Bulletproof material based on polymer composite material and preparation method of bulletproof material

Abstract

The invention relates to the field of material science and engineering, and particularly discloses a preparation method of a bulletproof material based on a polymer composite material. The bulletproof material is formed by compounding a modified ultra-high molecular weight polyethylene fiber fabric with the surface grafted with pyridyl silane and a force-chemical response polyurea matrix. The polyurea matrix is obtained by reacting and curing an isocyanate prepolymer and a component containing a functional chain extender triborane and a latent monomer bisphenol A cyanate ester. According to the invention, boron-nitrogen coordination is utilized to construct a catalyst capped system, coordination bonds are broken under the high-energy action of ballistic impact to release active boron, and a latent monomer is catalyzed to generate in-situ chemical curing; meanwhile, the strong Lewis alkalinity of pyridine groups on the surfaces of the fibers is utilized to induce a boron center in the resin to migrate to an interface and form coordination anchoring, so that the shear slippage resistance is improved. The flexible bulletproof material effectively solves the technical problem that the anti-sinking performance and the anti-penetrating performance of the flexible bulletproof material are difficult to consider under the light weight condition.

Description

Technical Field

[0001] This application relates to the field of materials science and engineering, and more specifically, to silicon carbide reinforced perfluoroether rubber high-temperature thermally conductive sealing composite materials and their preparation process. Background Technology

[0002] As individual soldier protective equipment evolves towards lighter weight, greater comfort, and higher performance, high-performance fiber-reinforced composite materials have become the mainstream choice for modern ballistic armor and lightweight ballistic plates. Among them, ultra-high molecular weight polyethylene fiber, with its low density, high modulus, and high specific strength, occupies a core position in the field of ballistic protection. However, while pursuing ultimate lightweighting, effectively controlling the back indentation depth of ballistic materials under high-speed projectile impact and preventing non-penetrating blunt force trauma remains a critical technical bottleneck that urgently needs to be addressed in this field.

[0003] While ultra-high molecular weight polyethylene (UHMWPE) fiber is the mainstream material for lightweight protection, its weak interfacial adhesion to the matrix due to surface chemical inertness makes it prone to fiber slippage and windowing effects under ballistic impact, severely limiting ballistic protection performance. Existing surface modification methods mostly provide weak physical anchoring, which is insufficient to resist high-energy shear. While introducing shear thickening liquids containing high-density inorganic particles can suppress slippage, it inevitably increases the areal density significantly and causes stability problems such as particle agglomeration and sedimentation, sacrificing the lightweight advantage of the equipment. In addition, the conventional resin matrix used in existing ballistic composite materials usually exhibits constant viscoelasticity and cannot undergo a sudden modulus change from soft to stiff at the moment of impact, making it difficult to effectively control back indentation. Furthermore, existing reinforcement methods often come at the cost of wearing comfort. Therefore, there is an urgent need to develop a smart protective material that does not require heavy fillers, can solve the interfacial slippage problem through chemical bonding, and can achieve impact-induced in-situ chemical hardening, thus balancing lightweight, comfort, and high protective performance. Summary of the Invention

[0004] To address the challenge of achieving both dent resistance and penetration resistance in existing flexible bulletproof materials while maintaining lightweight properties, this application provides a silicon carbide-reinforced perfluoroether rubber high-temperature thermally conductive sealing composite material and its preparation process.

[0005] In a first aspect, the present invention provides a bulletproof material based on a polymer composite material.

[0006] The bulletproof material is composed of a modified ultra-high molecular weight polyethylene fiber fabric and a mechanochemically responsive polyurea matrix impregnated between its layers.

[0007] The mechanochemically responsive polyurea matrix is ​​a product formed by the reaction and curing of component A and component B at an isocyanate index of 1.05 to 1.10, and unreacted latent monomers are dispersed in the matrix.

[0008] Component A contains an isocyanate-terminated prepolymer generated by reacting diphenylmethane diisocyanate with an amino-terminated polyether.

[0009] Component B comprises an amino-terminated polyether, triborane as a functionalized chain extender serving as a Lewis acid source, and bisphenol A cyanate as a latent monomer.

[0010] The modified ultra-high molecular weight polyethylene fiber fabric has a hydrolytic condensate derived from the interface modifier 3-thiopropyltrimethoxysilane grafted onto its surface. The Lewis basicity of the pyridine group provided by the interface modifier is stronger than that of the urea nitrogen atom in the polyurea matrix.

[0011] The composition of component B, by mass percentage, is as follows: 69.0%–82.0% terminal amino polyether, 3.0%–6.0% functionalized chain extender triborane, and 15.0%–25.0% latent monomer bisphenol A cyanate. In this system, the electron-deficient boron center in the functionalized chain extender pre-forms a B←N coordination bond with the electron-rich amino nitrogen atom in the terminal amino polyether, thereby masking the catalytic activity of the boron atom and rendering it inactive; while the latent monomer bisphenol A cyanate is stably dispersed in the polyurea network in the form of physical blending.

[0012] When ballistic protective materials are subjected to high-speed ballistic impact, the polyurea matrix undergoes violent deformation, forcing the weaker B←N coordination bonds to break first in order to dissipate energy. Simultaneously with the breakage of the B←N bonds, boron atoms, previously locked in a nitrogen complex, are instantly exposed, regaining their strong Lewis acid catalytic activity. The exposed boron atoms rapidly catalyze the in-situ polymerization of surrounding dispersed latent monomers, leading to a transient chemical hardening of the matrix at the impact point. This millisecond-level transition from a flexible to a rigid state significantly increases the material's modulus, thereby effectively suppressing back indentation.

[0013] In a second aspect, the present invention provides a method for preparing a bulletproof material based on a polymer composite material.

[0014] The method includes the following steps:

[0015] Step S1: Surface treatment of ultra-high molecular weight polyethylene fiber fabric is performed by grafting interface modifier 3-thiopropyltrimethoxysilane to obtain modified fiber fabric with strong Lewis basic sites on the surface.

[0016] Step S2: Prepare component A and component B. Component A is an isocyanate prepolymer; component B is prepared by premixing the functionalized chain extender triborane with an amino-terminated polyether to form a coordination structure between boron atoms and amino nitrogen atoms, and then adding the latent monomer bisphenol A cyanate for dispersion to ensure that the catalyst is in a caged state and the monomer is in a latent state.

[0017] Step S3: Mix component A and component B, and then coat them evenly on the surface of the modified fiber fabric to obtain a prepreg.

[0018] Step S4: Heat-treat the prepreg at 95~110℃ for 5~8 minutes to induce the boron centers in the resin to migrate and coordinate to the pyridine groups on the fiber surface;

[0019] Step S5: Curing the heat-treated prepreg at 60±2℃ for 36~48 hours to solidify the polyurea matrix while keeping the latent monomers from reacting;

[0020] Step S6: Cut and stack the cured prepreg, and hot press it at 80~85℃ and 5.0~8.0MPa pressure.

[0021] The specific operation of step S1 is as follows: First, the fiber fabric is subjected to plasma treatment for 45 to 60 seconds under an argon atmosphere and a power of 300 to 500W to generate a micro-rough structure and active free radicals; then, it is immersed in an interface modifier solution under an ultrasonic frequency of 40kHz and a power of 200 to 300W for reaction.

[0022] During the heat treatment in step S4, because the Lewis basicity of the pyridine group introduced by the interface modifier is significantly stronger than that of the urea nitrogen atom in the polyurea backbone, according to thermodynamic principles, boron atoms in the resin preferentially detach from the nitrogen atom in the backbone and migrate to the fiber surface to form more stable coordination bonds with the pyridine ring. This ligand substitution effect results in chemical bonding and anchoring between the resin matrix and the reinforcing fiber. Under ballistic impact, this strong interfacial bonding force based on coordination bonds can effectively resist shear slip between the fiber and the resin, forcing the projectile to shear the fiber rather than push it away, thus solving the window effect that easily occurs in traditional flexible bulletproof materials.

[0023] In addition, the curing and molding temperatures in steps S5 and S6 are both below 100°C, ensuring that the latent monomer bisphenol A cyanate does not react during material preparation and storage. It is only triggered after being subjected to a high-energy impact that causes the B←N bond to break and release the catalyst, thus ensuring the flexibility and comfort of the material when worn.

[0024] In summary, this application has the following beneficial effects:

[0025] 1. This invention introduces a dynamic B←N coordination bond formed by triarylborane and the nitrogen atom in the main chain into a polyurea matrix, and, in conjunction with a latent cyanate monomer, constitutes a mechanochemical response system. Under the high strain rate load of ballistic impact, the B←N coordination bond preferentially breaks to dissipate energy. This process dissociates the bound boron atom catalyst, which then initiates the in-situ polymerization reaction of the latent monomer. This impact-induced rapid transition from a flexible to a rigid state causes the material to produce a hardening effect at the impact site, thereby controlling the depth of the back indentation while maintaining flexibility under normal conditions and reducing the risk of blunt force trauma.

[0026] 2. This invention utilizes the Lewis acid-base affinity potential difference principle to construct a pyridine group interface on the surface of ultra-high molecular weight polyethylene fibers, where the Lewis base is stronger than that of the resin matrix. During the preparation process, this potential difference drives the boron centers in the resin to migrate directionally to the fiber surface, forming an interfacial chemical anchoring based on strong coordination bonds. This superior interfacial bonding force is far superior to traditional physical impregnation, firmly locking the fiber position and forcing it to shear rather than push away during bullet impact. This completely solves the fiber slippage and wave transmission problems that easily occur in flexible fabrics, significantly improving penetration resistance.

[0027] 3. This invention is entirely based on molecular-level design of organic polymers, eliminating the need for heavy solid fillers, which reduces the areal density of the bulletproof composite material by 20% to 30%, significantly reducing the load on individual soldiers. Simultaneously, this homogeneous polymer network structure completely eliminates the risks of particle sedimentation, agglomeration, and liquid leakage inherent in traditional STF fluids, endowing the material with excellent resistance to damp heat aging and ensuring the stability of the bulletproof performance during long-term storage and use. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for preparing a bulletproof material based on polymer composite materials, as provided in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0031] Ultra-high molecular weight polyethylene fiber fabric: plain weave, single filament fineness 1.5~2.5 dtex, areal density 130~160 g / m².

[0032] Liquefied diphenylmethane diisocyanate: Modified MDI, a light yellow transparent liquid at room temperature, with an -NCO content of 28.0%~30.0%.

[0033] Amino-terminated polyethers:

[0034] Specification 1: Model D-2000, bifunctional, weight-average molecular weight approximately 2000.

[0035] Specification 2: Model T-5000, trifunctional, weight-average molecular weight approximately 5000.

[0036] Triborane: Purity ≥ 98%, functionalized chain extender.

[0037] Bisphenol A cyanate: purity ≥99%, latent monomer, white crystalline powder, melting point 79~81℃.

[0038] 3-Aminopropyltriethoxysilane: analytical grade, with common coupling agents used for comparison.

[0039] Fumed silica: hydrophilic, specific surface area 200±25m² / g, native particle size approximately 12nm.

[0040] Anhydrous ethanol: analytical grade, purity ≥99.7%.

[0041] Argon: High-purity argon, purity ≥ 99.999%.

[0042] Example 1: This example provides a bulletproof material based on polymer composite materials and its preparation method. See Appendix. Figure 1 The specific steps are as follows:

[0043] Step 1: Fiber surface functionalization treatment

[0044] Ultra-high molecular weight polyethylene fiber fabric was placed in a plasma treatment instrument and treated for 50 seconds under an argon atmosphere and a power of 400W. Subsequently, an alcohol-water solution containing 3.0 wt% 3-thiopropyltrimethoxysilane was prepared, and the pH was adjusted to 5.0. The plasma-treated fabric was then immersed in this solution and reacted under ultrasonic conditions of 60℃ and 40kHz for 40 minutes. After removal, it was washed with ethanol and dried at 85℃ for 3 hours to obtain a modified fabric with a strong Lewis basic pyridine group.

[0045] Step 2: Preparation of resin components

[0046] Component A: MDI-100 and D-2000 type amino-terminated polyether were mixed at a molar ratio of -NCO / -NH2 of 3.5:1 and reacted at 82°C for 2.5 hours to obtain a -NCO-terminated prepolymer. The -NCO content was found to be 16.5%.

[0047] Component B: Add 4.0g of triborane to 76.0g of T-5000 type amino-terminated polyether and stir at room temperature and 1200rpm for 40 minutes to ensure complete boron-nitrogen coordination. Then add 20.0g of bisphenol A type cyanate powder, heat to 45℃ and stir for 1 hour to obtain a uniform slurry.

[0048] Step 3: Preparation of composite materials

[0049] Component A and component B were mixed in a static mixer at a ratio of 1.08 isocyanate index and then coated onto the surface of the modified fabric using a scraping method, with the resin content controlled at 20.0 wt%.

[0050] The prepreg is placed in a 105°C heating oven and left to stand for 6 minutes.

[0051] It was then placed in a constant temperature room at 60℃ for 48 hours to mature.

[0052] The 40 layers of cured prepreg are laid in 0° / 90° layers and hot-pressed in a flat vulcanizing machine at 80° and 6.0MPa pressure for 25 minutes. After cooling and demolding, the product is obtained.

[0053] Example 2: This example provides a bulletproof material based on polymer composite materials and its preparation method. The specific steps are as follows:

[0054] Step 1: Fiber surface functionalization treatment

[0055] Ultra-high molecular weight polyethylene fiber fabric was placed in a plasma treatment instrument and treated for 50 seconds under an argon atmosphere and a power of 400W. Subsequently, an alcohol-water solution containing 3.0 wt% 3-thiopropyltrimethoxysilane was prepared, and the pH was adjusted to 5.0. The plasma-treated fabric was then immersed in this solution and reacted under ultrasonic conditions of 60℃ and 40kHz for 40 minutes. After removal, it was washed with ethanol and dried at 85℃ for 3 hours to obtain a modified fabric with a strong Lewis basic pyridine group.

[0056] Step 2: Preparation of resin components

[0057] Component A: MDI-100 and D-2000 type amino-terminated polyether were mixed at a molar ratio of -NCO / -NH2 of 3.5:1 and reacted at 82°C for 2.5 hours to obtain a -NCO-terminated prepolymer. The -NCO content was found to be 16.5%.

[0058] Component B: Add 4.0g of triborane to 81.0g of T-5000 type amino-terminated polyether and stir at room temperature and 1200rpm for 40 minutes to ensure complete boron-nitrogen coordination. Then add 15.0g of bisphenol A type cyanate powder, heat to 45℃ and stir to disperse for 1 hour to obtain a uniform slurry.

[0059] Step 3: Preparation of composite materials

[0060] Component A and component B were mixed in a static mixer at a ratio of 1.08 isocyanate index and then coated onto the surface of the modified fabric using a scraping method, with the resin content controlled at 20.0 wt%.

[0061] The prepreg is placed in a 105°C heating oven and left to stand for 6 minutes.

[0062] It was then placed in a constant temperature room at 60℃ for 48 hours to mature.

[0063] The 40 layers of cured prepreg are laid in 0° / 90° layers and hot-pressed in a flat vulcanizing machine at 80° and 6.0MPa pressure for 25 minutes. After cooling and demolding, the product is obtained.

[0064] Example 3: This example provides a bulletproof material based on polymer composite materials and its preparation method. The specific steps are as follows:

[0065] Step 1: Fiber surface functionalization treatment

[0066] Ultra-high molecular weight polyethylene fiber fabric was placed in a plasma treatment instrument and treated for 50 seconds under an argon atmosphere and a power of 400W. Subsequently, an alcohol-water solution containing 3.0 wt% 3-thiopropyltrimethoxysilane was prepared, and the pH was adjusted to 5.0. The plasma-treated fabric was then immersed in this solution and reacted under ultrasonic conditions of 60℃ and 40kHz for 40 minutes. After removal, it was washed with ethanol and dried at 85℃ for 3 hours to obtain a modified fabric with a strong Lewis basic pyridine group.

[0067] Step 2: Preparation of resin components

[0068] Component A: MDI-100 and D-2000 type amino-terminated polyether were mixed at a molar ratio of -NCO / -NH2 of 3.5:1 and reacted at 82°C for 2.5 hours to obtain a -NCO-terminated prepolymer. The -NCO content was found to be 16.5%.

[0069] Component B: Add 4.0g of triborane to 76.0g of T-5000 type amino-terminated polyether and stir at room temperature and 1200rpm for 40 minutes to ensure complete boron-nitrogen coordination. Then add 20.0g of bisphenol A type cyanate powder, heat to 45℃ and stir for 1 hour to obtain a uniform slurry.

[0070] Step 3: Preparation of composite materials

[0071] Component A and component B were mixed in a static mixer at a ratio of 1.08 isocyanate index and then coated onto the surface of the modified fabric using a scraping method, with the resin content controlled at 20.0 wt%.

[0072] The prepreg is placed in a 95°C heating oven and left to stand for 8 minutes.

[0073] It was then placed in a constant temperature room at 60℃ for 48 hours to mature.

[0074] The 40 layers of cured prepreg are laid in 0° / 90° layers and hot-pressed in a flat vulcanizing machine at 80° and 6.0MPa pressure for 25 minutes. After cooling and demolding, the product is obtained.

[0075] Comparative Example 1: Compared with Example 1, the difference is that the latent monomer bisphenol A cyanate was not added to component B, and component B consists only of terminal amino polyether and functionalized chain extender triborane. The other raw materials and preparation process are the same.

[0076] Comparative Example 2: Compared with Example 1, the difference is that the interface modifier 3-thiopropyltrimethoxysilane in step 1 was replaced with ordinary 3-aminopropyltriethoxysilane, while the other raw materials and preparation process were the same.

[0077] Comparative Example 3: Compared with Example 1, the difference is that the resin system does not contain triborane and bisphenol A cyanate. Instead, a common polyurea matrix is ​​prepared by using conventional amine chain extenders, terminal amino polyethers, and MDI. 20.0 wt% of fumed silica nanoparticles are physically blended into the resin. The 105°C thermally induced ligand replacement treatment in step 3 is not performed during the preparation process. All other aspects are the same.

[0078] Test Example 1: Ballistic Impact Resistance Test. This test example aims to evaluate the ballistic impact resistance of the ballistic composite material plates prepared in the above embodiments and comparative examples.

[0079] The specific experimental steps are as follows:

[0080] The composite board sample to be tested was cut into 400mm×400mm sizes and placed in a constant temperature and humidity environment of 20±2℃ and 65±5% for more than 24 hours to eliminate the interference of ambient temperature and humidity on the performance of the polymer matrix.

[0081] The pretreated sample is fixed in front of the standard backing material, and nylon straps are used to firmly adhere the sample to the surface of the backing putty, ensuring no gaps. The backing putty needs to be pre-calibrated by drop ball rebound to ensure that the rebound depth is within the standard range.

[0082] A universal firearm receiver equipped with a laser sight was used, and the barrel length was the standard length compatible with the test ammunition. The test ammunition used was a 9mm full metal jacketed round-nosed bullet with a bullet weight of 8.0g.

[0083] Two sets of infrared light curtain velocity measurement systems are installed between the muzzle and the target plate to accurately measure the instantaneous velocity of the projectile before it hits the target plate.

[0084] Multiple shots of the same sample at different velocities were fired, and the propellant charge was adjusted to change the projectile velocity. The highest velocity that resulted in partial penetration and the lowest velocity that resulted in complete penetration were recorded. The arithmetic mean of at least six mixed results was taken as the V50 value of the sample.

[0085] The projectile's incident velocity was controlled at 430±10m / s. The sample was fired vertically. After firing, the composite plate was removed, and the maximum indentation depth on the backing putty was measured using a digital depth gauge. At least three effective impact points were measured for each sample, and the average value was taken.

[0086] Before testing, the sample mass was weighed using a precision electronic balance, and its mass per unit area was calculated.

[0087] The test results are shown in Table 1 below:

[0088] Group Surface density (kg / m²) V50 ballistic maximum velocity (m / s) BFS back indentation depth (mm) Example 1 5.82 568.4 24.3 Example 2 5.76 552.1 27.9 Example 3 5.81 561.7 25.4 Comparative Example 1 5.64 513.5 38.6 Comparative Example 2 5.83 497.2 32.4 Comparative Example 3 7.51 526.8 30.7

[0089] Comparing the data of Example 1 and Comparative Example 1 reveals that, in the absence of the latent monomer bisphenol A cyanate, although Comparative Example 1 still possesses a boron-containing polyurea matrix, its back indentation depth reaches 38.6 mm, significantly inferior to the 24.3 mm of Example 1. This result confirms the effectiveness of the mechanochemical catalytic curing mechanism described in this invention. In Example 1, when the high energy of the ballistic impact forces the B←N coordination bonds in the polymer network to break to dissipate energy, the Lewis acid catalyst, which was originally in a caged state, is released, thereby catalyzing the latent monomer dispersed in the matrix to undergo a rapid chemical crosslinking reaction. This instantaneous chemical hardening effect triggered by physical impact leads to a sharp increase in the matrix modulus of the impacted area, thereby greatly limiting the deformation of the composite material in the thickness direction and effectively controlling the risk of blunt force trauma.

[0090] Comparative data from Example 1 and Comparative Example 2 show that the V50 value of the material decreases significantly when the interface modifier lacks strong Lewis basicity. This indicates that the thermodynamically driven anchoring mechanism based on Lewis acid-base affinity is crucial for improving ballistic penetration resistance. During the preparation process of Example 1, the boron centers in the resin undergo directional migration induced by the strongly basic pyridine groups at the interface, achieving chemical bonding and anchoring between the resin and the ultra-high molecular weight polyethylene fiber. This strong interfacial bonding effectively inhibits the lateral shear slip of the fiber under high strain rate impact, forcing the projectile to shear through the high-strength fiber to penetrate, thereby significantly improving the system's energy absorption efficiency and avoiding window effect failure caused by fiber slippage.

[0091] Furthermore, comparing the data from Example 1 and Comparative Example 3, it is evident that the composite material prepared by this invention, with an areal density of only 5.82 kg / m², exhibits significantly superior ballistic performance compared to traditional physically doped materials with an areal density as high as 7.51 kg / m². While Comparative Example 3, employing physical filling with inorganic nanoparticles, can improve performance to some extent through shear thickening, the high-density filler significantly increases the material's weight. In contrast, this invention completely eliminates inorganic particle fillers, relying solely on the molecular structure design and interface control of the polymer matrix to achieve high-performance protection at low areal density, demonstrating the significant technical advantages of this dynamic response network in the field of lightweight protection.

[0092] Example 2: Interlaminar Shear Strength Test. This example aims to quantitatively evaluate the interfacial bonding quality between the modified resin matrix and ultra-high molecular weight polyethylene fibers. Since interlaminar delamination and fiber slippage are among the main failure modes of ballistic composite materials under ballistic impact, interlaminar shear strength is a key mechanical indicator reflecting the interfacial anchoring effect.

[0093] The specific experimental steps are as follows:

[0094] Long strip-shaped samples were cut from the central region of the composite boards prepared in Examples 1-3 and Comparative Examples 1-3 using a water jet cutting machine. The sample dimensions were set as follows: length 20 mm, width 6.0 mm, and thickness determined according to the actual pressing thickness. To eliminate the influence of stress concentration at the cutting edge, the sides of the samples were lightly sanded and polished using 400-grit sandpaper.

[0095] A universal testing machine equipped with a 5kN force sensor was used, and a three-point bending fixture specifically designed for short beam shearing was installed.

[0096] The ratio of the lower support span to the specimen thickness was set at 4:1 to ensure that the specimen mainly experiences interlaminar shear failure rather than tensile or compressive failure during bending. The indenter diameter was 6.0 mm, and the support cylinder diameter was 3.0 mm.

[0097] Place the specimen horizontally at the center of the two lower supports, and adjust the upper indenter to make it rigidly contact the upper surface of the specimen. Apply a load vertically downward at a constant loading rate of 1.0 mm / min until the load reaches its peak and then decreases by 30% or the specimen shows obvious delamination fracture, at which point the test is stopped.

[0098] The system automatically records the load-displacement curve and the maximum failure load Pmax. The interlaminar shear strength is calculated according to the formula ILSS=0.75×Pmax / (b×h), where b is the specimen width and h is the specimen thickness. Five parallel specimens are tested for each group of samples, and the arithmetic mean is taken after removing discrete values.

[0099] The test results are shown in Table 2 below:

[0100] Group Average thickness (mm) Maximum breaking load (N) Interlaminar shear strength (ILSS) (MPa) Example 1 2.84 968.3 42.63 Example 2 2.81 941.5 41.87 Example 3 2.83 849.2 37.52 Comparative Example 1 2.79 903.6 40.48 Comparative Example 2 2.85 509.4 22.34 Comparative Example 3 2.91 596.1 25.61

[0101] The data comparison between Example 1 and Comparative Example 2 intuitively reveals the decisive influence of Lewis acid-base affinity difference on interfacial bonding performance. Example 1 exhibits an interlaminar shear strength as high as 42.63 MPa, while Comparative Example 2, where the interfacial modifier was replaced with a common aminosilane, only reaches 22.34 MPa, a performance difference of nearly 100%. This is because in Comparative Example 2, the amine groups on the fiber surface and the urea / amine groups in the resin matrix have similar Lewis basicity strengths, lacking thermodynamic driving forces. This results in the boron-containing chain extender being randomly distributed in the matrix and failing to accumulate at the interface. Conversely, Example 1 utilizes the significantly stronger Lewis basicity of the pyridine group compared to the nitrogen atom of the urea group to construct a clear affinity hierarchy. During thermal induction, electron-deficient boron centers in the resin actively migrate from the resin backbone to the fiber surface and undergo ligand substitution reactions to seek a more stable coordination environment, thereby forming a high-density chemical bonding anchor points at the two-phase interface, greatly enhancing the ability to resist interlaminar shear slip.

[0102] The effect of process parameters on the activation of the interface anchoring mechanism was verified by comparing Examples 1 and 3. Although Example 3 used the same raw material system, its ILSS value was significantly lower than that of Example 1 because the thermal induction treatment temperature was reduced to 95°C. This phenomenon indicates that the ligand substitution reaction is a thermodynamically controlled process and is limited by the mobility of polymer chain segments. Higher treatment temperatures can endow polymer chain segments with greater free volume and kinetic energy, reduce the activation energy barrier for boron center migration and substitution reactions, and promote more boron atoms to jump to strong base sites on the fiber surface. Therefore, a specific heat treatment process window is a necessary condition for realizing the interface-targeted anchoring mechanism described in this invention, ensuring the maximization of chemical bond density.

[0103] Furthermore, the data from Comparative Example 3 further corroborates the superiority of chemical coordination anchoring over traditional physical interactions. Comparative Example 3 employed a traditional MOCA chain extender system and physically blended fillers. The bond between the resin and ultra-high molecular weight polyethylene fibers relied primarily on van der Waals forces and weak physical-mechanical interlocking, resulting in weak adhesion and a high susceptibility to debonding under shear stress. In contrast, both Example 1 and Comparative Example 1 introduced boron-containing coordination systems. Even without latent monomers, Comparative Example 1 maintained a high ILSS value, indicating that the interfacial reinforcement was primarily attributed to the formation of boron-nitrogen coordination bonds. This strong interfacial interaction based on coordination bonds ensures that the composite material can effectively transfer stress from the matrix to the high-modulus fibers under the high shear stress environment of ballistic impact, avoiding a decrease in energy absorption efficiency due to premature interfacial failure.

[0104] Experiment 3: Dynamic Impact Compression Test. This experiment uses a split Hopkinson bar apparatus to characterize the dynamic mechanical response of the composite material under high strain rate conditions simulating ballistic impact, verifying whether a force-chemical hardening effect triggered by the impact load occurs within the material.

[0105] The specific experimental steps are as follows:

[0106] To meet the SHPB test requirement for uniform stress wave propagation, cylindrical specimens need to be prepared. The laminates prepared in each embodiment and comparative example are stacked and bonded along the thickness direction, and then machined into cylindrical specimens with a diameter of 10.0 mm and a height of 8.0 mm using a diamond core drill bit. After machining, the end faces of the specimens are ground to ensure that the parallelism deviation between the two end faces is less than 0.02 mm and that the end faces are perpendicular to the axis.

[0107] The experimental setup consists of a high-pressure gas cannon, an impact rod, an incident rod, a transmission rod, and a buffer energy absorption device. All rods are made of high-strength maraging steel and have a diameter of 14.5 mm. Semiconductor resistance strain gauges are attached to the middle of the incident and transmission rods and connected to an ultra-dynamic strain gauge and a transient waveform memory.

[0108] Apply molybdenum disulfide grease evenly to both ends of the sample to eliminate the interference of end-face friction on the experimental results. Clamp the sample coaxially between the incident rod and the transmission rod.

[0109] The air pressure in the air gun pressure chamber is adjusted to drive the impact rod to strike the incident rod at a specific speed, generating an elastic compression wave. By adjusting the air pressure, the average engineering strain rate of the sample is controlled to be stable within the range of 3000±100 s−1.

[0110] The system synchronously records the voltage signals of the incident wave, reflected wave, and transmitted wave. Based on the one-dimensional elastic wave theory and the three-wave method, the dynamic true stress-strain curve of the sample during the impact process is calculated. The maximum rheological stress on the curve is selected as the dynamic peak stress.

[0111] In comparison, a compression test was performed on a specimen of the same specification using an electronic universal testing machine at a low strain rate of 0.001 s−1 to determine its yield stress.

[0112] The test results are shown in Table 3 below:

[0113] Group Measured average strain rate (s−1) Quasi-static yield stress (MPa) Dynamic peak stress (MPa) Dynamic hardening factor (Ratio) Example 1 2985 42.4 362.1 8.54 Example 2 3012 41.9 286.5 6.84 Example 3 3005 42.1 351.2 8.34 Comparative Example 1 2994 43.5 104.8 2.41 Comparative Example 2 3021 42.6 346.3 8.13 Comparative Example 3 2978 48.2 203.4 4.22

[0114] The data differences between Example 1 and Comparative Example 1 reveal the existence of the core "mechanical-chemical" response mechanism of this invention. Under quasi-static conditions, the yield stresses of the two groups of samples are similar, indicating that under conventional low-speed loading, the latent monomers do not react, and the material exhibits typical flexible polyurea characteristics. However, under a high strain rate impact of 3000 s−1, the dynamic peak stress of Example 1 surges to 362.1 MPa, with a dynamic hardening factor as high as 8.54; while Comparative Example 1, lacking the latent monomer bisphenol A cyanate, has a dynamic hardening factor of only 2.41. This significant difference confirms that Example 1 underwent a qualitative change in its microstructure at the moment of impact. When the high-energy shock wave passes through the matrix, the boron-nitrogen coordination bonds are forcibly dissociated, and the released active boron centers catalyze the surrounding cyanate monomers in a very short time, generating a highly rigid triazine ring network. This chemical curing reaction, triggered in situ by the impact energy, enables the material to achieve an instantaneous transformation from a rubber state to a ceramic state, thereby providing extremely high compressive strength to resist projectile penetration.

[0115] The regulatory effect of latent monomer concentration on the dynamic hardening effect was demonstrated in the comparison between Example 1 and Example 2. In Example 2, the content of latent monomer was reduced by 5 percentage points compared to Example 1, resulting in a decrease in the dynamic peak stress to 286.5 MPa and a corresponding decrease in the dynamic hardening factor to 6.84. This data trend indicates that the degree of chemical reaction within the system is positively correlated with the concentration of reactants. A higher monomer concentration means that a more rigid network with higher crosslinking density can be formed after catalyst release, thereby producing a stronger hardening effect. This further corroborates that the protection mechanism of the present invention does not rely solely on physical filling or viscoelastic damping, but rather on a controllable chemical reaction kinetic process.

[0116] For Example 1 and Comparative Example 2, which use different interface modifiers, although both exhibited high dynamic hardening factors, indicating that chemical curing occurred within their matrices, the high hardening factor of Comparative Example 2, combined with the interlaminar shear data from Test Example 2, did not translate into excellent ballistic resistance. This is because the SHPB compression test primarily reflects the compressive strength of the material matrix, while actual ballistic protection also involves interlaminar synergistic energy dissipation. Example 1, while maintaining high dynamic hardening of the matrix, combined with excellent interface anchoring, achieved a synergistic effect between matrix hardening and fiber tensile strength. Although Comparative Example 3 introduced inorganic fillers to generate physical shear thickening, its hardening amplitude was far lower than that of the chemically cured system of this invention, and it was accompanied by an increase in density, demonstrating the technical advantages of this invention in terms of specific strength and dynamic response efficiency.

[0117] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A bulletproof material based on polymer composite materials, characterized in that, The bulletproof material is composed of a modified ultra-high molecular weight polyethylene fiber fabric and a mechanochemically responsive polyurea matrix impregnated between its layers; The mechanochemically responsive polyurea matrix is ​​a product formed by the reaction and curing of component A and component B with an isocyanate index of 1.05 to 1.10, and unreacted latent monomers are dispersed in the matrix; Component A comprises a prepolymer formed by the reaction of diphenylmethane diisocyanate and amino-terminated polyether; Component B comprises an amino-terminated polyether, triborane as a functionalized chain extender serving as a Lewis acid source, and bisphenol A cyanate as a latent monomer. The modified ultra-high molecular weight polyethylene fiber fabric has a hydrolytic condensate derived from the interface modifier 3-thiopropyltrimethoxysilane grafted onto its surface. The Lewis basicity of the pyridine group provided by the interface modifier is stronger than that of the urea nitrogen atom in the polyurea matrix.

2. The bulletproof material based on polymer composite materials according to claim 1, characterized in that, The modified ultra-high molecular weight polyethylene fiber fabric is obtained by the following method: The ultra-high molecular weight polyethylene fiber fabric is first subjected to plasma etching treatment, then immersed in an alcohol-water solution of the interface modifier with a mass concentration of 2.0%~4.0%, and subjected to an ultrasonic-assisted grafting reaction at 50~65°C, and then dried to obtain the final product.

3. The bulletproof material based on polymer composite materials according to claim 1, characterized in that, The composition of component B, by mass percentage, is as follows: Amino-terminated polyethers: 69.0%~82.0%; Functionalized chain extender triborane: 3.0%~6.0%; Latent monomer bisphenol A cyanate: 15.0%~25.0%.

4. The bulletproof material based on polymer composite materials according to claim 1, characterized in that, The mass fraction of the mechanochemically responsive polyurea matrix in the bulletproof material is 18.0%~22.0%; the bulletproof material is composed of 30~50 layers of the modified ultra-high molecular weight polyethylene fiber fabric laminated together.

5. A method for preparing a bulletproof material based on polymer composite materials, characterized in that, A bulletproof material based on a polymer composite material as described in any one of claims 1-4, comprising the following steps: S1: Surface treatment of ultra-high molecular weight polyethylene fiber fabric with grafting of interface modifier 3-thiopropyltrimethoxysilane to obtain modified fiber fabric. S2: Prepare component A and component B, wherein component A is an isocyanate prepolymer, and component B is prepared by premixing functionalized chain extender triborane with amino-terminated polyether to form a coordination structure, and then adding latent monomer bisphenol A type cyanate for dispersion. S3: Mix component A and component B and coat the mixture onto the surface of the modified fiber fabric to obtain a prepreg. S4: Heat-treat the prepreg at 95~110℃ for 5~8 minutes to induce the boron centers in the resin to migrate and coordinate to the pyridine groups on the fiber surface; S5: The heat-treated prepreg is cured at 60±2℃ for 36~48 hours to cure the polyurea matrix and prevent the latent monomers from reacting; S6: Cut and stack the cured prepreg, and hot press it at 80~85℃ and 5.0~8.0MPa pressure.

6. The method for preparing a bulletproof material based on polymer composite materials according to claim 5, characterized in that, The surface treatment in step S1 specifically includes: First, the fiber fabric is plasma-treated for 45-60 seconds in an argon atmosphere at a power of 300-500W, and then immersed in an interface modifier solution for reaction under ultrasonic conditions at a frequency of 40kHz and a power of 200-300W.

7. The method for preparing a bulletproof material based on a polymer composite material according to claim 5, characterized in that, The preparation conditions for component A in step S2 are as follows: Diphenylmethane diisocyanate and amino-terminated polyether with a molecular weight of 2000 are mixed at a molar ratio of NCO to NH2 of 3.0:1 to 4.0:1 and reacted at 80 to 85°C for 2.0 to 2.5 hours, with the NCO content controlled at 15% to 18%.

8. The method for preparing a bulletproof material based on a polymer composite material according to claim 5, characterized in that, The preparation process of component B in step S2 includes: First, triborane is added to an amino-terminated polyether with a molecular weight of 5000 and stirred at high speed for 30-45 minutes at room temperature to complete the catalyst cage. Then, powdered bisphenol A cyanate is added and stirred and dispersed at 40-50°C for 1.0-1.5 hours.

9. A method for preparing a bulletproof material based on a polymer composite material according to claim 5, characterized in that, The temperature setting for the heat treatment in step S4 is based on: This temperature is higher than the polyurea chain segment movement temperature and lower than the thermal polymerization initiation temperature of the latent monomer. The Lewis basicity difference between the pyridine groups on the fiber surface and the urea nitrogen atoms in the matrix is ​​used to drive the ligand substitution reaction.

10. A method for preparing a bulletproof material based on a polymer composite material according to claim 5, characterized in that, The hot pressing temperature in step S6 is strictly controlled below 100°C to ensure that the bisphenol A cyanate in the final bulletproof material remains in an unpolymerized latent state.

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