Bulletproof composite material and preparation method thereof

Abstract

The invention discloses a bulletproof composite material preparation method, which comprises: reacting hydroxyl-terminated silicone oil with boric acid to synthesize polyborosiloxane, carrying out vacuum dehydration, and adding hydroxyl silicone oil to obtain a liquid polyborosiloxane modification auxiliary agent; the preparation method comprises the following steps: reacting polycarbonate diol, diphenylmethane diisocyanate, a liquid polyborosiloxane modification additive and acetone to obtain a polyborosiloxane modified polyurethane prepolymer; adding dimethylolpropionic acid, a catalyst, surface modified nano silicon dioxide, acetone, a small molecule chain extender and a neutralizer into the prepolymer, and dispersing and emulsifying with water to obtain a polyborosiloxane modified waterborne polyurethane emulsion; the preparation method comprises the following steps: compounding UHMWPE (Ultra High Molecular Weight Polyethylene) fibers and waterborne polyurethane to obtain PEUD prepreg; the PEUD prepreg is subjected to high-temperature pressing through a flat plate molding press, and the bulletproof composite material is obtained; the bulletproof composite material provided by the invention solves the problems in the aspects of energy dissipation mechanism, environmental friendliness, functionality and the like of the traditional bulletproof composite material, and has the characteristics of light weight, high strength, high impact resistance and strain rate sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of safety protection technology, specifically relating to a bulletproof composite material and its preparation method. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) composites can absorb up to 2.6 times the total energy of impact compared to aramid and 1.8 times that of carbon fiber. With its extreme lightweight, high strength, and excellent energy absorption characteristics, UHMWPE has become an indispensable key material in modern protective applications. The friction between UHMWPE fibers is weak, and the absence of yarn interlacing points in the UD (Ultra-High Molecular Weight) non-woven fabric structure eliminates fiber buckling, thus eliminating negative effects such as stress wave reflection and superposition at yarn crossover points. Shock waves propagate further along the fiber axis, fully utilizing the extreme strength and modulus of UHMWPE fibers in the axial direction, achieving the most efficient energy dispersion and absorption. Compared to plain weave fabrics and three-dimensional fabrics, the orthogonal UD structure has the best ballistic protection performance; therefore, UHMWPE fibers are primarily used in the form of UD fabric for ballistic protection products.

[0003] Waterborne polyurethane (WPU) is non-toxic and has a low content of volatile organic compounds (VOCs). It typically has lower viscosity and better flowability, allowing it to penetrate fiber fabrics more quickly and uniformly compared to thermosetting resins such as epoxy and phenolic resins. Most thermosetting resins, such as epoxy resins, have higher viscosity, making it difficult to quickly penetrate the dense PE fiber bundles. This results in poor wettability, high curing stress, and high shrinkage after curing, leading to significant internal stress. Furthermore, the brittle matrix of epoxy resins cannot effectively transfer energy upon impact. In contrast, the excellent adhesion and flexible matrix of waterborne polyurethane allow impact energy to be transferred and dissipated more effectively between fibers, fully utilizing the high performance of UHMWPE fibers. Therefore, waterborne polyurethane is widely used in the preparation of UHMWPE fiber UD nonwoven fabrics. However, ordinary waterborne polyurethane, due to insufficient matrix strength and modulus, lacks support. Low-modulus thermoplastic resin laminates can exhibit significant lateral deformation upon impact, forming a back convexity and affecting protective performance. Furthermore, the fiber-resin interface is weak, resulting in severe delamination failure, and the fiber and resin are prone to interfacial peeling upon impact.

[0004] The Chinese invention patent CN115847977A, entitled "A Nanofiller Reinforced Fiber Hybrid Structure Bulletproof Composite Material and Preparation Method", proposes a method for modifying waterborne polyurethane with nanofillers and adding silane coupling agents to improve its compatibility. This method helps to improve the mechanical properties of waterborne polyurethane to a certain extent. When the areal density is 6 kg / m2, the V50 is 650 m / s. However, it does not mention the BFS indentation performance data and does not fully explain the long-term dispersion stability of graphene oxide in the system and the interfacial stability with the polymer matrix. The invention patent CN115960462A, entitled "A Reinforcing Additive Modified UHMWPE UD Prepreg and Its Application," mentions the use of a reinforcing additive containing polyborosiloxane, added to an aqueous polyurethane emulsion in the form of physical blending, to modify the composite material and improve its dent resistance. However, the molecular structure and chemical properties of polyborosiloxane differ significantly from those of the polyurethane matrix. Therefore, under long-term service conditions, macroscopic phase separation, or even failure, is highly likely due to poor compatibility. Furthermore, the patent lacks verification regarding compatibility and performance durability. Therefore, developing a novel modified aqueous polyurethane with stable performance that can significantly improve its modulus, strength, interfacial adhesion, and protective properties is crucial for promoting the development of a new generation of high-performance, intelligent bulletproof composite materials. Summary of the Invention

[0005] To overcome the problem of poor compatibility between polyborosiloxane and polyurethane, this invention provides a bulletproof composite material and its preparation method. First, a prepolymerized polyborosiloxane with a lower degree of reaction (condensation degree) than traditional semi-solid polyborosiloxane is prepared. This polyborosiloxane is liquid and retains more unreacted hydroxyl groups. It is then used in a pre-condensation reaction with isocyanate and polyol, directly embedding polyborosiloxane segments into the soft segments of polyurethane to form a chemically modified waterborne polyurethane. Surface-modified nano-silica is then combined to improve the adhesion of the waterborne polyurethane. After modification, the waterborne polyurethane is composited with UHMWPE fibers. Subsequent heat treatment yields a bulletproof composite material with excellent strength, anti-delamination ability, and impact resistance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A bulletproof composite material comprises two parts: UHMWPE fiber and polyborosiloxane-modified waterborne polyurethane. The polyborosiloxane-modified waterborne polyurethane contains the following raw materials in parts by weight: 56-64 parts of polycarbonate diol, 2-8 parts of liquid polyborosiloxane modifying agent, 0.5-2 parts of surface-modified nano-silica, 20-30 parts of diphenylmethane diisocyanate, 2-6 parts of dimethylolpropionic acid, 0.5-3 parts of small molecule chain extender, 1.5-5 parts of neutralizing agent, 0.05-0.07 parts of catalyst, and 25 parts of acetone.

[0008] A method for preparing a bulletproof composite material specifically includes the following steps:

[0009] Step 1, preparing the polyborosiloxane modified additive, the specific steps are as follows:

[0010] Hydroxyl-terminated silicone oil was added to the reactor and stirred continuously. The temperature was raised to 90°C, and then boric acid was added to react. The temperature was then raised to 120°C and kept at that temperature for 1 hour to synthesize polyborosiloxane.

[0011] The obtained polyborosiloxane was vacuum-heated to 80°C, dehydrated under vacuum, and then hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane was added. After the reaction was kept at the temperature for 1 hour, liquid polyborosiloxane modified additive was obtained.

[0012] Step 2, prepare the polyborosiloxane-modified waterborne polyurethane emulsion, the specific steps are as follows:

[0013] N2 was introduced into a three-necked round-bottom flask and polycarbonate diol, diphenylmethane diisocyanate, the liquid polyborosiloxane modifier prepared in step 1, and acetone were added. The mixture was stirred and reacted at 80-90℃ to obtain polyborosiloxane modified polyurethane prepolymer.

[0014] Cool the temperature to 50℃ ~ 65℃, add dimethylolpropionic acid, catalyst, surface-modified nano silica and acetone to the polyborosiloxane modified polyurethane prepolymer, continue the reaction for 1~2h, then add a small molecule chain extender and continue the chain extension reaction for 0.5~1h.

[0015] Add a neutralizing agent and react for 10 to 20 minutes. Then, under high-speed stirring, add deionized water to disperse and emulsify the mixture to obtain a crude emulsion.

[0016] The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0017] Step 3: The UHMWPE fibers are evenly spread and immersed in the polyborosiloxane-modified waterborne polyurethane emulsion prepared in Step 2 using a fiber spreader. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven to dry, thus obtaining PEUD prepreg.

[0018] Step 4: The PEUD prepreg obtained in Step 3 is uniformly cut into 300*300mm sheets, and after being laid up at [0° / 90°], it is pressed at high temperature by a flatbed molding machine to obtain the bulletproof composite material.

[0019] Furthermore, in step 1, the molar ratio of silicon atoms to boron atoms in the polyborosiloxane is 15.1:1 to 5.3:1.

[0020] Furthermore, in step 1, the weight ratio of polyborosiloxane to hydroxyl silicone oil is 1:1.

[0021] Further, the preparation steps of the surface-modified nano silica in step 2 are as follows: dissolve nano silica in anhydrous ethanol solution, disperse it by ultrasonication for 0.5 h, add γ-(methacryloyloxy)propyltrimethoxysilane dropwise, the mass ratio of nano silica to γ-(methacryloyloxy)propyltrimethoxysilane is 5:1, react at 60-70℃ for 2 hours, remove unreacted γ-(methacryloyloxy)propyltrimethoxysilane, and then vacuum dry at 80℃ to obtain surface-modified nano silica, wherein the diameter of the surface-modified nano silica is less than 10 nm.

[0022] Furthermore, the catalyst in step 2 is any one of organobismuth and organotin catalysts, the small molecule chain extender is one or more of 1,4-butanediol, diethylene glycol, ethylene glycol, and trimethylolpropane, and the neutralizing agent is any one of triethylamine, ammonia, and N-methyldiethanolamine.

[0023] Furthermore, in step 2, the high-speed stirring speed is ≥1000 rpm.

[0024] Furthermore, the solid content in the polyborosiloxane-modified waterborne polyurethane emulsion prepared in step 2 is 20% to 40%.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention modifies waterborne polyurethane with polyborosiloxane. The dynamic borate ester bonds (BO bonds) in the polyborosiloxane undergo reversible breakage and recombination under high-speed impact. This breakage of dynamic chemical bonds is an active, energy-consuming process that effectively dissipates impact energy, thereby reducing the energy transferred to the main fibers and preventing premature and catastrophic fiber breakage. Simultaneously, the addition of nano-silica effectively improves the mechanical strength of the resin matrix and enhances the interlayer bonding strength of the composite material. This invention solves multiple problems in energy dissipation mechanisms, environmental friendliness, and functionality of traditional bulletproof composite materials, providing a lightweight, high-strength, high-impact-resistant bulletproof composite material with strain rate-sensitive properties. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to specific embodiments.

[0028] This invention provides a bulletproof composite material comprising two parts: UHMWPE fiber and polyborosiloxane-modified waterborne polyurethane. The polyborosiloxane-modified waterborne polyurethane contains the following raw materials in parts by weight: 56-64 parts of polycarbonate diol, 2-8 parts of liquid polyborosiloxane modifying agent, 0.5-2 parts of surface-modified nano-silica, 20-30 parts of diphenylmethane diisocyanate, 2-6 parts of dimethylolpropionic acid, 0.5-3 parts of small molecule chain extender, 1.5-5 parts of neutralizing agent, 0.05-0.07 parts of catalyst, and 25 parts of acetone.

[0029] A method for preparing a bulletproof composite material specifically includes the following steps:

[0030] Step 1, preparing the polyborosiloxane modified additive, the specific steps are as follows:

[0031] Hydroxyl-terminated silicone oil was added to the reactor and stirred continuously. The temperature was raised to 90°C, and then boric acid was added to react. The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in polyborosiloxane is 15.1:1 to 5.3:1).

[0032] The obtained polyborosiloxane was vacuum-heated to 80°C, and after vacuum dehydration, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added. After the reaction was kept at the temperature for 1 hour, liquid polyborosiloxane modified additive was obtained.

[0033] Step 2, prepare the polyborosiloxane-modified waterborne polyurethane emulsion, the specific steps are as follows:

[0034] N2 was introduced into a three-necked round-bottom flask and polycarbonate diol, diphenylmethane diisocyanate, the liquid polyborosiloxane modifier prepared in step 1, and acetone were added. The mixture was stirred and reacted at 80-90℃ to obtain polyborosiloxane modified polyurethane prepolymer.

[0035] Cool the temperature to 50℃ ~ 65℃, add dimethylolpropionic acid, catalyst (any one of organobismuth and organotin catalysts), surface-modified nano-silica, and acetone to the polyborosiloxane-modified polyurethane prepolymer, and continue the reaction for 1~2 hours. Then, further add a small molecule chain extender (one or more of 1,4-butanediol, diethylene glycol, ethylene glycol, and trimethylolpropane) and continue the chain extension reaction for 0.5~1 hours.

[0036] Add a neutralizing agent (any one of triethylamine, ammonia, and N-methyldiethanolamine), react for 10-20 minutes under high-speed shear stirring, and then add deionized water under high-speed stirring (high-speed stirring speed ≥1000 rpm) to disperse and emulsify, to obtain a crude emulsion;

[0037] The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion (the solid content in the polyborosiloxane-modified waterborne polyurethane emulsion was 20% to 40%).

[0038] The preparation steps of surface-modified nano-silica are as follows: nano-silica is dissolved in anhydrous ethanol solution, ultrasonically dispersed for 0.5 h, and γ-(methacryloyloxy)propyltrimethoxysilane is added dropwise. The mass ratio of nano-silica to γ-(methacryloyloxy)propyltrimethoxysilane is 5:1. The reaction is carried out at 60-70℃ for 2 hours. Unreacted γ-(methacryloyloxy)propyltrimethoxysilane is removed, and then vacuum dried at 80℃ to obtain surface-modified nano-silica. The diameter of the surface-modified nano-silica is less than 10 nm.

[0039] Step 3: The UHMWPE fibers are evenly spread and immersed in the polyborosiloxane-modified waterborne polyurethane emulsion prepared in Step 2 using a fiber spreader. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven to dry, thus obtaining PEUD prepreg.

[0040] Step 4: The PEUD prepreg obtained in Step 3 is uniformly cut into 300*300mm sheets, and after being laid up at [0° / 90°], it is pressed at high temperature by a flatbed molding machine to obtain the bulletproof composite material.

[0041] Example 1

[0042] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0043] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel and stirred continuously. The temperature was raised to 90°C, and then boric acid was added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 1:1). The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 7.1:1). The obtained polyborosiloxane was taken, heated to 80°C under vacuum, and dehydrated under vacuum. Then, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added and the reaction was held for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0044] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0045] In a dry 500 mL three-necked round-bottom flask under nitrogen protection, 60 parts of polycarbonate diol, 25 parts of diphenylmethane diisocyanate, 4 parts of liquid polyborosiloxane modifying agent, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a polyborosiloxane-modified polyurethane prepolymer. The temperature was lowered to 65 °C, and 4 parts of dimethylolpropionic acid, 0.06 parts of bismuth isooctanoate, 1 part of dry surface-modified nano-silica, and 10 parts of acetone were added to the polyborosiloxane-modified polyurethane prepolymer. The reaction was continued for 2 hours. Subsequently, 1.5 parts of 1,4-butanediol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 3.1 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0046] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0047] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0048] Example 2

[0049] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0050] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel and stirred continuously. The temperature was raised to 90°C, and then boric acid was added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 1:1). The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 7.1:1). The obtained polyborosiloxane was taken, heated to 80°C under vacuum, and dehydrated under vacuum. Then, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added and the reaction was held for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0051] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0052] In a dry 500 mL three-necked flask under nitrogen protection, 58 parts of polycarbonate diol, 20 parts of diphenylmethane diisocyanate, 6 parts of liquid polyborosiloxane modifier, and 15 parts of acetone were added. The mixture was reacted at 85 °C for 4 hours to obtain a polyborosiloxane-modified polyurethane prepolymer. The temperature was lowered to 60 °C, and 4 parts of dimethylolpropionic acid, 0.06 parts of bismuth isooctanoate, 1.5 parts of dry surface-modified nano-silica, and 10 parts of acetone were added to the polyborosiloxane-modified polyurethane prepolymer. The reaction was continued for 2 hours. Subsequently, 1.5 parts of 1,4-butanediol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 3.1 parts of ammonia water were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0053] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0054] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0055] Example 3

[0056] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0057] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel and stirred continuously. The temperature was raised to 90°C, and then boric acid was added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 1:1). The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 7.1:1). The obtained polyborosiloxane was taken, heated to 80°C under vacuum, and dehydrated under vacuum. Then, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added and the reaction was held for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0058] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0059] In a dry 500 mL three-necked flask under nitrogen protection, 56 parts of polycarbonate diol, 20 parts of diphenylmethane diisocyanate, 8 parts of liquid polyborosiloxane modifying agent, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a polyborosiloxane-modified polyurethane prepolymer. The temperature was lowered to 50 °C, and 4 parts of dimethylolpropionic acid, 0.07 parts of bismuth isooctanoate, 1 part of dry surface-modified nano-silica, and 10 parts of acetone were added to the polyborosiloxane-modified polyurethane prepolymer. The reaction was continued for 2 hours. Subsequently, 3 parts of diethylene glycol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 1.5 parts of N-methyldiethanolamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified under high-speed shear at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0060] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0061] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0062] Example 4

[0063] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0064] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel and stirred continuously. The temperature was raised to 90°C, and then boric acid was added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 1:1). The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 7.1:1). The obtained polyborosiloxane was taken, heated to 80°C under vacuum, and dehydrated under vacuum. Then, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added and the reaction was held for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0065] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0066] In a dry 500 mL three-necked flask under nitrogen protection, 64 parts of polycarbonate diol, 30 parts of diphenylmethane diisocyanate, 2 parts of liquid polyborosiloxane modifier, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a polyborosiloxane-modified polyurethane prepolymer. The temperature was lowered to 65 °C, and 2 parts of dimethylolpropionic acid, 0.05 parts of bismuth isooctanoate, 2 parts of dried surface-modified nano-silica, and 10 parts of acetone were added to the polyborosiloxane-modified polyurethane prepolymer. The reaction was continued for 2 hours. Subsequently, 0.5 parts of ethylene glycol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 1.5 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0067] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0068] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0069] Example 5

[0070] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0071] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel and stirred continuously. The temperature was raised to 90°C, and then boric acid was added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 1:1). The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 7.1:1). The obtained polyborosiloxane was taken, heated to 80°C under vacuum, and dehydrated under vacuum. Then, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added and the reaction was held for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0072] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0073] In a dry 500 mL three-necked flask under nitrogen protection, 56 parts of polycarbonate diol, 20 parts of diphenylmethane diisocyanate, 8 parts of liquid polyborosiloxane modifier, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a polyborosiloxane-modified polyurethane prepolymer. The temperature was lowered to 65 °C, and 6 parts of dimethylolpropionic acid, 0.05 parts of bismuth isooctanoate, 0.5 parts of dried surface-modified nano-silica, and 10 parts of acetone were added to the polyborosiloxane-modified polyurethane prepolymer. The reaction was continued for 2 hours. Subsequently, 1.5 parts of trimethylolpropane were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 5 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0074] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0075] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0076] Example 6

[0077] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0078] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel, stirred continuously, and heated to 90°C. Boric acid was then added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 2:1). The temperature was further increased to 120°C and maintained for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 15.1:1). The obtained polyborosiloxane was taken, heated under vacuum to 80°C, and dehydrated under vacuum. Hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added, and the reaction was maintained for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0079] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0080] In a dry 500 mL three-necked flask under nitrogen protection, 56 parts of polycarbonate diol, 20 parts of diphenylmethane diisocyanate, 8 parts of liquid polyborosiloxane modifier, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a prepolymer. The temperature was lowered to 65 °C, and 4 parts of dimethylolpropionic acid, 0.05 parts of bismuth isooctanoate, 1 part of dry nano-silica, and 10 parts of acetone were added, and the reaction was continued for 2 hours. Subsequently, 1.5 parts of 1,4-butanediol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 3.1 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified under high-speed shear at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0081] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0082] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0083] Example 7

[0084] Step 1, Preparation of liquid polyborosiloxane modified additive:

[0085] Hydroxyl-terminated silicone oil (hydroxyl value 9.2%) was added to a reaction vessel and stirred continuously. The temperature was raised to 90°C, and then boric acid was added (hydroxyl-terminated silicone oil and boric acid were added at a hydroxyl ratio of 1:2). The temperature was further raised to 120°C and held for 1 hour to synthesize polyborosiloxane (the molar ratio of silicon atoms to boron atoms in the polyborosiloxane was 5.3:1). The obtained polyborosiloxane was taken, heated to 80°C under vacuum, and dehydrated under vacuum. Then, hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane (the weight ratio of polyborosiloxane to hydroxyl silicone oil was 1:1) was added and the reaction was held for 1 hour to obtain liquid polyborosiloxane modifying agent.

[0086] Step 2, Preparation of polyborosiloxane-modified waterborne polyurethane emulsion:

[0087] In a dry 500 mL three-necked flask under nitrogen protection, 56 parts of polycarbonate diol, 20 parts of diphenylmethane diisocyanate, 8 parts of liquid polyborosiloxane modifier, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a prepolymer. The temperature was lowered to 65 °C, and 4 parts of dimethylolpropionic acid, 0.05 parts of bismuth isooctanoate, 1 part of dry nano-silica, and 10 parts of acetone were added, and the reaction was continued for 2 hours. Subsequently, 1.5 parts of 1,4-butanediol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 3.1 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified under high-speed shear at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion.

[0088] Step 3: The UHMWPE fibers are evenly spread and impregnated in the polyborosiloxane-modified waterborne polyurethane emulsion on a spinning machine. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce PEUD prepreg.

[0089] Step 4: After cutting a sufficient amount of prepreg into 300mm*300mm sheets, stack them according to [0° / 90°], and mold them at 15MPa pressure and 120℃ for 25min to prepare a bulletproof composite material with a thickness of 8mm.

[0090] Comparative Example 1

[0091] Preparation of modified waterborne polyurethane emulsion:

[0092] In a dry 500 mL three-necked flask under nitrogen protection, 64 parts of polycarbonate diol, 25 parts of diphenylmethane diisocyanate, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a prepolymer. The temperature was lowered to 65 °C, and 4 parts of dimethylolpropionic acid, 0.06 parts of bismuth isooctanoate, 1 part of dry nano-silica, and 10 parts of acetone were added, reacting for 2 hours. Then, 1.5 parts of 1,4-butanediol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 3.1 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding an aqueous polyurethane emulsion.

[0093] UHMWPE fibers are evenly spread in an aqueous polyurethane emulsion using a spinning machine. The UHMWPE fibers impregnated with the aqueous polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce a prepreg.

[0094] After cutting a sufficient amount of prepreg into 300mm*300mm sheets, they were stacked in [0° / 90°] and molded at 15MPa pressure and 120℃ for 25min to prepare a composite material with a thickness of 8mm.

[0095] The difference between Comparative Example 1 and Example 1 is that liquid polyborosiloxane is not added to the raw materials for preparing the waterborne polyurethane emulsion, and the 4 parts are made up by 4 parts of polycarbonate diol.

[0096] Comparative Example 2

[0097] Preparation of modified waterborne polyurethane emulsion:

[0098] In a dry 500 mL three-necked flask under nitrogen protection, 64 parts of polycarbonate diol, 25 parts of diphenylmethane diisocyanate, 4 parts of polyborosiloxane modifier, and 15 parts of acetone were added. The mixture was reacted at 80 °C for 4 hours to obtain a prepolymer. The temperature was lowered to 65 °C, and 4 parts of dimethylolpropionic acid, 0.06 parts of bismuth isooctanoate, and 10 parts of acetone were added, reacting for 2 hours. Then, 1.5 parts of 1,4-butanediol were added, and the reaction was continued for 1 hour. The temperature was lowered to 35 °C, and 3.1 parts of triethylamine were added for neutralization for 10 minutes. Deionized water was added, and the mixture was emulsified at 1200 rpm for 20 minutes to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding an aqueous polyurethane emulsion.

[0099] UHMWPE fibers are evenly spread in an aqueous polyurethane emulsion using a spinning machine. The UHMWPE fibers impregnated with the aqueous polyurethane emulsion are then guided into an oven and dried at 80°C for 10 minutes to produce a prepreg.

[0100] After cutting a sufficient amount of prepreg into 300mm*300mm sheets, they were stacked in [0° / 90°] and molded at 15MPa pressure and 120℃ for 25min to prepare a composite material with a thickness of 8mm.

[0101] The difference between Comparative Example 2 and Example 1 is that the raw materials for preparing waterborne polyurethane do not contain liquid polyborosiloxane and surface-modified nano silica, and the amount of 4 parts of liquid polyborosiloxane is made up by 4 parts of polycarbonate diol.

[0102] Mechanical property testing

[0103] The modified waterborne polyurethanes synthesized in Examples 1-7 and Comparative Examples 1-2 were prepared into films in a vacuum dryer, and their tensile strength and elongation at break were tested according to GB / T 528-2009 standard. The peel strength was tested according to GB / T2791 "Adhesives T Peel Strength Test Method Flexible Materials to Flexible Materials". The adhesive material was UHMWPE fiber woven fabric. The mechanical property test results are shown in Table 1.

[0104] Table 1 Comparison of mechanical properties between Examples 1-7 and Comparative Examples 1-2

[0105]

[0106] The composite material samples of Examples 1-7 and Comparative Examples 1-2 were subjected to V50 ballistic resistance test and dent resistance test according to GA141 standard. The results are shown in Table 2.

[0107] Table 2 Comparison of V50 performance and dent resistance between Examples 1-7 and Comparative Examples 1-2

[0108]

[0109] As shown in Tables 1-2, the strength of the resin matrix obtained in all embodiments of the present invention was improved, and the interlaminar shear peel strength was significantly higher than that of the two comparative examples. This indicates that the interfacial bonding between the modified waterborne polyurethane and UHMWPE fibers was greatly improved, attributed to the resin's flexibility and excellent wettability. The bulletproof composite material prepared by waterborne polyurethane modified with polyborosiloxane and nano-silica exhibits superior impact resistance compared to ordinary waterborne polyurethane. This proves that the bulletproof composite material successfully prepared by the present invention through the introduction of liquid polyborosiloxane modifiers with specific structures and ratios and surface-modified nano-silica has achieved significant improvements over traditional technologies in terms of matrix strength, bonding performance, ballistic performance, and dent resistance, fully realizing the expected beneficial effects of the present invention.

[0110] The above description of the present invention represents only some embodiments, but the present invention is not limited to the above embodiments. The above embodiments are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.

Claims

1. A bulletproof composite material, characterized in that, It consists of two parts: UHMWPE fiber and polyborosiloxane-modified waterborne polyurethane. The polyborosiloxane-modified waterborne polyurethane contains the following raw materials in parts by weight: 56-64 parts of polycarbonate diol, 2-8 parts of liquid polyborosiloxane modifying agent, 0.5-2 parts of surface-modified nano silica, 20-30 parts of diphenylmethane diisocyanate, 2-6 parts of dimethylolpropionic acid, 0.5-3 parts of small molecule chain extender, 1.5-5 parts of neutralizing agent, 0.05-0.07 parts of catalyst, and 25 parts of acetone.

2. The method for preparing a bulletproof composite material according to claim 1, characterized in that, Specifically, the following steps are included: Step 1, preparing the polyborosiloxane modified additive, the specific steps are as follows: Hydroxyl-terminated silicone oil was added to the reactor and stirred continuously. The temperature was raised to 90°C, and then boric acid was added to react. The temperature was then raised to 120°C and kept at that temperature for 1 hour to synthesize polyborosiloxane. The obtained polyborosiloxane was vacuum-heated to 80°C, dehydrated under vacuum, and then hydroxyl silicone oil with the same hydroxyl value as the polyborosiloxane was added. After the reaction was kept at the temperature for 1 hour, liquid polyborosiloxane modified additive was obtained. Step 2, prepare the polyborosiloxane-modified waterborne polyurethane emulsion, the specific steps are as follows: N2 was introduced into a three-necked round-bottom flask and polycarbonate diol, diphenylmethane diisocyanate, the liquid polyborosiloxane modifier prepared in step 1, and acetone were added. The mixture was stirred and reacted at 80-90℃ to obtain polyborosiloxane modified polyurethane prepolymer. Cool the temperature to 50℃ ~ 65℃, add dimethylolpropionic acid, catalyst, surface-modified nano silica and acetone to the polyborosiloxane modified polyurethane prepolymer, continue the reaction for 1~2h, then add a small molecule chain extender and continue the chain extension reaction for 0.5~1h. Add a neutralizing agent and react for 10 to 20 minutes. Then, under high-speed stirring, add deionized water to disperse and emulsify the mixture to obtain a crude emulsion. The crude emulsion was subjected to vacuum distillation to remove acetone, yielding a stable polyborosiloxane-modified waterborne polyurethane emulsion. Step 3: The UHMWPE fibers are evenly spread and immersed in the polyborosiloxane-modified waterborne polyurethane emulsion prepared in Step 2 using a fiber spreader. The UHMWPE fibers impregnated with the polyborosiloxane-modified waterborne polyurethane emulsion are then guided into an oven to dry, thus obtaining PEUD prepreg. Step 4: The PEUD prepreg obtained in Step 3 is uniformly cut into 300*300mm sheets, and after being laid up at [0° / 90°], it is pressed at high temperature by a flatbed molding machine to obtain the bulletproof composite material.

3. The method for preparing a bulletproof composite material according to claim 2, characterized in that, In step 1, the molar ratio of silicon atoms to boron atoms in the polyborosiloxane is 15.1:1 to 5.3:

1.

4. The method for preparing a bulletproof composite material according to claim 2, characterized in that, In step 1, the weight ratio of polyborosiloxane to hydroxyl silicone oil is 1:

1.

5. The method for preparing a bulletproof composite material according to claim 2, characterized in that, The preparation steps of the surface-modified nano silica in step 2 are as follows: dissolve nano silica in anhydrous ethanol solution, disperse it by ultrasonication for 0.5 h, add γ-(methacryloyloxy)propyltrimethoxysilane dropwise, the mass ratio of nano silica to γ-(methacryloyloxy)propyltrimethoxysilane is 5:1, react at 60-70℃ for 2 hours, remove unreacted γ-(methacryloyloxy)propyltrimethoxysilane, and then vacuum dry at 80℃ to obtain surface-modified nano silica with a diameter of less than 10 nm.

6. The method for preparing a bulletproof composite material according to claim 2, characterized in that, The catalyst mentioned in step 2 is any one of organobismuth and organotin catalysts, the small molecule chain extender is one or more of 1,4-butanediol, diethylene glycol, ethylene glycol, and trimethylolpropane, and the neutralizing agent is any one of triethylamine, ammonia, and N-methyldiethanolamine.

7. The method for preparing a bulletproof composite material according to claim 2, characterized in that, In step 2, the high-speed stirring speed is ≥1000 rpm.

8. The method for preparing a bulletproof composite material according to claim 2, characterized in that, The solid content in the polyborosiloxane-modified waterborne polyurethane emulsion prepared in step 2 is 20% to 40%.

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