Water-based adhesive for bulletproof UD cloth, preparation method and application thereof

Abstract

The application discloses a water-based adhesive for bulletproof UD cloth and a preparation method and application thereof, and belongs to the technical field of water-based adhesives. The preparation method comprises the following steps: preparing a polycarbonate-based prepolymer by reacting polycarbonate diol with diisocyanate; performing chain extension and hydrophilic modification on the prepolymer by adding polypropylene glycol and diisocyanate; adding an acrylate monomer to perform free radical copolymerization and external crosslinking after neutralization and dispersion, so as to obtain the water-based adhesive. The adhesive utilizes the surface migration and enrichment of the polycarbonate segment in the film forming process to form a gradient structure with a decreasing carbonate content from the surface to the inside, and simultaneously realizes low surface energy and high elasticity, and can reduce the back convex deformation when used for the bulletproof UD cloth.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, and particularly relates to a water-based adhesive for bulletproof UD fabric, its preparation method and application. Background Technology

[0002] Bulletproof UD fabric, also known as unidirectional non-woven fabric, is a composite material made by impregnating high-strength fibers with an adhesive and arranging them in a unidirectional parallel orientation. It is widely used in personal protective equipment such as soft bulletproof vests and bulletproof helmets. In recent years, adhesive technology in this field has continued to develop towards water-based methods. CN117264572A (publication date December 22, 2023, applicant Shandong Northern Modern Chemical Industry Co., Ltd.) discloses a water-based adhesive for pressure-sensitive UD fabric, which uses hydroxymethylacrylamide and carbomer resin to construct an acrylate crosslinking system. The amino groups in hydroxymethylacrylamide and the carboxylic acid groups in carbomer resin are crosslinked to form a tight interface, which is used to bond ultra-high molecular weight polyethylene fibers to prepare bulletproof vests. CN106675494A (publication date May 17, 2017, applicant Yu Mingliang) discloses a water-based polyurethane adhesive for bulletproof composite materials, which uses polymer polyol and modified polyisocyanate as the matrix, and improves the tensile properties and thermal conductivity of the adhesive by modifying the polyisocyanate with graphene oxide. The aforementioned existing technologies represent the two main technical routes for current water-based adhesives for bulletproof UD fabric—acrylate systems and polyether-type polyurethane systems—but neither involves the application of polycarbonate segments in the adhesive.

[0003] Specifically, while acrylate systems offer good film-forming properties and low cost, their elasticity is insufficient, resulting in significant back-convex deformation of bulletproof UD fabric upon impact. Ordinary polyether-based polyurethane systems, while exhibiting superior flexibility, suffer from high surface energy (typically >40 mN / m) and poor interlayer slip energy dissipation. Neither system utilizes the surface self-migration characteristics of polycarbonate segments during film formation—that is, the spontaneous accumulation of polycarbonate segments on the film surface due to differences in polarity and between hard and soft segments, forming a unique carbonate content gradient structure under the synergistic effect of thermodynamic compatibility differences and interfacial activity. This invention, based on the understanding of this mechanism, overcomes the bias of existing technologies that rely solely on the intrinsic properties of raw materials.

[0004] The ballistic performance of bulletproof UD fabric depends not only on the strength and modulus of the reinforcing fibers, but also to a large extent on the mechanical properties of the adhesive itself. Yang SH, Zhai SM, Piao MX, Wang X, Shi HF, Li CL. Analysis of Water-Based Polyurethane Properties in the Ballistic Behavior of Ultra-High Molecular Weight Polyethylene Fiber Composites, Polymers, 2025, 17(7):837, DOI:10.3390 / polym17070837 (https: / / doi.org / 10.3390 / polym17070837) systematically studied the influence of the hard segment content and modulus of waterborne polyurethane adhesive on the ballistic behavior of ultra-high molecular weight polyethylene fiber composites. The results showed that when the hard segment content increased from 45% to 65%, the rigidity of the adhesive increased significantly, the V50 value decreased sharply from 541 m / s to 465 m / s, and the delamination area decreased from 50.79 cm². 2 Increased to 104.13cm 2 When the hard segment content decreased from 45% to 35%, the adhesive became too soft, resulting in insufficient interlaminar shear strength and a V50 value of 514 m / s. This study reveals that an overly stiff adhesive restricts fiber-coordinated deformation, leading to severe delamination failure, while an overly soft adhesive results in insufficient interlaminar load transfer. Only when the optimal balance between stiffness and toughness is achieved—that is, when the hard segment content is approximately 45%—can the highest energy absorption efficiency and minimal damage be realized.

[0005] However, most widely used waterborne polyurethane-acrylate adhesives currently employ polyether-type polyols such as polypropylene glycol and polytetrahydrofuran ether glycol as soft segments to construct polyurethane prepolymers. While polyether segments can provide a certain degree of flexibility to maintain the rigidity-toughness balance of the adhesive, their molecular structure lacks specific functional groups capable of reducing surface energy, resulting in adhesive films with surface energy typically exceeding 40 mN / m. This high surface energy leads to excessively strong interlayer adhesion in UD fabric layups, restricting interlayer slippage during impact. Impact energy cannot be effectively dissipated through this crucial mechanism, ultimately resulting in a lower V50 ballistic limit and a larger back-convex deformation depth. Furthermore, polyether-type polyurethanes exhibit insufficient resistance to humid heat aging, leading to significant performance degradation of the adhesive film under high-temperature and high-humidity service environments, further restricting the long-term reliability of ballistic UD fabrics. Therefore, achieving both low surface energy and high elasticity in a waterborne polyurethane-acrylate system has become a long-standing technical bottleneck in improving the ballistic performance of ballistic UD fabrics. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a water-based adhesive for bulletproof UD fabric, its preparation method and application. By introducing polycarbonate-based prepolymers into a water-based polyurethane-acrylate system, the carbonate segments spontaneously migrate and accumulate to the surface of the adhesive film during the film formation process to form a gradient structure in which the carbonate content decreases from the surface to the interior. This allows the adhesive film to simultaneously obtain low surface energy and high elasticity. When used in bulletproof UD fabric, it imparts a wrapping layer effect to the layup, which moderately slips and dissipates energy under impact without disintegrating, and the retention rate of resistance to damp heat aging is slightly improved.

[0007] The "similar to a wrapping layer effect" refers to the fact that the adhesive film allows moderate interlayer slippage between the UD fabric layers under impact to dissipate impact energy, while maintaining structural integrity by relying on the high elasticity of the adhesive film itself, preventing the layers from disintegrating. Its macroscopic function is similar to the wrapping layer's restraining effect on the ceramic panel in a traditional rigid bulletproof structure, but the mechanism is different—traditional wrapping layers rely on the high strength of the outer material for passive restraint, while this invention achieves active slippage energy dissipation through the synergy of the adhesive film's low surface energy and high elasticity.

[0008] The first aspect of this invention discloses a method for preparing a water-based adhesive for bulletproof UD fabric, comprising the following components by weight: 5-12 parts of polycarbonate-based prepolymer, 30-40 parts of polypropylene glycol with a number average molecular weight of 2000 14-18 parts of diisocyanate, 22-28 parts of butyl acrylate, 1-2 parts of hydroxyethyl acrylate Dimethylolpropionic acid 2.5~3.5 parts, Neutralizing agent 1.0~1.5 parts, Aziridine crosslinking agent 0.3~0.4 parts, 0.1-0.2 parts of polyether-modified siloxane defoamer. 193-219 parts of deionized water; The functions of each component in the system are as follows: Polycarbonate-based prepolymers: provide polycarbonate segments that spontaneously migrate to the film surface during film formation through the synergistic effect of thermodynamic compatibility differences and interfacial activity, forming a gradient structure and achieving a synergy of low surface energy and high elasticity. Polypropylene glycol: As the soft segment matrix, it provides basic flexibility and elastic recovery capability; Diisocyanate: reacts with polyols to form the polyurethane backbone, providing hard segments to maintain the cohesive strength of the film; Butyl acrylate and hydroxyethyl acrylate: as comonomers, they undergo free radical copolymerization with polyurethane prepolymer to form a polyurethane-acrylate interpenetrating / grafted network, which balances the flexibility and adhesion of the film. Dimethylolpropionic acid: Introduces a hydrophilic carboxyl group to achieve water dispersibility of the system, enabling the adhesive to be stably dispersed in an aqueous system; Neutralizing agent: neutralizes the carboxyl groups in dimethylolpropionic acid, promoting the water dispersion process; Aziridine crosslinking agent: It undergoes an external crosslinking reaction with carboxyl groups at room temperature, thereby improving the cohesive strength and aging resistance of the film; Polyether-modified siloxane defoamer: eliminates bubbles generated during dispersion and copolymerization, ensuring the uniformity and surface quality of the film.

[0009] The polycarbonate-based prepolymer is prepared by reacting polycarbonate diol with diisocyanate in a molar ratio of 1:2, and has an NCO content of 5.8~6.3 wt%. The polycarbonate diol is selected from at least one of polyhexanediol, polybutylene dicarbonate, and polypentylene dicarbonate, and has a number average molecular weight of 1000. The diisocyanate is selected from at least one of isophorone diisocyanate, hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate; The neutralizing agent is triethylamine and / or N-methylmorpholine; The preparation includes the following steps: Step 1: Dehydrate polycarbonate diol under vacuum at 110℃ and -0.08~-0.095MPa for 1.5 hours, cool down to 80℃, add diisocyanate at a molar ratio of 1:2, react at 80℃ for 3 hours under nitrogen protection, use di-n-butylamine titration to detect NCO content in real time, control the NCO content of the product to be 5.8~6.3wt%, cool down to 40℃ and discharge to obtain polycarbonate-based prepolymer for later use; Step 2: Dehydrate polypropylene glycol under vacuum at 110°C and a vacuum degree of -0.08 to -0.095 MPa for 1.5 hours, cool it down to 80°C, add diisocyanate and the polycarbonate-based prepolymer obtained in Step 1, and stir to react for 2 hours; then add dimethylolpropionic acid and acetone accounting for 5-10 wt% of the total mass of polycarbonate-based prepolymer, polypropylene glycol, and diisocyanate, and continue to react for 1.5 hours to reduce viscosity; Step 3: Cool down to 45℃, add neutralizing agent, stir and neutralize for 15 minutes; disperse at 1500rpm high speed shear for 10~20min, add deionized water for dispersion, and add polyether modified siloxane defoamer during dispersion. Step 4: Add butyl acrylate and hydroxyethyl acrylate, and add 0.3~0.8 wt% of ammonium persulfate initiator, which is a 5~10 wt% aqueous solution. The initiator is not included in the aforementioned weight components. Carry out a free radical copolymerization reaction at 65°C until the viscosity of the system stabilizes (viscosity fluctuation at 65°C does not exceed ±5% / 30min), and the reaction endpoint is indicated by visually observing no monomer droplets flowing back into the condenser. After the reaction, cool to room temperature, add aziridine crosslinking agent, and adjust the pH value to 7.1~7.3. Remove acetone under reduced pressure, with a vacuum degree of -0.08~-0.095MPa, a temperature of 40~50°C, and a removal time of 1~2h. Obtain the water-based adhesive for the bulletproof UD fabric.

[0010] The second aspect of this invention discloses a water-based adhesive for bulletproof UD fabric, which is prepared by the method described in the first aspect.

[0011] The aforementioned bulletproof UD fabric uses a water-based adhesive. The adhesive film has a gradient structure in which the carbonate content decreases from the surface to the interior. This was confirmed by variable-angle X-ray photoelectron spectroscopy (XPS) depth analysis. After C1s peak fitting to distinguish between carbonate carbonyl and urethane carbonyl groups, the area ratio of carbonate characteristic sub-peaks on the film surface is greater than that of carbonate characteristic sub-peaks in the film itself. Furthermore, the area ratio of carbonate characteristic sub-peaks decreases as the angle increases from 15° to 75°.

[0012] The third aspect of the present invention discloses a bulletproof UD fabric, comprising reinforcing fibers and a water-based adhesive for bulletproof UD fabric as described in the second aspect above; the bulletproof UD fabric is formed by the reinforcing fibers being impregnated with the adhesive and then arranged in a unidirectional parallel pattern.

[0013] The aforementioned bulletproof UD fabric uses ultra-high molecular weight polyethylene fiber as its reinforcing fiber.

[0014] The aforementioned bulletproof UD fabric is made by hot-pressing eight layers of the bulletproof UD fabric in a 0° / 90° orthogonal layup, under conditions of 90°×15min×3MPa.

[0015] The fourth aspect of the present invention discloses a bulletproof article comprising the bulletproof UD fabric described in the third aspect.

[0016] Compared with the prior art, the present invention has the following advantages: This invention introduces polycarbonate-based prepolymers into an aqueous polyurethane-acrylate adhesive system. Utilizing the spontaneous migration and enrichment of polycarbonate segments towards the film surface during film formation, a gradient structure with decreasing carbonate content from the surface to the interior is formed within the film. The mechanism lies in the following: the polarity of the polycarbonate segments lies between that of polyether soft segments and isocyanate hard segments. On one hand, there is a difference in thermodynamic compatibility with the PPG soft segment matrix, driving them to migrate towards the interface during film-forming phase separation. On the other hand, the isocyanate aliphatic / cycloaliphatic structures connected to both ends of the polycarbonate segments endow them with certain interfacial activity. Under the synergistic effect of these two factors, the carbonate segments spontaneously enrich towards the film surface, forming a thermodynamically stable gradient structure with a high surface carbonate group content and a bulk rich in compliant segments. In-depth X-ray photoelectron spectroscopy (XPS) analysis confirmed that in the C1s high-resolution spectrum, the OC=O characteristic peak near 289.0 eV was deconvolved into two sub-peaks: urethane carbonyl (~288.8 eV) and carbonate carbonyl (~289.4 eV). At a 15° angle, the carbonate sub-peak area on the film surface accounted for 11.5 at%, and the surface-to-bulk carbonate concentration ratio was 1.51, confirming the directional enrichment of carbonate groups on the surface. This gradient structure reduced the film surface energy to 30.2 mN / m, thus endowing the film with intrinsically low surface energy characteristics. Simultaneously, the flexibility of the polycarbonate segments resulted in an elongation at break of 680% and a Shore A hardness of 32, achieving a synergistic balance between low surface energy and high elasticity. This effectively solved the technical challenge of balancing high surface energy and flexibility in polyether-type waterborne polyurethane-acrylate adhesives.

[0017] The technical solution of this invention achieves a comprehensive improvement in technical effect through the following causal chain: 1. Polycarbonate-based prepolymer forms a gradient structure during film formation → the surface energy of the film is reduced → the interlayer adhesion strength of UD fabric is moderate and can slip appropriately → interlayer slip effectively dissipates impact energy during impact → V50 is increased and back convexity is reduced; 2. Polycarbonate segments contain carbonate bonds in their molecular structure, which significantly improves their hydrolysis resistance compared to polyether segments. This results in higher film performance retention under humid heat aging conditions and a humid heat aging retention rate of over 90.8%. 3. The polyurethane-acrylate copolymer network and aziridine external crosslinking form a composite crosslinking system → the cohesive strength and interfacial adhesion of the film are enhanced simultaneously → peel strength, initial tack and holding power are comprehensively improved.

[0018] Most importantly, it is generally accepted in the art that reducing the surface energy of an adhesive film usually leads to a decrease in the interfacial thermodynamic adhesion work between the adhesive and the fiber, which in turn manifests as a decrease in peel strength—that is, there is an inherent contradiction between "surface energy and adhesive force." However, this invention, through a gradient structure design, achieves a 180° peel strength of 4.5 N / 25 mm while maintaining an adhesive film surface energy as low as 30.2 mN / m. This is achieved by relying on the excellent bulk viscoelastic dissipation capability (elongation at break up to 680%) provided by the polycarbonate segments in the gradient structure. In other words, the decrease in interfacial thermodynamic adhesion work is compensated for by enhancing the bulk energy dissipation during the peeling process, completely breaking the technical prejudice in the art that "a decrease in surface energy inevitably leads to a decrease in adhesive strength." At the same time, the elongation at break reaches 680%, the moisture heat retention rate reaches 92.3%, the V50 reaches 602 m / s, and the back convexity depth is only 26.8 mm. This achieves a simultaneous improvement in four effects: low surface energy, high elasticity, high adhesive strength, and high aging resistance, which is a comprehensive technical effect that is not readily apparent.

[0019] When the adhesive of this invention is applied to bulletproof UD fabric, its low surface energy characteristics reduce the interfacial adhesion strength between the layers, allowing moderate interlayer slippage to occur between the UD fabric layers under ballistic impact to dissipate impact energy. Meanwhile, the high elasticity ensures that the adhesive film does not break brittlely during the slippage process, thus preventing the UD fabric from disintegrating and giving the bulletproof UD fabric a wrapping layer effect.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 The bar charts show the comparison between the V50 ballistic limit and the back convex deformation depth of the bulletproof UD fabric in Embodiments 1-3 of the present invention.

[0022] Figure 2 This is a comparison diagram of the surface energy of Embodiment 1 and Comparative Example 1 of the present invention.

[0023] Figure 3 This is a comparison diagram of the peel strength of Example 1 and Comparative Example 1 of the present invention.

[0024] Figure 4 This is a comparison diagram of the initial adhesion of Embodiment 1 and Comparative Example 1 of the present invention.

[0025] Figure 5 This is a comparison chart of the elongation at break between Example 1 and Comparative Example 1 of the present invention.

[0026] Figure 6 This is a comparison diagram of the V50 ballistic limits of Embodiment 1 and Comparative Example 1 of the present invention.

[0027] Figure 7This is a comparison chart of the moisture and heat retention rates of Example 1 and Comparative Example 1 of the present invention.

[0028] Figure 8 This is a gradient diagram of the carbonate film from the surface to the interior, obtained by XPS depth analysis in Example 1.

[0029] Figure 9 This is a comparison chart of the peel test curves of the universal testing machine for Example 1 and Comparative Example 1.

[0030] Figure 10 The image shows the XPSC1s high-resolution spectrum of Example 1.

[0031] Figure 11 The time-series curves for temperature and humidity in an 85°C / 85%RH humid heat aging chamber for 1000 hours are shown.

[0032] Figure 12 The bar chart shows the comparison of peel strength and retention rate of the four samples before and after wet heat aging in Examples 1-3 and Comparative Example 1.

[0033] Figure 13 The viscosity curves of the adhesives in Examples 1-3 at 25°C are shown as a function of rotor speed.

[0034] Figure 14 The mean and dispersion of the Shore A hardness measurements at 8 points are compared for the four samples in Examples 1-3 and Comparative Example 1.

[0035] Figure 15 This is an image of a droplet with a water contact angle of 78.5° in Example 1.

[0036] Figure 16 This is an image of a droplet with a diiodomethane contact angle of 52.3°, as shown in Example 1.

[0037] Figure 17 This is a droplet image with a water contact angle of 45.2°, as shown in Comparative Example 1.

[0038] Figure 18 This is an image of a droplet with a diiodomethane contact angle of 28.7°, as shown in Comparative Example 1. Detailed Implementation

[0039] The raw materials used in this invention are all commercially available industrial-grade conventional raw materials with a purity of ≥98%. Among them, the number-average molecular weight of polycarbonate glycol is 1000 and the number-average molecular weight of polypropylene glycol is 2000. Both are common industrial grades and can be purchased by technicians through conventional commercial channels.

[0040] Example 1 A water-based adhesive for bulletproof UD fabric, comprising the following components by weight: 8 parts of polycarbonate-based prepolymer (PCDL-IPDI, NCO content 5.8wt%), 35 parts of polypropylene glycol PPG-2000, 16 parts of isophorone diisocyanate IPDI, 25 parts of butyl acrylate BA, 1.5 parts of hydroxyethyl acrylate HEA, 3 parts of dimethylolpropionic acid DMPA, 1.2 parts of triethylamine TEA, 0.3 parts of aziridine crosslinking agent, 0.2 parts of polyether-modified siloxane defoamer, and 210 parts of deionized water.

[0041] The bulletproof UD fabric is prepared using a water-based adhesive, and the process includes the following steps: Step 1: Polyhexanediol (number average molecular weight 1000) was vacuum dehydrated at 110°C and -0.08 MPa for 1.5 hours. The temperature was then lowered to 80°C, and isophorone diisocyanate (IPDI) was added. The molar ratio of polyhexanediol to IPDI was 1:2. The mixture was reacted at 80°C for 3 hours under nitrogen protection. The NCO content was monitored in real time using di-n-butylamine titration. The NCO content of the product was controlled to be 5.8 wt%. The temperature was then lowered to 40°C and the product was discharged to obtain polycarbonate-based prepolymer (PCDL-IPDI, NCO content 5.8 wt%) for later use.

[0042] Step 2: Dehydrate 35 parts of polypropylene glycol PPG-2000 under vacuum at 110°C and -0.08MPa for 1.5 hours. Cool down to 80°C, add 16 parts of isophorone diisocyanate IPDI and 8 parts of the above polycarbonate-based prepolymer (PCDL-IPDI, NCO content 5.8wt%), and stir for 2 hours. Then add 3 parts of dimethylolpropionic acid DMPA and 5-10wt% of acetone (based on the total mass of polycarbonate-based prepolymer, polypropylene glycol, and diisocyanate), and continue to react for 1.5 hours to reduce viscosity.

[0043] Step 3: Cool down to 45℃, add 1.2 parts of triethylamine (TEA), stir and neutralize for 15 minutes; disperse at 1500 rpm high-speed shear for 10-20 minutes, add 210 parts of deionized water for dispersion, and add 0.2 parts of polyether-modified siloxane defoamer during dispersion.

[0044] Step 4: Add 25 parts of butyl acrylate (BA) and 1.5 parts of hydroxyethyl acrylate (HEA), and add 0.3-0.8 wt% of ammonium persulfate initiator, which is a 5-10 wt% aqueous solution and is not included in the aforementioned weight components. Perform a free radical copolymerization reaction at 65°C until the system viscosity stabilizes (viscosity fluctuation at 65°C does not exceed ±5% / 30 min), and the reaction endpoint is determined by visually observing no monomer droplets flowing back into the condenser. After the reaction, cool to room temperature, add 0.3 parts of aziridine crosslinking agent, and adjust the pH to 7.2. Remove acetone under reduced pressure (vacuum degree -0.08 MPa, temperature 40°C, removal time 1 h).

[0045] Example 2 A water-based adhesive for bulletproof UD fabric, comprising the following components by weight: 12 parts of polycarbonate-based prepolymer (PCDL-HDI, NCO content 6.3wt%), 30 parts of polypropylene glycol PPG-2000, 18 parts of hexamethylene diisocyanate HDI, 22 parts of butyl acrylate BA, 1 part of hydroxyethyl acrylate HEA, 3.5 parts of dimethylolpropionic acid DMPA, 1.5 parts of N-methylmorpholine NMM, 0.3 parts of aziridine crosslinking agent, 0.2 parts of defoamer, and 219 parts of deionized water.

[0046] The bulletproof UD fabric is prepared using a water-based adhesive, and the process includes the following steps: Step 1: Polybutylene carbonate diol (number average molecular weight 1000) was vacuum dehydrated at 110℃ and a vacuum degree of -0.09MPa for 1.5 hours. The temperature was then lowered to 80℃, and hexamethylene diisocyanate (HDI) was added at a molar ratio of 1:2. The mixture was reacted at 80℃ for 3 hours under nitrogen protection. The NCO content was monitored in real time using di-n-butylamine titration to control the NCO content of the product to 6.3wt%. The product was then cooled to 40℃ and discharged to obtain polycarbonate-based prepolymer (PCDL-HDI, NCO content 6.3wt%) for later use.

[0047] Step 2: Dehydrate 30 parts of polypropylene glycol PPG-2000 under vacuum at 110°C and -0.09MPa for 1.5 hours, cool down to 80°C, add 18 parts of HDI and 12 parts of the above polycarbonate-based prepolymer, and stir for 2 hours; then add 3.5 parts of DMPA and 5-10 wt% of acetone (based on the total mass of polycarbonate-based prepolymer, polypropylene glycol, and diisocyanate), and continue to react for 1.5 hours to reduce viscosity.

[0048] Step 3: Cool down to 45℃, add 1.5 parts of N-methylmorpholine (NMM), stir and neutralize for 15 minutes; disperse at 1500 rpm high-speed shear for 10-20 minutes, add 219 parts of deionized water for dispersion, and add 0.2 parts of polyether modified siloxane defoamer during the dispersion process.

[0049] Step 4: Add 22 parts of butyl acrylate (BA) and 1 part of hydroxyethyl acrylate (HEA), and add 0.3-0.8 wt% of ammonium persulfate initiator, which is a 5-10 wt% aqueous solution and is not included in the aforementioned weight components. Perform a free radical copolymerization reaction at 65°C until the system viscosity stabilizes (viscosity fluctuation at 65°C does not exceed ±5% / 30 min), and the reaction endpoint is indicated by visually observing no monomer droplets flowing back into the condenser. After the reaction, cool to room temperature, add 0.3 parts of aziridine crosslinking agent, and adjust the pH to 7.3. Remove acetone under reduced pressure (vacuum degree -0.09 MPa, temperature 45°C, removal time 1.5 h).

[0050] Example 3 A water-based adhesive for bulletproof UD fabric, comprising the following components by weight: 5 parts of polycarbonate-based prepolymer (PCDL-TMDI, NCO content 5.9wt%), 40 parts of polypropylene glycol PPG-2000, 14 parts of 2,2,4-trimethylhexamethylene diisocyanate TMDI, 28 parts of butyl acrylate BA, 2 parts of hydroxyethyl acrylate HEA, 2.5 parts of dimethylolpropionic acid DMPA, 1.0 part of triethylamine TEA, 0.4 parts of aziridine crosslinking agent, 0.1 parts of defoamer, and 193 parts of deionized water.

[0051] The bulletproof UD fabric is prepared using a water-based adhesive, and the process includes the following steps: Step 1: Polypentyl carbonate diol (number average molecular weight 1000) was vacuum dehydrated at 110℃ and under a vacuum of -0.095MPa for 1.5 hours. The temperature was then lowered to 80℃, and 2,2,4-trimethylhexamethylene diisocyanate (TMDI) was added at a molar ratio of 1:2. The mixture was reacted at 80℃ for 3 hours under nitrogen protection. The NCO content was monitored in real time using di-n-butylamine titration. The NCO content of the product was controlled to be 5.9wt%. The temperature was then lowered to 40℃ and the product was discharged to obtain polycarbonate-based prepolymer (PCDL-TMDI, NCO content 5.9wt%) for later use.

[0052] Step 2: Dehydrate 40 parts of polypropylene glycol PPG-2000 under vacuum at 110°C and -0.095MPa for 1.5 hours, cool down to 80°C, add 14 parts of TMDI and 5 parts of the above polycarbonate-based prepolymer, and stir for 2 hours; then add 2.5 parts of DMPA and 5-10 wt% of acetone (based on the total mass of polycarbonate-based prepolymer, polypropylene glycol, and diisocyanate), and continue to react for 1.5 hours to reduce viscosity.

[0053] Step 3: Cool down to 45℃, add 1.0 part of triethylamine (TEA), stir and neutralize for 15 minutes; disperse at 1500 rpm high-speed shear for 10-20 minutes, add 193 parts of deionized water for dispersion, and add 0.1 parts of polyether-modified siloxane defoamer during dispersion.

[0054] Step 4: Add 28 parts of butyl acrylate (BA) and 2 parts of hydroxyethyl acrylate (HEA), and add 0.3-0.8 wt% of ammonium persulfate initiator, which is a 5-10 wt% aqueous solution and is not included in the aforementioned weight components. Perform a free radical copolymerization reaction at 65°C until the system viscosity stabilizes (viscosity fluctuation at 65°C does not exceed ±5% / 30 min), and the reaction endpoint is indicated by visually observing no monomer droplets flowing back into the condenser. After the reaction, cool to room temperature, add 0.4 parts of aziridine crosslinking agent, and adjust the pH to 7.1. Remove acetone under reduced pressure (vacuum degree -0.095 MPa, temperature 50°C, removal time 2 h).

[0055] Performance testing methods The solid content was determined in accordance with GB / T2793-1995 standard.

[0056] Viscosity was measured using a rotational viscometer at 25°C.

[0057] pH values ​​were measured using a pH meter at 25°C.

[0058] Surface energy was measured using deionized water and diiodomethane as test liquids, and the Owens-Wendt-Kaelble method was used to calculate the surface energy of the film using an OCA20 contact angle measuring instrument (Dataphysics, Germany).

[0059] like Figures 15-18 Contact angle droplet images of Example 1 and Comparative Example 1 are shown respectively. Figure 15 The image shows the water contact angle of the film in Example 1. The contact angle was measured to be 78.5°, indicating that the film surface has low hydrophilicity. Figure 16 The image shows the diiodomethane contact angle of the film from Example 1, measured to be 52.3°. Figure 15 and Figure 16 The contact angle data, calculated using the Owens-Wendt-Kaelble method, yielded a surface energy of 30.2 mN / m for the film in Example 1. Figure 17 The droplet image shows the water contact angle of the film in Comparative Example 1. The measured contact angle is 45.2°, which is significantly lower than 78.5° in Example 1, indicating that the film surface has higher hydrophilicity when it does not contain polycarbonate segments. Figure 18 The image shows the contact angle of the diiodomethane droplet in the film of Comparative Example 1, with a measured contact angle of 28.7°. Based on... Figure 17 and Figure 18 The contact angle data calculated for Comparative Example 1 showed a surface energy of 40.5 mN / m, significantly higher than that of Example 1. The difference in contact angle and surface energy between Example 1 and Comparative Example 1 directly verifies that the enrichment of carbonate segments on the film surface effectively reduces the surface energy, and this reduction is mainly reflected in the dispersive component, consistent with the non-polar characteristics of carbonate segments. Test conditions: OCA20 contact angle measuring instrument (Dataphysics, Germany), temperature 25°C, test liquids were deionized water and diiodomethane.

[0060] The 180° peel strength was tested according to GB / T2792-2014 standard using a universal testing machine at a tensile speed of 300 mm / min, to test the 180° peel strength of the film to the PE substrate.

[0061] Initial tack was tested according to the rolling ball method in GB / T4852-2002. Holding tack was tested according to GB / T4851-2014 under a 1kg load.

[0062] Shore A hardness was determined according to GB / T531.1-2008 standard.

[0063] Elongation at break was determined according to GB / T528-2009 standard, with a tensile speed of 500 mm / min. Moist heat aging resistance was tested after 1000 hours at 85℃ / 85%RH, and the peel strength retention rate was then measured.

[0064] The V50 impact resistance performance was tested using a V50 fragmentation simulated projectile in accordance with MIL-STD-662F. The projectile specification was 1.1gFSP (17-grain Chisel-nose projectile), and the backing material was RomaPlastilina No.1. An 8-layer UHMWPEUD fabric sample (Dyneema SK76400D fiber, 0° / 90° orthogonal layup, hot pressing conditions 90℃×15min×3MPa) was used, and the back convex deformation depth was tested simultaneously.

[0065] The performance test data is shown in Table 1 below: Table 1

[0066] In Example 1, under XPS testing at a 15° angle, the area of ​​the carbonate sub-peak (~289.4 eV) obtained by XPS C1s peak fitting on the film surface accounted for 11.5 at; in XPS depth profiling from 15° to 75°, the carbonate content showed a decreasing gradient from the surface to the interior, and the surface / bulk carbonate concentration ratio was 1.51.

[0067] like Figure 8As shown, XPS (X-ray photoelectron spectroscopy, excitation source AlKα, pass energy 50 eV) was used to perform variable-angle depth profiling on the film of Example 1. At angles of 15°, 45°, and 75°, the area proportions of the characteristic sub-peaks of carbonate were 11.5 at, 9.5 at, and 7.6 at, respectively, with a surface / bulk concentration ratio of 1.51, confirming a gradient structure where the carbonate content decreases from the surface to the interior. Figure 10 As shown, after peak fitting, the XPS C1s high-resolution spectra of the film in Example 1 at different angles revealed a regular change in the three characteristic peaks CC / CH (284.8 eV), CO (286.3 eV), and OC=O (289.0 eV) as the angle increased. The area percentage of the OC=O peak, representing carbonate groups, decreased from 11.5 at% at 15° to 7.6 at% at 75°, quantitatively revealing the surface enrichment behavior of carbonate groups. Specific data are shown in Table 2 below. Table 2

[0068] Comparative Example 1 The polycarbonate-based prepolymer in Example 1 was replaced with an equal amount of polypropylene glycol PPG-2000 (8 parts), with the remaining composition the same as in Example 1, specifically: 43 parts polypropylene glycol PPG-2000, 16 parts isophorone diisocyanate (IPDI), 25 parts butyl acrylate (BA), 1.5 parts hydroxyethyl acrylate (HEA), 3 parts dimethylolpropionic acid (DMPA), 1.2 parts triethylamine (TEA), 0.3 parts aziridine crosslinking agent, 0.2 parts polyether-modified siloxane defoamer, and 210 parts deionized water. The total solids content was 90.2 parts, and the solid content was 30.0 wt%.

[0069] The preparation process is the same as in Example 1, but without the addition of polycarbonate-based prepolymer.

[0070] like Figures 2-7 The comparison results of Example 1 and Comparative Example 1 on various key performance indicators are presented respectively. Figure 2 For surface energy comparison, the Owens-Wendt-Kaelble method was used with an OCA20 contact angle meter (Dataphysics, Germany) and deionized water and diiodomethane as test liquids. The surface energy of Example 1 was 30.2 mN / m, and that of Comparative Example 1 was 40.5 mN / m, which verified the low surface energy characteristics caused by the enrichment of carbonate segments on the surface. Figure 3 For the 180° peel strength comparison, the tensile strength was measured on a universal testing machine at a tensile speed of 300 mm / min according to GB / T2792-2014 standard; Example 1 showed 4.5 N / 25 mm, and Comparative Example 1 showed 2.0 N / 25 mm. Figure 4For initial tack comparison, the rolling ball method of GB / T4852-2002 was used; Example 1 used a No. 11 ball and Comparative Example 1 used a No. 6 ball. Figure 5 For comparison of elongation at break, the tensile speed was measured at 500 mm / min according to GB / T528-2009 standard; Example 1 showed 680%, and Comparative Example 1 showed 350%. Figure 6 To compare the V50 ballistic limit and the back convexity deformation depth, tests were conducted using a 1.1g FSP projectile according to the MIL-STD-662F standard. The V50 of Example 1 was 602m / s and the back convexity was 26.8mm, while the V50 of Comparative Example 1 was 538m / s and the back convexity was 34.2mm. Figure 7 To compare the retention rate under damp heat, the peel strength retention rate was measured after aging at 85℃ / 85%RH for 1000 hours. Example 1 showed a retention rate of 92.3%, while Comparative Example 1 showed 70.0%. In summary, Example 1 significantly outperformed Comparative Example 1 in all indicators, confirming that the introduction of polycarbonate segments achieved a synergistic effect of low surface energy and high elasticity, and significantly improved the interfacial adhesion and damp heat aging resistance of the adhesive. The data comparison between Example 1 and Comparative Example 1 is shown in Table 3 below: Table 3

[0071] When using the adhesive prepared above according to the present invention, allow it to stand and mature at room temperature for 24 hours, and apply it at an amount of 8g / m². 2 The coating is uniformly applied to a 0° / 90° orthogonal layup of UHMWPE fibers and then hot-pressed and cured at 90℃ for 15 min at 3 MPa.

[0072] Finally, it should be noted that, according to the MIL-STD-662F standard, the V50 fragmentation simulation test was conducted with a 1.1g FSP projectile. The V50 value of the 8-layer UHMWPEUD fabric 0° / 90° cross-lay reached 572~618m / s (602m / s in Example 1, and 618m / s in Example 2), and the back convex deformation depth was 25.3~30.5mm (26.8mm in Example 1).

[0073] like Figure 1As shown in the bar chart, the comparison results of V50 ballistic limit and back convexity deformation depth of Examples 1-3 are intuitively displayed. Example 2 has the best overall performance (V50 618m / s, back convexity 25.3mm). Example 1 (V50 602m / s, back convexity 26.8mm) has performance close to that of Example 2. Example 3 (V50 572m / s, back convexity 30.5mm) also shows good ballistic performance. The test conditions were: 8 layers of UHMWPEUD fabric (Dyneema SK76400D fiber) were laid in 0° / 90° orthogonal layers, hot-pressed at 90℃×15min×3MPa, and tested with a 1.1gFSP (17-grain Chisel-nose bullet) bullet according to MIL-STD-662F standard. The backing material was Roma Plastilina No. 1.

[0074] The 180° peel strength reached 4.2~4.8N / 25mm (4.5N / 25mm in Example 1), the initial tack reached ball size 10~12 (ball size 11 in Example 1), and the holding time was over 24 hours, indicating that the bonding reliability between the adhesive and the fiber was significantly enhanced.

[0075] like Figure 9 As shown, a comparison of the 180° peel test curves of Example 1 and Comparative Example 1 reveals that, using a universal testing machine according to GB / T2792-2014 standard at a tensile speed of 300 mm / min, the average peel force of Example 1 was 4.50 N / 25 mm, and the curve showed a stable plateau region during the peeling process, indicating that the adhesive film continuously consumed energy during peeling. The average peel force of Comparative Example 1 was 2.00 N / 25 mm, with smaller curve fluctuations but significantly lower peel force. The interfacial adhesion strength of Example 1 was more than double that of Comparative Example 1.

[0076] Furthermore, the excellent hydrolysis resistance and thermal stability of polycarbonate segments endow the adhesive film with outstanding resistance to humid heat aging. After aging for 1000 hours at 85℃ / 85%RH, the peel strength retention rate reaches 92.3%, significantly improving the performance degradation problem of polyether-type polyurethane adhesives under high temperature and high humidity service environments. Meanwhile, this invention uses an aqueous system with deionized water as the dispersion medium, and only a small amount of acetone is used in the preparation process, which is removed under reduced pressure. It does not contain heavy metal catalysts such as organotin catalysts. The preparation process is simple and controllable, the four-step method operates under mild conditions, requires no high-temperature or high-pressure equipment, and is easy to implement for industrial production.

[0077] like Figures 11-14 The test results and physical property comparisons of the various tests in the damp heat aging test are presented respectively. Figure 11 The temperature and humidity time-series curves for the 85°C / 85%RH damp heat aging chamber over 1000 hours show that the temperature and humidity remained stable throughout the test period, verifying the reliability of the aging test conditions. Figure 12The bar chart shows the comparison of peel strength and retention rate of the four samples before and after humid heat aging in Examples 1-3 and Comparative Example 1. The peel strength retention rates of Examples 1-3 were 92.3%, 93.5%, and 90.8%, respectively, which were significantly higher than 70.0% of Comparative Example 1. This indicates that the introduction of polycarbonate segments significantly improved the film's resistance to humid heat aging. Figure 13 The viscosity curves of the adhesives in Examples 1-3 at 25°C are shown as a function of rotor speed. The viscosity decreases as the speed increases, exhibiting shear thinning behavior, which is beneficial for leveling and wetting in the coating process. Figure 14 The mean and dispersion of Shore hardness A measured at 8 points are compared for the four samples of Examples 1-3 and Comparative Example 1. The Shore hardness A of Examples 1-3 are 32, 28 and 35 respectively, which are all lower than 48 of Comparative Example 1. This indicates that the adhesive film of the present invention has better flexibility, which is beneficial to interlayer slippage energy dissipation during ballistic impact.

[0078] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing bulletproof UD fabric using a water-based adhesive, characterized in that, By weight, it includes the following components: 5-12 parts of polycarbonate-based prepolymer, 30-40 parts of polypropylene glycol with a number average molecular weight of 2000 14-18 parts of diisocyanate, 22-28 parts of butyl acrylate, 1-2 parts of hydroxyethyl acrylate Dimethylolpropionic acid 2.5~3.5 parts, Neutralizing agent 1.0~1.5 parts, Aziridine crosslinking agent 0.3~0.4 parts, 0.1-0.2 parts of polyether-modified siloxane defoamer. 193-219 parts of deionized water; The polycarbonate-based prepolymer is prepared by reacting polycarbonate diol with diisocyanate in a molar ratio of 1:2, and has an NCO content of 5.8~6.3 wt%. The polycarbonate diol is selected from at least one of polyhexanediol, polybutylene dicarbonate, and polypentylene dicarbonate, and has a number average molecular weight of 1000. The diisocyanate is selected from at least one of isophorone diisocyanate, hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate; The neutralizing agent is triethylamine and / or N-methylmorpholine; The preparation includes the following steps: Step 1: Dehydrate polycarbonate diol under vacuum at 110℃ and -0.08~-0.095MPa for 1.5 hours, cool down to 80℃, add diisocyanate at a molar ratio of 1:2, react at 80℃ for 3 hours under nitrogen protection, use di-n-butylamine titration to detect NCO content in real time, control the NCO content of the product to be 5.8~6.3wt%, cool down to 40℃ and discharge to obtain polycarbonate-based prepolymer for later use; Step 2: Dehydrate polypropylene glycol under vacuum at 110°C and a vacuum degree of -0.08 to -0.095 MPa for 1.5 hours, cool it down to 80°C, add diisocyanate and the polycarbonate-based prepolymer obtained in Step 1, and stir to react for 2 hours; then add dimethylolpropionic acid and acetone accounting for 5-10 wt% of the total mass of polycarbonate-based prepolymer, polypropylene glycol, and diisocyanate, and continue to react for 1.5 hours to reduce viscosity; Step 3: Cool down to 45℃, add neutralizing agent, stir and neutralize for 15 minutes; disperse at 1500rpm high speed shear for 10~20min, add deionized water for dispersion, and add polyether modified siloxane defoamer during dispersion. Step 4: Add butyl acrylate and hydroxyethyl acrylate, and add 0.3~0.8 wt% of ammonium persulfate initiator, which is a 5~10 wt% aqueous solution. The initiator is not included in the aforementioned weight components. Carry out a free radical copolymerization reaction at 65°C until the viscosity of the system fluctuates by ≤±5% within 30 minutes at 65°C and no monomer droplets are visually observed flowing back into the condenser. After the reaction, cool to room temperature, add aziridine crosslinking agent, and adjust the pH value to 7.1~7.

3. Remove acetone under reduced pressure, with a vacuum degree of -0.08~-0.095 MPa, a temperature of 40~50°C, and a removal time of 1~2 hours. Obtain the water-based adhesive for the bulletproof UD fabric.

2. A water-based adhesive for bulletproof UD fabric, characterized in that, It is prepared by the preparation method described in claim 1.

3. The water-based adhesive for bulletproof UD fabric according to claim 2, characterized in that, The adhesive film has a gradient structure in which the carbonate content decreases from the surface to the interior. The surface energy of the film is ≤31.5 mN / m, the elongation at break is ≥650%, and the Shore A hardness is ≤35.

4. A bulletproof UD fabric, characterized in that, It includes reinforcing fibers and a water-based adhesive as described in claim 2 or 3 for the bulletproof UD fabric; the bulletproof UD fabric is formed by the reinforcing fibers being impregnated with the adhesive and then arranged in a unidirectional parallel pattern.

5. The bulletproof UD fabric according to claim 4, characterized in that, The reinforcing fiber is ultra-high molecular weight polyethylene fiber.

6. The bulletproof UD fabric according to claim 4, characterized in that, The bulletproof UD fabric is made of 8 layers laid in an orthogonal pattern at 0° / 90° and hot-pressed at 90° for 15 min for 3 MPa.

7. A bulletproof product, characterized in that, It includes the bulletproof UD fabric as described in any one of claims 4 to 6.

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