred at 65 ° C and 550 r / min for 12.5 min, then 110 mL of 3-aminopropyltriethoxysilane was added, the pH value was adjusted to 3.5 with hydrochloric acid solution, and the reaction was stirred for 6.5 h to obtain modified zinc oxide nanospheres with a particle size of 45 nm.

[0055] S2: 17.5 g of PMMA microspheres with a particle size of 12-15 μm and 285 mL of deionized water were added to the reactor, stirred at 22.5 ° C and 550 r / min for 2.5 min, then 35 mL of 0.05 g / mL NaOH solution was added, heated to 85 ° C, and continued to stir for 13 h. Then, modified zinc oxide nanospheres and 11 g of N, N'-dicyclohexylcarbodiimide were added, and stirring was continued for 6.5 h. Filtered, the precipitate was washed twice with deionized water and anhydrous ethanol to obtain zinc oxide-coated PMMA microspheres.

[0056] S3: Add 22.5 g of polyacrylonitrile and 85 mL of N,N-dimethylformamide into a reactor, stir at 65°C and 550 r / min for 45 min to obtain a polyacrylonitrile dispersion; then add 5.5 g of zinc oxide-coated PMMA microspheres and 25 mL of N,N-dimethylformamide into a reactor, stir at 65°C and 550 r / min for 45 min to obtain a zinc oxide-coated PMMA microsphere dispersion; stir and mix the polyacrylonitrile dispersion and the zinc oxide-coated PMMA microsphere dispersion in a volume ratio of 3:1 to obtain a polymer blend solution, place it in a vacuum oven at 55°C for degassing for 35 min to obtain a spinning solution, and obtain polymer fiber precursor by wet spinning.

[0057] S4: The polymer fiber precursor is placed in a muffle furnace for pre-oxidation treatment, and is heated to 290°C at a heating rate of 5.5°C / min and kept warm for 25 minutes to obtain a pre-oxidized fiber precursor; the pre-oxidized fiber precursor is placed in a high-temperature carbonization furnace, and under nitrogen protection, is heated to 390°C at a heating rate of 5.5°C / min, and kept warm for 1.5 hours, heated to 475°C and kept warm for 1.5 hours, heated to 950°C and kept warm for 1.5 hours, and naturally cooled to room temperature, crushed, and sieved to obtain a porous carbon fiber powder with a diameter of 70-90 μm.

[0058] S5: Add 3.5 L of Tris-HCl buffer with a pH value of 8.5, 4.5 g of dopamine, and 18 g of porous carbon fiber powder into a reactor, stir at 35°C and 550 r / min for 17 h, filter, take out the porous carbon fiber, wash it twice with deionized water, and vacuum dry it at 70°C for 1.2 h to obtain polydopamine-coated carbon fiber.

[0059] S6: Add 17.5 g of graphene oxide, 1.5 L of anhydrous ethanol and 3.5 L of deionized water into the reactor, stir at 775 ° C and 550 r / min for 12.5 min, then add 17.5 g of polydopamine-coated carbon fiber and 11 g of N, N'-dicyclohexylcarbodiimide, continue stirring for 8.5 h, filter, wash the precipitate with deionized water and anhydrous ethanol twice, and vacuum dry at 70 ° C for 1.5 h to obtain graphene oxide-coated carbon fiber.

[0060] S7: 25 g of graphene oxide-coated carbon fiber, 1.5 L of anhydrous ethanol and 3.5 L of deionized water were added to the reactor, stirred at 65 ° C and 550 r / min for 12.5 min, then 110 mL of γ-methacryloxypropyltrimethoxysilane was added, the pH value was adjusted to 3.5 with hydrochloric acid solution, and the stirring reaction was continued for 6.5 h. After filtering, the precipitate was washed twice with deionized water and anhydrous ethanol, and vacuum dried at 70 ° C for 1.5 h to obtain functionalized graphene oxide-coated carbon fiber.

[0061] S8: 17.5 g of functionalized graphene oxide-coated carbon fiber, 0.15 g of polyethylene glycol, and 85 g of liquid phenolic resin were mixed uniformly under the conditions of ultrasonic power of 450 W and shear rate of 2500 r / min, dried to form a film, and cured to obtain a graphene composite bulletproof material.

[0062] Example 3: A method for preparing a graphene composite bullet-proof material, comprising the following steps:

[0063] S1: 80g of zinc nitrate hexahydrate and 2L of deionized water were added to a reactor, stirred at 90°C and 600r / min for 50min, then 90mL of ammonia water was added and stirring was continued until a white precipitate was produced. The mixture was filtered and washed three times with deionized water and anhydrous ethanol to obtain zinc oxide nanospheres. 60g of zinc oxide nanospheres, 2L of anhydrous ethanol and 4L of deionized water were added to a reactor, stirred at 70°C and 600r / min for 15min, then 120mL of 3-aminopropyltriethoxysilane was added, the pH value was adjusted to 4 with hydrochloric acid solution, and the reaction was stirred for 7h to obtain modified zinc oxide nanospheres with a particle size of 50nm.

[0064] S2: 20 g of PMMA microspheres with a particle size of 12-15 μm and 300 mL of deionized water were added to the reactor, stirred at 25°C and 600 r / min for 3 min, then 40 mL of 0.05 g / mL NaOH solution was added, heated to 90°C, and stirred for 14 h. Then, modified zinc oxide nanospheres and 12 g of N,N'-dicyclohexylcarbodiimide were added, and stirring was continued for 7 h. The mixture was filtered and the precipitate was washed three times with deionized water and anhydrous ethanol to obtain zinc oxide-coated PMMA microspheres.

[0065] S3: Add 25 g of polyacrylonitrile and 90 mL of N,N-dimethylformamide into a reactor, stir at 70°C and 600 r / min for 50 min to obtain a polyacrylonitrile dispersion; then add 6 g of zinc oxide-coated PMMA microspheres and 30 mL of N,N-dimethylformamide into a reactor, stir at 70°C and 600 r / min for 50 min to obtain a zinc oxide-coated PMMA microsphere dispersion; stir and mix the polyacrylonitrile dispersion and the zinc oxide-coated PMMA microsphere dispersion in a volume ratio of 3:1 to obtain a polymer blend solution, place it in a vacuum oven at 60°C for degassing for 40 min to obtain a spinning solution, and obtain polymer fiber precursor by wet spinning.

[0066] S4: The polymer fiber precursor is placed in a muffle furnace for pre-oxidation treatment, and is heated to 300°C at a heating rate of 6°C / min and kept warm for 30 minutes to obtain a pre-oxidized fiber precursor; the pre-oxidized fiber precursor is placed in a high-temperature carbonization furnace, and under nitrogen protection, is heated to 400°C at a heating rate of 6°C / min, and kept warm for 2 hours, heated to 500°C and kept warm for 2 hours, and heated to 1000°C and kept warm for 2 hours, and naturally cooled to room temperature, crushed, and sieved to obtain a porous carbon fiber powder with a diameter of 70-90 μm.

[0067] S5: Add 4 L of Tris-HCl buffer (pH 8.5), 5 g of dopamine, and 20 g of porous carbon fiber powder into a reactor, stir at 40°C and 600 rpm for 16 h, filter, take out the porous carbon fiber, wash it three times with deionized water, and vacuum dry it at 80°C for 2 h to obtain polydopamine-coated carbon fiber.

[0068] S6: Add 20 g of graphene oxide, 2 L of anhydrous ethanol and 4 L of deionized water into the reactor, stir at 80 ° C and 600 r / min for 15 min, then add 20 g of polydopamine-coated carbon fiber, continue stirring for 9 h, and add 12 g of N, N'-dicyclohexylcarbodiimide, filter, wash the precipitate with deionized water and anhydrous ethanol three times, and vacuum dry at 80 ° C for 2 h to obtain graphene oxide-coated carbon fiber.

[0069] S7: 30 g of graphene oxide-coated carbon fiber, 2 L of anhydrous ethanol and 4 L of deionized water were added to the reactor, stirred at 70 ° C and 600 r / min for 15 min, then 120 mL of γ-methacryloxypropyltrimethoxysilane was added, the pH value was adjusted to 4 with hydrochloric acid solution, and the stirring reaction was continued for 7 h. After filtering, the precipitate was washed with deionized water and anhydrous ethanol for 3 times, and vacuum dried at 80 ° C for 2 h to obtain functionalized graphene oxide-coated carbon fiber.

[0070] S8: 20 g of functionalized graphene oxide-coated carbon fiber, 0.2 g of polyethylene glycol, and 90 g of liquid phenolic resin were mixed uniformly under the conditions of ultrasonic power of 500 W and shear rate of 3000 r / min, dried to form a film, and cured to obtain a graphene composite bulletproof material.

[0071] Comparative Example 1: Based on Example 3, the zinc oxide-coated PMMA microspheres in step S2 were replaced with PMMA microspheres as the pyrolysis polymer, and the remaining steps remained unchanged to obtain a graphene composite bulletproof material.

[0072] Comparative Example 2: Based on Example 3, the porous carbon fiber powder in step S4 is replaced with conventional commercially available carbon fiber powder with a particle size of 50-60 μm, and the remaining steps remain unchanged to obtain a graphene composite bulletproof material.

[0073] Comparative Example 3: Based on Example 3, without step S5, the polydopamine-coated carbon fiber in step S6 is replaced by the porous carbon fiber in step S4, and the other steps remain unchanged to obtain a graphene composite bulletproof material.

[0074] Examples and Comparative Examples:

[0075] Liquid phenolic resin is a thermosetting resin with a curing temperature of 170-190°C and was purchased from Henan Zhongfan Dongsheng New Materials Technology Co., Ltd.

[0076] The graphene composite bullet-proof materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were composited with ultra-high molecular weight polyethylene to form a non-woven fabric and hot-pressed to form a bullet-proof insert. The ballistic performance test was performed. The results are shown in Table 1:

[0077] Tensile strength was measured using a universal tensile tester. Target shooting was conducted in accordance with the GA141-2010 standard, with reference to the requirement in GA141-2010, "Police Body Armor," that the impact of a projectile on a Level 2 body armor should not cause a dent greater than 25 mm in the cement backing. Mechanical properties: Tensile testing was performed at a speed of 500 mm / min using an MZ-4000D electronic universal testing machine, with reference to GB / T 528-2009. The median of five measurements was used for the test result.

[0078] Table 1 Graphene composite bulletproof material performance test results

[0079] project Example 1 Example 2 Example 33 Comparative Example 1 Comparative Example 2 Comparative Example 3 100% tensile strength (MPa) 17.5 18.3 19.8 9.8 8.5 9.6 Tensile strength (MPa) 37.98 38.59 39.51 21.26 19.32 20.41 Elongation at break (%) 720 729 738 623 612 619 Depression (mm) 9.01 8.96 8.85 23.98 24.56 24.12

[0080] As can be seen from Table 1, the graphene composite bullet-proof materials obtained in Examples 1 to 3 have significantly better 100% modulus, tensile strength, and elongation at break than the comparative example, and the degree of concavity is less than that of the comparative example, indicating that the graphene composite bullet-proof material prepared by the present invention has excellent strength, a small degree of concavity after being hit by a bullet, and can effectively cushion the impact force caused by the bullet.

[0081] In Comparative Example 1, PMMA microspheres coated with zinc oxide are replaced with PMMA microspheres as pyrolysis polymers. The PMMA microspheres coated with zinc oxide serve as a dispersed phase during the spinning and stretching process. Under the action of spinning tension, small balls are formed and covered on the polyacrylonitrile fiber precursor. During the pre-oxidation of polyacrylonitrile, the PMMA microspheres coated with zinc oxide are pyrolyzed to generate gas, thereby generating porous carbon fibers with uniform pores on the carbon fibers. The surface-coated zinc oxide nanospheres have a high thermal decomposition temperature and continue to exist on the surface of the carbon fibers. The high thermal conductivity of the zinc oxide nanospheres can improve the efficiency of pre-oxidation and avoid the problems of long reaction time, low efficiency and high production cost in the traditional pre-oxidation process. In addition, the existing zinc oxide nanospheres can serve as a reinforcing phase to improve the bulletproof strength of the porous carbon fibers. The presence of zinc oxide increases the surface roughness of the porous carbon fibers, which is beneficial to the coating of polypamine and provides sufficient active sites for the subsequent coating of graphene oxide.

[0082] In Comparative Example 2, the porous carbon fiber is replaced with conventional commercially available carbon fiber. PMMA microspheres coated with zinc oxide are used as pyrolysis polymers, and polyacrylonitrile is used as a carbon fiber precursor. The porous carbon fiber obtained by wet spinning has a rough and porous surface, which is different from the conventional commercially available smooth and inert carbon fiber. It is conducive to the subsequent coating of polydopamine and graphene oxide, and the surface porosity can increase the lightweight of the bulletproof vest.

[0083] In Comparative Example 3, the polydopamine-coated carbon fiber is replaced with porous carbon fiber. The polydopamine coating provides sufficient active sites for the subsequent graphene oxide coating, which is conducive to the uniform coating of graphene oxide, which is different from the weak interfacial bonding force caused by physical mixing in the comparative document.

[0084] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a graphene composite bulletproof material, characterized in that: The steps include: Step 1: zinc oxide nanospheres are treated with 3-aminopropyltriethoxysilane to obtain modified zinc oxide nanospheres with amino groups on the surface. PMMA microspheres are hydrolyzed under alkaline conditions to release carboxyl groups, and the modified zinc oxide nanospheres are grafted onto them through an amidation reaction to obtain zinc oxide-coated PMMA microspheres. Step 2: preparing polymer fiber precursors by a wet process from a spinning solution containing polyacrylonitrile and zinc oxide-coated PMMA microspheres, and then pre-oxidizing and carbonizing the precursors to obtain porous carbon fiber powder; Step 3: The porous carbon fiber powder is coated with polydopamine, and the amino group of the polydopamine undergoes an amidation reaction with the carboxyl group of the graphite oxide to obtain graphene oxide-coated carbon fiber; Step 4: The graphene oxide coated carbon fiber is treated with γ-methacryloxypropyltrimethoxysilane, and then the functionalized graphene oxide coated carbon fiber is mixed with phenolic resin and cured to obtain a graphene composite bulletproof material.

2. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the modified zinc oxide nanospheres are as follows: Zinc nitrate hexahydrate and deionized water are added to a reactor, stirred at 80-90°C and 500-600 r / min for 40-50 minutes, then ammonia water is added, stirring is continued until a white precipitate is produced, filtered, and washed to obtain zinc oxide nanospheres; zinc oxide nanospheres, anhydrous ethanol, and deionized water are added to a reactor, stirred at 60-70°C and 500-600 r / min for 10-15 minutes, then 3-aminopropyltriethoxysilane is added, the pH value is adjusted to 3-4 with hydrochloric acid solution, and the reaction is continued with stirring for 6-7 hours to obtain modified zinc oxide nanospheres; The usage ratio of zinc nitrate hexahydrate, deionized water and ammonia water is 70-80 g: 1-2 L: 80-90 mL; the usage ratio of zinc oxide nanospheres, anhydrous ethanol, deionized water and 3-aminopropyltriethoxysilane is 50-60 g: 1-2 L: 3-4 L: 100-120 mL.

3. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the zinc oxide-coated PMMA microspheres are as follows: Add PMMA microspheres and deionized water into a reactor, stir at 20-25°C and 500-600 r / min for 2-3 minutes, then add 0.05 g / mL NaOH solution, heat to 80-90°C, continue stirring for 12-14 hours, then add modified zinc oxide nanospheres and N,N'-dicyclohexylcarbodiimide, continue stirring for 6-7 hours, filter, and wash to obtain zinc oxide-coated PMMA microspheres.

4. The method for preparing a graphene composite bullet-proof material according to claim 3, wherein: The usage ratio of the PMMA microspheres, deionized water, NaOH solution, modified zinc oxide nanospheres and N,N'-dicyclohexylcarbodiimide is 15-20 g: 270-300 mL: 30-40 mL: 12-14 g: 10-12 g.

5. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the polymer fiber precursor are as follows: Polyacrylonitrile and N,N-dimethylformamide are added to a reactor in a ratio of 20-25 g:80-90 mL, and stirred at 60-70° C. and 500-600 r / min for 40-50 min to obtain a polyacrylonitrile dispersion; zinc oxide-coated PMMA microspheres and N,N-dimethylformamide are added to a reactor in a ratio of 5-6 g:20-30 mL, and stirred at 60-70° C. and 500-600 r / min for 40-50 min to obtain a zinc oxide-coated PMMA microsphere dispersion; the polyacrylonitrile dispersion and the zinc oxide-coated PMMA microsphere dispersion are stirred and mixed in a volume ratio of 3:1, and the mixture is placed in a vacuum oven at 50-60° C. for degassing for 30-40 min to obtain a spinning solution, which is then wet-spun to obtain polymer fiber precursors.

6. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the porous carbon fiber powder are as follows: The polymer fiber precursor is placed in a muffle furnace for pre-oxidation treatment, heated to 280-300°C at a heating rate of 5-6°C / min and kept warm for 20-30 minutes to obtain a pre-oxidized fiber precursor; the pre-oxidized fiber precursor is placed in a high-temperature carbonization furnace, and under nitrogen protection, heated to 380-400°C at a heating rate of 5-6°C / min, kept warm for 1-2 hours, heated to 450-500°C at a heating rate of 5-6°C / min, kept warm for 1-2 hours, heated to 900-1000°C at a heating rate of 1-2 hours, naturally cooled, crushed, and sieved to obtain a porous carbon fiber powder.

7. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the polydopamine coating are as follows: Adding Tris-HCl buffer with a pH value of 8.5, dopamine and porous carbon fiber powder into a reaction kettle, stirring at 30-40°C and 500-600 r / min for 15-16 hours, filtering, taking out the porous carbon fiber, washing, and vacuum drying to obtain polydopamine-coated carbon fiber; The usage ratio of the Tris-HCl buffer, dopamine and porous carbon fiber powder is 3-4L: 4-5g: 15-20g.

8. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the graphene oxide coated carbon fiber are as follows: Add graphene oxide, anhydrous ethanol and deionized water into a reactor, stir at 70-80°C and 500-600 r / min for 10-15 minutes, then add polydopamine-coated carbon fiber and N,N'-dicyclohexylcarbodiimide, continue stirring for 8-9 hours, filter, wash and vacuum dry to obtain graphene oxide-coated carbon fiber; The usage ratio of the graphene oxide, anhydrous ethanol, deionized water, polydopamine-coated carbon fiber and N,N'-dicyclohexylcarbodiimide is 15-20 g: 1-2 L: 3-4 L: 15-20 g.

9. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the functionalized graphene oxide coated carbon fiber are as follows: Adding graphene oxide-coated carbon fiber, anhydrous ethanol and deionized water into a reactor, stirring at 60-70°C and 500-600 r / min for 10-15 minutes, then adding γ-methacryloxypropyltrimethoxysilane, adjusting the pH value to 3-4 with hydrochloric acid solution, continuing to stir and react for 6-7 hours, filtering, washing, and vacuum drying to obtain functionalized graphene oxide-coated carbon fiber; The usage ratio of the graphene oxide-coated carbon fiber, anhydrous ethanol, deionized water and gamma-methacryloxypropyltrimethoxysilane is 20-30 g: 1-2 L: 3-4 L: 100-120 mL.

10. The method for preparing a graphene composite bullet-proof material according to claim 1, wherein: The specific preparation steps of the graphene composite bulletproof material are as follows: Functionalized graphene oxide-coated carbon fiber, polyethylene glycol and liquid phenolic resin are mixed uniformly in a dosage ratio of 15-20 g: 0.1-0.2 g: 80-90 g under the conditions of ultrasonic power of 400-500 W and shear speed of 2000-3000 r / min, dried to form a film, and cured to obtain a graphene composite bulletproof material.