Resin system for low-temperature-resistant prepreg filaments of low-temperature and high-pressure hydrogen storage cylinder

Abstract

The invention relates to the technical field of composite materials, and discloses a resin system for low-temperature-resistant prepreg filaments of a low-temperature and high-pressure hydrogen storage cylinder, and the resin system comprises the following components in parts by weight: 100 parts of a composite resin matrix, 25-60 parts of a composite curing agent, 1-2 parts of an accelerant and 2-20 parts of a composite toughening agent, wherein the composite toughening agent is obtained by mixing a flexible polymer and nano particles according to a weight part ratio of (1-20): (1-10); the flexible polymer is selected from at least one of a polyether block polymer L-61, polyether amine and polyamide, and the molecular weight of the flexible polymer is greater than 1500; the nano particles are selected from at least one of silicon dioxide, graphene, SiO2 / PU (polyurethane) core-shell particles and SiO2 / PMMA (polymethyl methacrylate) core-shell particles. According to the technical scheme provided by the invention, the resin system for winding the prepreg filaments by the dry method, which has both toughness and strength, can be provided.

Description

Technical Field

[0001] The present application relates to the technical field of composite materials, and in particular to a resin system for low-temperature resistant prepreg yarns for low-temperature and high-pressure hydrogen storage cylinders. Background Art

[0002] As a clean and efficient energy source, hydrogen has the potential to reduce greenhouse gas emissions and be widely used in transportation, industry and energy storage. However, low-temperature and high-pressure hydrogen storage technology (CcH2) faces challenges in storage and transportation safety and efficiency. In the design of low-temperature compressed hydrogen storage containers, the outer fiber composite material assumes the main load-bearing function, and its performance has a decisive influence on the overall safety of the container. Dry winding technology has shown good application prospects in the manufacture of such structures due to its advantages such as high product quality, excellent production efficiency and low environmental impact. However, the lack of low-temperature toughening resin systems limits its application, especially epoxy resins are very brittle at low temperatures and cannot meet the performance requirements of hydrogen storage containers. Summary of the Invention

[0003] The present application provides a resin system for low-temperature resistant prepreg yarns for low-temperature and high-pressure hydrogen storage cylinders, which achieves the technical effect of taking both toughness and strength into consideration.

[0004] In order to achieve the above objectives, the main technical solutions adopted in this application include: In a first aspect, an embodiment of the present application provides a resin system, which includes the following components in parts by weight: 100 parts of a composite resin matrix, 25-60 parts of a composite curing agent, 1-2 parts of an accelerator, and 2-20 parts of a composite toughening agent; wherein the composite toughening agent is obtained by mixing a flexible polymer and nanoparticles in a ratio of 1-20:1-10 by weight; the flexible polymer is selected from at least one of polyether block polymer L-61, polyetheramine, and polyamide, and the molecular weight of the flexible polymer is greater than 1500; the nanoparticles are selected from at least one of silica, graphene, SiO2 / PU core-shell particles, and SiO2 / PMMA core-shell particles.

[0005] The composite resin matrix in this embodiment is the main structural skeleton, which determines the basic properties of the resin system, including high thermal stability and mechanical strength. The accelerator synergistically controls the rate of the curing reaction. By adjusting the curing rate, premature curing can be avoided and the fluidity of the resin system during processing can be maintained. Especially for processes such as prepreg, it is very important to control the timing and rate of curing, which ensures the consistency and reliability of the resin system under different operating conditions. The addition of the composite toughening agent significantly improves the toughness of the resin system at low temperatures. At low temperatures, the resin usually becomes more brittle and prone to crack propagation. After the composite toughening agent is added, a strong multiple interpenetrating polymer network (IPN) structure is formed. The cross-linked network framework absorbs impact energy through the stretching and slippage of the flexible network composed of flexible polymer molecular chains, which can delay the propagation of cracks. Since the molecular weight of the flexible polymer in the composite toughening agent is greater than 1500, it indicates that it has sufficient chain length and mobility, and can still effectively absorb impact force even in low temperature environments.

[0006] Specifically, flexible polymers such as polyether block polymer L-61, polyetheramines, and polyamides can form multiple interpenetrating polymer networks (IPNs) with the composite resin matrix, strengthening the interfacial bonding of the composite resin matrix and providing a flexible buffer layer. This structure not only enhances the low-temperature toughness of the resin system but also improves its mechanical strength. The hydrogen bonding of polyamide further reduces the brittleness of the resin system at low temperatures and reduces molecular chain breakage. The addition of nanoparticles (such as SiO2 and graphene) enhances the strength and thermal stability of the resin system. Rigid nanoparticles such as silica help maintain the glass transition temperature (Tg) of the resin system by limiting excessive molecular chain movement at high temperatures and improving thermal stability. Furthermore, nanoparticles can deflect or blunt cracks, increasing the energy dissipation of crack propagation and further enhancing the material's crack resistance. In a resin system, SiO2 / PU or SiO2 / PMMA core-shell particles enhance the modulus of the composite resin matrix through their core (rigid SiO2), while the outer shell (PU or PMMA) helps form a gradient interface within the composite resin matrix, dispersing stress concentration and reducing the risk of crack propagation. Due to the unique structure of the core-shell particles, they enhance strength while avoiding the brittle failure that can result from rigid materials within the composite resin matrix. Thus, the flexible polymer provides low-temperature toughness, while the nanoparticles enhance the resin's strength, thermal stability, and crack resistance. This "rigid-flexible" toughening mechanism ensures both toughness at low temperatures and strength and stability at elevated temperatures or under load.

[0007] In one embodiment, the composite resin matrix is obtained by mixing resin A and resin B in a ratio of 70-90:10-30 by weight; the resin A is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and liquid phenolic resin; and the resin B is selected from at least one of alicyclic epoxy resin and flexible side chain epoxy resin.

[0008] In this embodiment, Resin A is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and liquid phenolic resin. Bisphenol A epoxy resin and bisphenol F epoxy resin have high crosslink density and mechanical strength, and low shrinkage after curing, making them suitable for applications requiring high strength and high modulus in low-temperature, high-pressure hydrogen storage bottles. Liquid phenolic resin provides high adhesion and good chemical resistance while reducing internal stress during the curing process. These Resins A form a dense network structure during the curing process, enabling good interfacial bonding with reinforcing fibers (such as carbon fibers), thereby improving the overall performance of the material.

[0009] Resin B is selected from at least one of a cycloaliphatic epoxy resin and a flexible side-chain epoxy resin. In cycloaliphatic epoxy resins (such as EHPE-3150), the epoxy groups are directly attached to the alicyclic rings, forming a rigid molecular structure with a high glass transition temperature (Tg) while maintaining a certain degree of toughness at low temperatures. Allyl glycidyl ether, by introducing a flexible chain segment, significantly reduces internal stress during the curing process and improves the low-temperature toughness of the composite resin matrix. These resins B have low viscosity and maintain good fluidity at low temperatures, facilitating fiber impregnation and molding processes.

[0010] Therefore, by reasonably controlling the ratio of resin A to resin B (70-90:10-30), a balance between high strength, low shrinkage, high adhesion and low-temperature toughness and high fluidity can be achieved, thereby meeting the comprehensive performance requirements of the final resin system under various complex working conditions.

[0011] In one embodiment, the bisphenol A epoxy resin is selected from at least one of E51 epoxy resin, E44 epoxy resin, and E42 epoxy resin; the bisphenol F epoxy resin is selected from at least one of YDF-161H epoxy resin and YDF-170 epoxy resin; the liquid phenolic resin is selected from at least one of F-51 phenolic resin and F-44 phenolic resin; the alicyclic epoxy resin is selected from at least one of EHPE-3150 resin, bis(7-oxabicyclo[4.1.0]3-heptylmethyl)adipate, and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate; and the flexible side chain epoxy resin is allyl glycidyl ether.

[0012] In this embodiment, the bisphenol A epoxy resin is selected from at least one of E51 epoxy resin, E44 epoxy resin, and E42 epoxy resin. It exhibits high crosslink density and mechanical strength, low shrinkage after curing, and a higher glass transition temperature (Tg). In a composite resin matrix, it provides excellent chemical resistance and low shrinkage, ensuring a stable structure during curing. The bisphenol F epoxy resin is selected from at least one of YDF-161H epoxy resin and YDF-170 epoxy resin, exhibiting low viscosity and a high glass transition temperature (Tg). The cycloaliphatic epoxy resin is selected from at least one of EHPE-3150 resin, bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate, and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate. It exhibits a high glass transition temperature (Tg), good low-temperature toughness, and low shrinkage after curing, making it suitable for composite materials used in low-temperature and high-pressure environments, such as hydrogen storage cylinders and aerospace structural components. The flexible side-chain epoxy resin is allyl glycidyl ether, which has good low-temperature toughness and low viscosity, ensuring that the material maintains good performance in low-temperature environments. By properly selecting and mixing these resins, a balance between high strength, high toughness, high heat resistance, and low-temperature performance can be achieved in the composite material.

[0013] In one embodiment, the composite curing agent is obtained by mixing curing agent A and curing agent B in a ratio of 5-30 parts by weight:12-40; the curing agent A is a latent amine curing agent; wherein the latent amine curing agent is selected from at least one of dicyandiamide, isophoronediamine, 1,2-cyclohexanediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, and m-phenylenediamine; the curing agent B is an acid anhydride curing agent; wherein the acid anhydride curing agent is selected from at least one of methyl nadic anhydride, phthalic anhydride, and hexahydrophthalic anhydride.

[0014] The curing agent A described in this embodiment is a latent amine curing agent. Curing agent A is latent at low temperatures and can be activated at appropriate temperatures to control the rate of the curing reaction. This allows the resin system to cure slowly at low temperatures and avoid premature curing.

[0015] The curing agent B is selected from at least one of methyl nadic anhydride, phthalic anhydride, and hexahydrophthalic anhydride, and forms a cross-linked network with a high glass transition temperature (Tg) during the curing process to improve the thermal stability and mechanical properties of the resin system.

[0016] Therefore, by mixing curing agent A and curing agent B in a ratio of 5-30 parts by weight:12-40 parts by weight, the processability of the resin system in a low temperature environment is ensured and the rheological properties of the resin system are optimized to adapt to the dry winding process.

[0017] In one embodiment, the accelerator is selected from at least one of an organic urea accelerator, a tertiary amine accelerator, and a boron amine complex; wherein the organic urea accelerator is selected from at least one of UR200, UR300, and UR500; and the tertiary amine accelerator is selected from at least one of DMP-30 and BDMA.

[0018] The main function of the accelerator in this embodiment is to accelerate the rate of the curing reaction, reduce the curing temperature, shorten the curing time, and thus improve production efficiency. By selecting a suitable accelerator, the curing efficiency of the epoxy resin system can be significantly improved, the curing temperature can be reduced, and the curing time can be shortened.

[0019] In a second aspect, an embodiment of the present application provides a method for preparing the resin system described above, the method comprising: Mixing resin A and resin B, heating to 60-100° C. and mixing at a speed of 200-1000 rpm for 10-20 minutes to obtain a composite resin matrix; Mix curing agent A and curing agent B, heat to 40-80°C and mix at a speed of 500-800 rpm for 15-20 minutes to obtain a composite curing agent; The flexible polymer and the nanoparticles are mixed, heated to 80-160° C., and mixed at a rotation speed of 1500-2000 rpm for 10-20 minutes to obtain a composite toughening agent; The composite resin matrix, the composite curing agent, the composite toughening agent and the accelerator are mixed, heated to 60-100° C. and mixed for 20-30 minutes, and then ultrasonically dispersed and vacuum defoamed to obtain a resin system.

[0020] The mixture of resin A and resin B in this embodiment can combine the advantages of both. Resin A provides high strength and low shrinkage, while resin B provides low-temperature toughness and high fluidity. Heating to 60-100°C can reduce the viscosity of the resin, making it easier to mix evenly. Mix at a speed of 200-1000rpm for 10-20min to ensure that the two resins are fully mixed to form a uniform composite resin matrix. Curing agent A provides latent curing ability and needs to start the curing reaction at a certain temperature to ensure the processability and storage stability of the resin system. Curing agent B provides high Tg and good thermal stability, while reducing viscosity, so that the resin system and the fiber are fully infiltrated. Mix at a speed of 500-800rpm for 15-20min to ensure that the two curing agents are fully mixed to form a uniform composite curing agent. The addition of flexible polymer significantly improves the low-temperature toughness of the resin system, ensuring that the resin system can still maintain good performance in low-temperature environments. The addition of nanoparticles enhances the crack resistance of the material and avoids crack propagation. By heating and high-speed stirring, ensure that the flexible polymer and nanoparticles are fully mixed to form a uniform composite toughening agent. Mix all components together to ensure they are fully dispersed and form a homogeneous resin system.

[0021] In a third aspect, an embodiment of the present application provides a method for preparing a prepreg, the method comprising: After adding the resin system to the dipping tank and heating it to 50°C, the heated resin system is evenly spread on the release paper and fully impregnated with the reinforcing fiber to obtain a prepreg; wherein the resin system is the resin system described above or the resin system prepared by the resin system preparation method described above; A release paper is laid flat on the surface of the prepreg, the prepreg is pre-cured, and then cooled. After cooling, the release paper on the surface is peeled off, a polyethylene film is laid on the surface, and the prepreg is rolled up to obtain the prepreg.

[0022] The resin system used in this embodiment has high strength, low-temperature toughness, high Tg and good process adaptability, and is suitable for the preparation of prepreg yarns. Heating to 50°C can reduce the viscosity of the resin, making it easier to flow and impregnate the fibers. Spread the reinforcing fibers (such as carbon fibers and glass fibers) evenly on the resin, and ensure that the fibers are fully impregnated with the resin. Precuring is to partially cure the resin so that it has a certain shape and strength, but it is not yet fully cured. This step can prevent the fibers from shifting during subsequent operations, and at the same time facilitates subsequent cooling and molding. The release paper laid flat on the surface can protect the surface of the prepreg yarn and prevent it from being contaminated or damaged during the precuring process. After the prepreg yarn is cooled to room temperature, the release paper on the surface is peeled off. A layer of polyethylene film is laid on the surface of the prepreg yarn. The polyethylene film can protect the surface of the prepreg yarn and prevent it from being contaminated or damaged during the winding process. The prepreg yarn after winding can be stored at room temperature for at least 60 days and has good storage stability.

[0023] In one embodiment, the pre-curing temperature is 120° C., the heating time is 20-30 min, and the prepreg obtained by winding is placed at room temperature for at least 60 days.

[0024] By controlling the precuring temperature and time, this embodiment ensures that the prepreg has good shape stability, thermal stability, and fiber-resin bonding properties. Furthermore, by allowing it to stand at room temperature for at least 60 days, a high-performance composite material suitable for low-temperature, high-pressure environments can be produced.

[0025] In a fourth aspect, an embodiment of the present application provides an application of a prepreg, and the prepreg produced by the above-mentioned prepreg preparation method is applied to a low-temperature and high-pressure hydrogen storage cylinder.

[0026] In one embodiment, the prepreg is subjected to temperature-raising and curing, and then cooled to obtain a low-temperature and high-pressure hydrogen storage cylinder; wherein the temperature-raising and curing conditions are: 100°C / 1h+120°C / 1h+130°C / 1h.

[0027] In this embodiment, 100°C / 1 hour is the initial curing stage to eliminate the original internal thermal stress. 120°C / 1 hour is the intermediate curing stage, which further strengthens the cross-linking network on the basis of pre-curing of the prepreg and improves the mechanical properties of the material. 130°C / 1 hour is the post-curing stage to ensure complete curing, and then cool to room temperature with the furnace to form a stable low-temperature high-pressure hydrogen storage cylinder. By curing by increasing the temperature in stages, the rate of the curing reaction can be effectively controlled to avoid internal stress concentration and defects caused by too fast curing. The gradually increasing temperature can ensure that the curing agent in the resin system fully reacts to form a cross-linking network with a high Tg, thereby improving the thermal stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific implementation or the description of the prior art.

[0029] Figure 1 The temperature-viscosity relationship curve of the resin system prepared in Example 1 and Comparative Example 8 is shown. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of this application.

[0031] Hydrogen energy, as a clean, environmentally friendly, and efficient form of energy, is gaining increasing attention worldwide. It not only effectively reduces greenhouse gas emissions but also demonstrates enormous potential for application in a wide range of fields, including transportation, industrial production, and energy storage. However, the storage and transportation of hydrogen still face numerous challenges, particularly regarding the safety and efficiency of hydrogen storage under low-temperature and high-pressure conditions. Cryogenic compressed hydrogen storage (CcH2), a key technology, offers high hydrogen storage density and flexible refueling methods, providing an effective solution for the widespread application of hydrogen energy.

[0032] Material selection is crucial in the design of cryogenic compressed hydrogen storage vessels. While widely used, traditional wet winding technology suffers from issues such as uneven resin impregnation, environmental pollution, and low production efficiency. Consequently, dry winding has emerged as an advanced alternative to wet winding, offering significant advantages in improving production efficiency and reducing environmental pollution. By pre-impregnating the fiber with resin, dry winding avoids the issues of resin volatilization and uneven impregnation encountered in wet winding, thereby improving the material's strength and overall performance.

[0033] However, despite the potential of dry winding technology for improving the performance of hydrogen storage materials, there is still a lack of low-temperature toughening resin systems suitable for dry winding in low-temperature, high-pressure hydrogen storage containers. Traditional epoxy resins exhibit strong brittleness at low temperatures, making it difficult to meet the dual toughness and strength requirements of low-temperature, high-pressure hydrogen storage containers.

[0034] Therefore, how to provide a resin system for dry winding prepreg that can balance toughness and strength is a technical problem that urgently needs to be solved.

[0035] In order to better explain the present application and facilitate understanding, the present application is described in detail below through specific embodiments. In the examples, if not otherwise specified, parts are expressed by weight, and the raw materials in the examples of the present application are purchased through commercial channels.

[0036] Example 1 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E51 epoxy resin, YDF-161H epoxy resin and EHPE-3150 resin are mixed, heated to 80° C. and mixed at a rotation speed of 800 rpm for 15 minutes to obtain a composite resin matrix.

[0037] Step S2: dicyandiamide and nadic methyl anhydride are mixed, heated to 65° C., and mixed at a rotation speed of 600 rpm for 16 minutes to obtain a composite curing agent.

[0038] Step S3: Mix the polyether block polymer L-61 with the SiO2 / PU core-shell particles, heat to 100°C and mix at a rotation speed of 1500 rpm for 15 minutes to obtain a composite toughening agent.

[0039] Step S4: mixing the composite resin matrix, the composite curing agent, the composite toughening agent and UR500, heating to 80° C. and mixing for 25 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0040] Example 2 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E44 epoxy resin, F-44 phenolic resin and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate were mixed, heated to 60° C. and mixed at a rotation speed of 600 rpm for 16 minutes to obtain a composite resin matrix.

[0041] Step S2: mixing isophorone diamine and phthalic anhydride, heating to 45° C. and mixing at a rotation speed of 500 rpm for 18 minutes to obtain a composite curing agent.

[0042] Step S3: mixing the polyetheramine with the SiO2 / PMMA core-shell particles, heating to 150°C and mixing at a rotation speed of 1800 rpm for 12 minutes to obtain a composite toughening agent.

[0043] Step S4: mixing the composite resin matrix, composite curing agent, composite toughening agent and DMP-30, heating to 60° C. and mixing for 30 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0044] Example 3 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E42 epoxy resin, YDF-170 epoxy resin and allyl glycidyl ether are mixed, heated to 75° C. and mixed at a rotation speed of 1000 rpm for 20 minutes to obtain a composite resin matrix.

[0045] Step S2: Mix diaminodiphenylmethane and hexahydrophthalic anhydride, heat to 40° C., and mix at a rotation speed of 800 rpm for 15 minutes to obtain a composite curing agent.

[0046] Step S3: mixing polyamide and graphene, heating to 160° C. and mixing at a rotation speed of 1500 rpm for 10 minutes to obtain a composite toughening agent.

[0047] Step S4: mixing the composite resin matrix, composite curing agent, composite toughening agent and DMP-30, heating to 100° C. and mixing for 20 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0048] Example 4 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E51 epoxy resin, F-51 phenolic resin and bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate were mixed, heated to 80° C. and mixed at a rotation speed of 400 rpm for 12 minutes to obtain a composite resin matrix.

[0049] Step S2: 1,2-cyclohexanediamine and phthalic anhydride are mixed, heated to 80° C., and mixed at a rotation speed of 650 rpm for 15 minutes to obtain a composite curing agent.

[0050] Step S3: mixing the polyether block polymer L-61 with silicon dioxide, heating the mixture to 80° C. and mixing the mixture at a rotation speed of 1500 rpm for 20 minutes to obtain a composite toughening agent.

[0051] Step S4: mixing the composite resin matrix, the composite curing agent, the composite toughening agent and UR500, heating to 70° C. and mixing for 22 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0052] Example 5 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E44 epoxy resin and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate were mixed, heated to 90° C., and mixed at a rotation speed of 600 rpm for 18 minutes to obtain a composite resin matrix.

[0053] Step S2: mixing isophorone diamine and hexahydrophthalic anhydride, heating to 55° C. and mixing at a rotation speed of 700 rpm for 17 minutes to obtain a composite curing agent.

[0054] Step S3: mixing polyamide with SiO2 / PU core-shell particles, heating to 130°C and mixing at a rotation speed of 1700 rpm for 18 minutes to obtain a composite toughening agent.

[0055] Step S4: mixing the composite resin matrix, the composite curing agent, the composite toughening agent and UR300, heating to 90° C. and mixing for 21 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0056] Example 6 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E42 epoxy resin and EHPE-3150 resin are mixed, heated to 60° C., and mixed at a rotation speed of 200 rpm for 20 minutes to obtain a composite resin matrix.

[0057] Step S2: diaminodiphenyl sulfone and methyl nadic anhydride are mixed, heated to 80° C., and mixed at a rotation speed of 800 rpm for 15 minutes to obtain a composite curing agent.

[0058] Step S3: mixing the polyetheramine with the SiO2 / PMMA core-shell particles, heating to 130°C and mixing at a rotation speed of 1600 rpm for 10 minutes to obtain a composite toughening agent.

[0059] Step S4: mixing the composite resin matrix, the composite curing agent, the composite toughening agent and UR200, heating to 85° C. and mixing for 27 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0060] Example 7 The resin system of this embodiment is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E44 epoxy resin, YDF-161H epoxy resin and allyl glycidyl ether are mixed, heated to 65° C. and mixed at a rotation speed of 400 rpm for 18 minutes to obtain a composite resin matrix.

[0061] Step S2: m-phenylenediamine and methyl nadic anhydride are mixed, heated to 45° C., and mixed at a rotation speed of 750 rpm for 20 minutes to obtain a composite curing agent.

[0062] Step S3: mixing polyamide with SiO2 / PMMA core-shell particles, heating to 140°C and mixing at a rotation speed of 1700 rpm for 11 minutes to obtain a composite toughening agent.

[0063] Step S4: mixing the composite resin matrix, composite curing agent, composite toughening agent and BDMA, heating to 80° C. and mixing for 26 minutes, and then ultrasonically dispersing and vacuum degassing to obtain a resin system.

[0064] Comparative Example 1 In this comparative example, the "composite toughening agent" is removed from Example 1, and the preparation method is the same as that of Example 1 to obtain a resin system.

[0065] Comparative Example 2 This comparative example is based on Example 1, except for the “nanoparticles”. The preparation method is the same as that of Example 1, and a resin system is obtained.

[0066] Comparative Example 3 In this comparative example, the "flexible polymer" is removed from Example 1, and the preparation method is the same as that of Example 1 to obtain a resin system.

[0067] Comparative Example 4 In this comparative example, 20 parts of polyetheramine and 5 parts of SiO2 / PMMA core-shell particles were added to the same as in Example 2. The preparation method was similar to that in Example 2 to obtain a resin system.

[0068] Comparative Example 5 In this comparative example, 5 parts of polyetheramine and 40 parts of SiO2 / PMMA core-shell particles were added to the Example 2. The preparation method was similar to that of the Example 2 to obtain a resin system.

[0069] Comparative Example 6 The resin system of this comparative example is prepared from the following raw materials: The preparation method is as described in Example 1 to prepare a resin system.

[0070] Comparative Example 7 The resin system of this comparative example is prepared from the following raw materials: The preparation method is as described in Example 4 to obtain a resin system.

[0071] Comparative Example 8 The resin system of this comparative example is prepared from the following raw materials: The preparation method of the resin system is as follows: Step S1: E51 epoxy resin is heated to 90° C., stirred at 1000 rpm for 20 minutes, subjected to vacuum defoaming treatment for 30 minutes, and cooled to 50° C. to obtain component A.

[0072] Step S2: Nadic methyl anhydride, phenyl glycidyl ether, DPM-30 and polyethylene glycol are mixed, stirred at 700 rpm for 20 minutes, and then vacuum degassed for 30 minutes to obtain component B.

[0073] Step S3, mixing component A and component B in a weight ratio of 1:1 to obtain a prepolymer, casting it in a mold, and curing it by heating; the heating curing conditions are: 150℃ / 2h+180℃ / 4h+200℃ / 4h+230℃ / 2h. After curing is completed, cool it to room temperature in the furnace, demold, and obtain a resin system.

[0074] The process performance of the resin systems prepared in Examples 1-7 above was evaluated, and the test was carried out according to the standard method. The performance statistics of the above resin systems are shown in Table 1: Table 1 Process performance evaluation results of resin system As shown in Table 1, the gel times for Examples 1-7 ranged from 25 to 30 minutes, indicating that the resin system rapidly begins to cure at 120°C but is not yet fully cured. This rapid gelation allows the resin system to quickly form a desired shape during processing while maintaining a certain level of fluidity, thus avoiding operational difficulties caused by premature curing.

[0075] The glass transition temperatures (Tg) of Examples 1-7 range from 142°C to 155°C, demonstrating the high thermal stability of the resin system. A high Tg value means the material maintains good mechanical properties even at high temperatures, which is particularly important for applications in low-temperature, high-pressure hydrogen storage cylinders. In this application scenario, the material must maintain its performance at high temperatures. In the heating and vacuuming process, the heating process serves two primary purposes: First, heating increases the kinetic energy of gas molecules, making it easier for them to diffuse out of the resin matrix. This process is necessary to remove residual gases and volatile organic compounds from the hydrogen storage cylinder to ensure the cylinder's seal and gas purity. Second, as the temperature decreases, the movement of gas molecules slows, further improving the vacuum level. During the heating process, an inert gas (such as nitrogen) is typically introduced for gas displacement. This is done to expel air and moisture trapped in the material's pores, which could affect the cylinder's performance and hydrogen purity.

[0076] The viscosity of Examples 1-7 at 30°C ranged from 46.3 to 57.2 Pa·s, indicating that the resin system has a relatively high viscosity at room temperature. This relatively high viscosity allows the resin system to maintain good viscosity at room temperature without being too dry.

[0077] The viscosities of Examples 1-7 at 100°C ranged from 0.12 to 0.23 Pa·s, demonstrating the good fluidity of the resin system at high temperatures. This moderate high-temperature viscosity ensures uniform distribution of the resin system during curing while maintaining a certain viscosity.

[0078] In summary, the resin system of the embodiment of the present application shows a good balance in key process performance indicators such as gel time, curing time, glass transition temperature and viscosity. The comprehensive optimization of these properties enables the resin system to quickly form a certain shape during processing while maintaining appropriate viscosity to avoid premature curing or over-drying. This "sticky but not dry hand" feature not only improves the convenience of operation, but also ensures that the resin system can be evenly distributed during the curing process to form a high-quality composite material. Therefore, the resin system of the embodiment of the present application can effectively meet the preparation requirements of high-performance composite materials such as low-temperature and high-pressure hydrogen storage cylinders.

[0079] The mechanical properties of the resin systems prepared in Examples 1-7 and Comparative Examples 1-7 were evaluated using standard methods. The performance statistics of the resin systems are shown in Table 2: Table 2 Mechanical properties evaluation results of resin system As shown in Table 2, a comparison between Example 1 and Comparative Examples 1-3 shows that Example 1 exhibits significantly higher tensile strength, elongation at break, and fracture toughness at room temperature than Comparative Examples 1-3, demonstrating its superior strength and toughness at room temperature. The tensile strength, elongation at break, and fracture toughness of Example 1 at 90K are also significantly higher than those of Comparative Examples 1-3, demonstrating its ability to maintain high strength and toughness even at low temperatures. This is due to the inclusion of composite toughening agents (such as the polyether block polymer L-61 and SiO2 / PU core-shell particles) in Example 1. These composite toughening agents effectively absorb impact energy and slow crack propagation at low temperatures, significantly improving the low-temperature toughness and fracture toughness of the resin system. Nanoparticles (such as SiO2 / PU core-shell particles) deflect or blunt cracks, preventing them from propagating, further enhancing the crack resistance of the resin system. However, the omission of the composite toughening agent in Comparative Example 1, the nanoparticles in Comparative Example 2, and the flexible polymer in Comparative Example 3 significantly reduces the resin system's performance at low temperatures.

[0080] A comparison of Example 2 and Comparative Examples 4-5 shows that Example 2 exhibits significantly higher tensile strength, elongation at break, and fracture toughness at room temperature than Comparative Examples 4-5, indicating that it possesses higher strength and toughness at room temperature. The tensile strength, elongation at break, and fracture toughness of Example 2 at 90K are also significantly higher than those of Comparative Examples 4-5, demonstrating that it can maintain high strength and toughness even in low-temperature environments. This is because the ratio of flexible polymer to nanoparticles in Comparative Example 4 is improperly adjusted, and excessive use of the composite toughening agent can lead to a decrease in the performance of the resin system, particularly in terms of tensile strength. The SiO2 / PMMA core-shell particles in Comparative Example 5 have a high specific surface area and surface energy. Excessive use of these particles can significantly increase the viscosity of the resin system. This is because the nanoparticles form a network structure when dispersed in the resin, restricting the flow of resin molecules. This can also lead to enhanced interactions between the SiO2 / PMMA core-shell particles, making them more susceptible to agglomeration. The agglomerated SiO2 / PMMA core-shell particles will form larger particles, which are difficult to disperse evenly in the resin. Furthermore, the agglomerated SiO2 / PMMA core-shell particles will form stress concentration points, reducing the toughness and strength of the resin system.

[0081] From the comparison of Example 1 and Comparative Example 6, it can be seen that the tensile strength, elongation at break and fracture toughness of Example 1 at room temperature are significantly higher than those of Comparative Example 6, indicating that it has higher strength and toughness at room temperature. The tensile strength, elongation at break and fracture toughness of Example 1 at 90K are also significantly higher than those of Comparative Example 6, indicating that it can still maintain higher strength and toughness under low temperature conditions. This is because Comparative Example 6 adopts components such as tetrakis (2-hydroxyethyl) adipamide, tetramethylammonium hydroxide and polyetheramine. Although both tetrakis (2-hydroxyethyl) adipamide and polyetheramine can react with epoxy groups, the introduction of polyetheramine can reduce the cross-linked network density formed by the system, thereby weakening the mechanical strength and fracture toughness of the material. In addition, Comparative Example 6 only improves toughness by adding a higher proportion of polyetheramine, which can cause excessive flexible segments to reduce the cross-linking strength of the material, thereby causing the Tg of the material to decline, affecting the performance of the material at high temperatures.

[0082] A comparison of Example 4 and Comparative Example 7 shows that Example 4 exhibits significantly higher tensile strength, elongation at break, and fracture toughness at room temperature than Comparative Example 7, demonstrating its superior strength and toughness at room temperature. The tensile strength, elongation at break, and fracture toughness of Example 4 at 90K are also significantly higher than those of Comparative Example 7, demonstrating its ability to maintain high strength and toughness even at low temperatures. This is because Comparative Example 7 uses a different formulation (e.g., YD128, dicyandiamide, UR500, and polyetheramine). While the combination of YD128 and dicyandiamide provides a high crosslink density, the resin and curing agent are not composited, resulting in a lack of synergistic effects between the two systems. Furthermore, the high proportion of polyetheramine in the system, while contributing to improved material toughness, weakens the resin's strength, thus failing to meet the comprehensive performance requirements of low-temperature, high-pressure vessels, including strength, toughness, and heat resistance.

[0083] See also Figure 1 , Figure 1 The temperature-viscosity relationship curve of the resin system prepared in Example 1 and Comparative Example 8 is shown in FIG. Figure 1 (a) shows the temperature-viscosity relationship curve of the resin system in Example 1. It can be seen that at 25°C, the viscosity of the dry-process resin system in Example 1 is as high as 72,308 mPa·s, indicating that the resin system has high molecular chain entanglement density and structural integrity at room temperature. As the temperature increases, the viscosity decreases significantly, dropping to 477 mPa·s at 100°C. This indicates that the dry-process resin system has good fluidity during heating, which facilitates impregnation and distribution during the winding process. The high viscosity helps enhance the resin's coating of the fiber, thereby improving the mechanical properties and dimensional stability of the composite material. It also reduces the problems of uneven resin distribution and environmental pollution caused by excessive flow, making it suitable for the efficient preparation of high-performance composite materials.

[0084] from Figure 1 (b) shows the temperature-viscosity curve for the resin system of Comparative Example 8. At 25°C, the viscosity of the wet-process resin system of Comparative Example 8 is 982 mPa·s, significantly lower than that of the dry-process resin system of Example 1, indicating relatively low molecular chain entanglement density and structural integrity. Similarly, the viscosity decreases significantly with increasing temperature, reaching 102 mPa·s at 100°C. The wet-process resin system of Comparative Example 8 also exhibits good flowability during heating. Despite its lower viscosity, the wet-process resin system of Comparative Example 8 may require more control during the winding process to ensure uniform resin distribution and impregnation.

[0085] Therefore, the dry resin system provided in the embodiment of the present application can exhibit excellent processing characteristics during the winding molding process. At 25°C, it exhibits the characteristics of "sticky but not sticky", which means that the resin system does not produce excessive adhesion while maintaining a certain viscosity, thereby maintaining good operability and molding stability under high-speed winding conditions (speed of 100 to 200 meters / minute). In addition, after a short curing treatment of heating at 100°C for 1 hour, 120°C for 1 hour, and 130°C for 1 hour, the resin system can be cross-linked and cured to form the final product. This process is not only efficient and energy-efficient, but also very suitable for large-scale production applications, showing its significant advantages in industrial production.

[0086] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0087] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

[0088] Although the embodiments of the present application have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A resin system, characterized in that The resin system comprises the following components in parts by weight: 100 parts of a composite resin matrix, 25-60 parts of a composite curing agent, 1-2 parts of an accelerator, and 2-20 parts of a composite toughening agent; The composite toughening agent is obtained by mixing a flexible polymer and nanoparticles in a ratio of 1-20 parts by weight to 1-10 parts by weight; the flexible polymer is selected from at least one of polyether block polymer L-61, polyetheramine, and polyamide, and the molecular weight of the flexible polymer is greater than 1500; the nanoparticles are selected from at least one of silica, graphene, SiO2 / PU core-shell particles, and SiO2 / PMMA core-shell particles.

2. The resin system according to claim 1, characterized in that The composite resin matrix is obtained by mixing resin A and resin B in a ratio of 70-90 parts by weight to 10-30 parts by weight; The resin A is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and liquid phenolic resin; The resin B is selected from at least one of alicyclic epoxy resin and flexible side chain epoxy resin.

3. The resin system according to claim 2, characterized in that The bisphenol A epoxy resin is selected from at least one of E51 epoxy resin, E44 epoxy resin, and E42 epoxy resin; The bisphenol F epoxy resin is selected from at least one of YDF-161H epoxy resin and YDF-170 epoxy resin; The liquid phenolic resin is selected from at least one of F-51 phenolic resin and F-44 phenolic resin; The alicyclic epoxy resin is selected from at least one of EHPE-3150 resin, bis(7-oxabicyclo[4.1.0]3-heptylmethyl)adipate, and 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate; The flexible side chain epoxy resin is allyl glycidyl ether.

4. The resin system according to claim 1, characterized in that The composite curing agent is obtained by mixing curing agent A and curing agent B according to a weight ratio of 5-30:12-40; The curing agent A is a latent amine curing agent; Wherein, the latent amine curing agent is selected from at least one of dicyandiamide, isophoronediamine, 1,2-cyclohexanediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, and m-phenylenediamine; The curing agent B is an acid anhydride curing agent; Wherein, the acid anhydride curing agent is selected from at least one of methyl nadic anhydride, phthalic anhydride and hexahydrophthalic anhydride.

5. The resin system according to claim 1, characterized in that The accelerator is selected from at least one of organic urea accelerators, tertiary amine accelerators, and boron amine complexes; wherein, The organic urea accelerator is selected from at least one of UR200, UR300, and UR500; The tertiary amine accelerator is selected from at least one of DMP-30 and BDMA.

6. The method for preparing the resin system according to any one of claims 1 to 5, characterized in that: The resin system preparation method comprises: Mixing resin A and resin B, heating to 60-100° C. and mixing at a speed of 200-1000 rpm for 10-20 minutes to obtain a composite resin matrix; Mix curing agent A and curing agent B, heat to 40-80°C and mix at a speed of 500-800 rpm for 15-20 minutes to obtain a composite curing agent; The flexible polymer and the nanoparticles are mixed, heated to 80-160° C., and mixed at a rotation speed of 1500-2000 rpm for 10-20 minutes to obtain a composite toughening agent; The composite resin matrix, the composite curing agent, the composite toughening agent and the accelerator are mixed, heated to 60-100° C. and mixed for 20-30 minutes, and then ultrasonically dispersed and vacuum defoamed to obtain a resin system.

7. A method for preparing a prepreg, characterized in that: The prepreg preparation method comprises: Add the resin system to the dipping tank and heat it to 50°C, then evenly spread the heated resin system on the release paper and fully impregnate it with the reinforcing fiber to obtain a prepreg; wherein the resin system is the resin system according to any one of claims 1 to 5 or the resin system prepared by the resin system preparation method according to claim 6; A release paper is laid flat on the surface of the prepreg, the prepreg is pre-cured, and then cooled. After cooling, the release paper on the surface is peeled off, a polyethylene film is laid on the surface, and the prepreg is rolled up to obtain the prepreg.

8. The method for preparing prepreg according to claim 7, wherein: The pre-curing temperature is 120° C., the heating time is 20-30 minutes, and the prepreg obtained by winding is placed at room temperature for at least 60 days.

9. An application of a prepreg, characterized in that: The prepreg prepared by the prepreg preparation method according to any one of claims 7-8 is used in low-temperature and high-pressure hydrogen storage cylinders.

10. The use according to claim 9, characterized in that The prepreg is cured by heating and then cooled to obtain a low-temperature and high-pressure hydrogen storage cylinder; The conditions for the temperature-raising curing are: 100°C / 1h+120°C / 1h+130°C / 1h.

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