Preparation method and application of wear-resistant polyimide material

Abstract

The invention provides a preparation method and application of a wear-resistant polyimide material, and the preparation method comprises the following steps: S1, adding a polyimide material into an alkali solution for reaction, cleaning reactants with acid and ethanol, and drying to obtain an activated polyimide material; s2, adding the activated polyimide material into a silane coupling agent solution for reaction, cleaning reactants with ethanol and water, and drying to obtain a modified polyimide material with silicon-oxygen bond active sites on the surface; s3, adding the modified polyimide material with silicon-oxygen bond active sites on the surface into a modified epoxy resin solution, adjusting the pH value to be acidic, and reacting to obtain the wear-resistant modified polyimide material, wherein the modified epoxy resin solution is obtained by reacting a silane coupling agent with acrylate. According to the method, the wear resistance of the polyimide can be improved on the premise that other properties of the polyimide material are not influenced.

Description

Technical Field

[0001] This invention relates to the field of new materials, and in particular to a method for preparing and applying a wear-resistant polyimide material. Background Technology

[0002] Polyimide is a class of high-performance polymer materials characterized by imide rings. Due to its excellent mechanical properties, resistance to high and low temperatures, low dielectric, high insulation, high flame retardancy, and radiation resistance, it has broad application prospects in aerospace, aviation, safety protection, nuclear industry and other fields.

[0003] However, in practical applications, the abrasion resistance defects of polyimide materials have become a key bottleneck restricting their further expansion into various application scenarios. Currently, industrially produced high-strength, high-modulus polyimide materials generally employ a surface-sizing-free process to avoid interference from the sizing agent in subsequent composite processes, resulting in a lack of effective protection for the fiber surface. Simultaneously, the highly ordered aromatic structure of the polyimide molecular chain results in extremely low surface energy and strong chemical inertness. These two characteristics combined make it difficult for its abrasion resistance to meet the requirements of repeated stretching, bending, and torsion in weaving and applications. Furthermore, due to the smooth fiber surface and poor surface wettability, it is easily damaged because a stable interfacial phase cannot be formed between the fiber and the reinforcing material, leading to poor adhesion between the fiber and the reinforcing material when used as a matrix.

[0004] To address the issues of surface inertness and insufficient wear resistance in polyimide materials, researchers have conducted extensive studies. However, existing technologies still have significant limitations. Current research on polyimide material modification primarily focuses on molecular design and processing modification, lacking research on surface activity improvement. At the molecular design level, while introducing functional groups such as fluorine- or silicon-containing groups to adjust the molecular chain structure can improve surface properties to some extent, the synthesis process is complex, the reaction conditions are harsh, and it disrupts the original regularity of the polyimide molecular chain, leading to a 15%-20% decrease in mechanical properties and a significant reduction in high and low temperature resistance, such as a 10-25°C decrease in glass transition temperature. At the processing modification level, wear-resistant particles are mainly introduced through blending and filling. However, the dispersion of these particles in the polyimide matrix is ​​difficult to control, leading to agglomeration. This not only fails to effectively improve wear resistance but also causes new problems such as deterioration of dielectric properties (dielectric constant increases by 0.3-0.8) and decreased processing fluidity.

[0005] Current methods for addressing the surface inertness of polyimide materials include alkaline etching pretreatment, high-energy X-ray treatment, plasma treatment, and molecular structure design. However, these existing technologies also have significant drawbacks: While alkaline etching pretreatment can introduce active groups such as carboxyl and hydroxyl groups onto the material surface through hydrolysis, the etching process is difficult to control precisely, easily leading to excessive corrosion of the material surface, forming irregular holes and cracks, reducing tensile strength by 20%-30%, and the impurities generated by etching are difficult to completely remove, affecting the stability of subsequent composite processes; although high-energy X-ray treatment and plasma treatment can rapidly improve surface activity, the high energy can break the chemical bonds of the polyimide molecular chain, leading to cross-linking or degradation of the material, and significantly reducing its resistance to high and low temperatures; molecular structure design optimization faces problems such as high synthesis costs and poor process compatibility, making it difficult to achieve large-scale industrial applications.

[0006] In summary, existing polyimide material modification technologies often sacrifice key properties such as the original mechanical properties, high and low temperature resistance, and dielectric properties of the material while improving surface properties or wear resistance. A mature technical solution has not yet been formed that can effectively improve the wear resistance of polyimide without damaging its core properties. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing and applying wear-resistant polyimide materials. By modifying the polyimide material and preparing a coating, the wear resistance of the polyimide is improved without affecting other properties of the polyimide material, thereby extending the service life of the polyimide material in harsh space environments.

[0008] To achieve the above objectives, this technical solution provides a method for preparing a wear-resistant polyimide material, comprising the following steps: S1: Add polyimide material to an alkaline solution to react, wash the reactants with acid and ethanol, and then dry to obtain activated polyimide material; S2: The activated polyimide material is added to the silane coupling agent solution for reaction. The reactants are washed with ethanol and water and then dried to obtain the modified polyimide material with active sites of silicon-oxygen bonds on the surface. S3: Modified polyimide material with active sites of silicon-oxygen bonds on its surface is added to modified epoxy resin solution and the pH is adjusted to acidic reaction. The reactants are washed with alcohol and water and then dried to obtain wear-resistant modified polyimide material. The modified epoxy resin solution contains silane coupling agent and modified epoxy resin.

[0009] This method involves treating activated polyimide materials with silane coupling agent solutions to obtain modified polyimide materials with active siloxane bond sites on their surface. Active sites are introduced through surface activation of the polyimide, and chemical bridging is constructed using silane coupling agents. Subsequently, the modified polyimide materials with active siloxane bond sites are immersed in a modified epoxy resin solution. The siloxane bonds in the silane-modified epoxy resin of the modified epoxy resin solution undergo a hydrolytic polymerization reaction with the siloxane bonds on the surface of the modified polyimide materials, forming a hyperbranched structure. This structure exists in a more compact form on the surface of the polyimide material, resulting in a hyperbranched modified polyimide material with enhanced wear resistance. This modification method significantly improves the wear resistance of polyimide without compromising its core properties.

[0010] In step S1 of this scheme, the surface of the polyimide material after ultrasonic cleaning is treated with alkali to selectively hydrolyze the imine rings on the surface of the polyimide material with alkali solution to introduce active groups.

[0011] In some embodiments, the ultrasonically cleaned polyimide material is added to a 1-10 mol / L sodium hydroxide solution and reacted at 20-80°C for 2-60 minutes.

[0012] In some embodiments, the reactants are washed with 0.1 mol / L dilute hydrochloric acid and anhydrous ethanol and then dried at 75-85°C for 10-14 h to obtain activated polyimide material.

[0013] In some embodiments, the ultrasonically cleaned polyimide material is added to a 4.0 mol / L sodium hydroxide solution and reacted at 30°C for 5 min. The reactants are then cleaned with 0.1 mol / L dilute hydrochloric acid and anhydrous ethanol and dried at 80°C for 12 h to obtain activated polyimide material.

[0014] Step S2 of this scheme involves using the amino groups in the silane coupling agent to chemically bond with the carboxyl groups on the surface of the activated polyimide material, thereby grafting an active layer containing siloxane end groups onto the surface of the polyimide material to obtain a modified polyimide material with siloxane bond active sites on the surface.

[0015] In step S2, the activated polyimide material is added to the silane coupling agent solution and reacted at 30~100℃ for 1~10h. After washing the reactants with dilute hydrochloric acid and anhydrous ethanol, the reactants are dried at 50~100℃ for 3~30h to obtain the modified polyimide material with active sites of silicon-oxygen bonds on the surface.

[0016] Preferably, the activated polyimide material is added to a silane coupling agent solution and reacted at 55-65°C for 4-6 hours. After washing the reactants with 0.1 mol / L dilute hydrochloric acid and anhydrous ethanol, the reactants are dried at 75-85°C for 10-14 hours to obtain a modified polyimide material with active sites of silicon-oxygen bonds on its surface.

[0017] In some embodiments, the activated polyimide material is added to a 3-aminopropyltriethoxysilane solution and reacted at 60°C for 5 hours. After washing the reactants with anhydrous ethanol and water, the reactants are dried at 80°C for 12 hours to obtain a modified polyimide material with active sites on the surface of silicon-oxygen bonds.

[0018] In some embodiments, the silane coupling agent in the silane coupling agent solution is 3-isocyanopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0019] In step S3 of this scheme, the modified epoxy resin in the modified epoxy resin solution is prepared by a two-step reaction. First, esterification reaction is carried out between bisphenol A diglycidyl ether containing epoxy groups and acrylic acid containing unsaturated double bonds to obtain acrylate containing ester bonds and unsaturated double bonds. Then, the acrylate containing ester bonds and unsaturated double bonds is mixed with a silane coupling agent to carry out a hydrolysis condensation reaction to obtain modified epoxy resin containing silicon-oxygen bonds.

[0020] In some embodiments, a method for preparing modified epoxy resin includes: Bisphenol A diglycidyl ether and triphenyl were mixed and added to acrylic acid. The mixture was reacted at 50-100℃ for 1-10 h to obtain a transparent viscous liquid. The transparent viscous liquid was washed and separated to obtain purified acrylate. 0.01%-1% of silane coupling agent and 0.01%-1wt% of dibutyltin dilaurate were added to the acrylate. The mixture was reacted at 20-80℃ for 1-8 h. After the reaction was completed, the silane coupling agent, anhydrous ethanol, and distilled water were added to the above reactants and mixed evenly to obtain a modified epoxy resin solution.

[0021] Preferably, bisphenol A diglycidyl ether and triphenylphosphine are mixed and heated to 70°C in an inert gas environment. Acrylic acid is added dropwise and reacted at 80°C to obtain a transparent viscous liquid. The transparent viscous liquid is washed and separated to obtain purified acrylate.

[0022] In some embodiments, the volume ratio of silane coupling agent, anhydrous ethanol, and distilled water is 1~5: 2~12: 1~4.

[0023] In some embodiments, the silane coupling agent in the modified epoxy resin solution is selected from one or any combination of 3-(isobutenoyloxy)propyltrimethoxysilane (KH570), isobutyl(trimethoxy)silane (IBTMO), 1-[3-(trimethoxysilyl)propyl]urea (UTMS), (3-chloropropyl)trimethoxysilane (CPTMO), and 3-isocyanopropyltrimethoxysilane (IPTMS).

[0024] Preferably, the silane coupling agent is 3-isocyanopropyltrimethoxysilane.

[0025] Preferably, when the silane coupling agent is 3-isocyanopropyltrimethoxysilane, the content of the silane coupling agent is 0.1~0.3% of the activated polyimide material.

[0026] In some embodiments, the ratio of activated polyimide material, silane coupling agent and modified epoxy resin is 1~2g: 3~5mL: 5~8mL.

[0027] Furthermore, bisphenol A diglycidyl ether and triphenylphosphine were mixed and heated to 70°C in an inert gas atmosphere. Acrylic acid was added dropwise and the mixture was reacted at 80°C for 4 hours to obtain a transparent viscous liquid.

[0028] Furthermore, the transparent viscous liquid was washed five times with distilled water to separate unreacted acrylic acid (supernatant). Then, it was washed three times with a mixed solvent of acetone and cyclohexane to effectively remove the catalyst triphenylphosphine (TPP) and residual esterification byproducts. Finally, the purified product was transferred to a vacuum drying oven and dried at 30 °C for 8 hours to completely remove trace amounts of moisture and organic solvents, obtaining a high-purity acrylate (EA) product.

[0029] In some embodiments, acrylate and dibutyltin dilaurate are mixed and heated to 40°C in an inert gas environment. After adding a silane coupling agent, the mixture is reacted at 40°C for 3 hours to obtain a modified epoxy resin.

[0030] In some embodiments, a modified epoxy resin, anhydrous ethanol, and water are mixed to obtain a modified epoxy resin solution, wherein the modified epoxy resin solution is a pale blue, transparent, homogeneous liquid.

[0031] In step S3, the pH value is adjusted to 4-5 using hydrochloric acid, and the mixture is heated to 60°C for 5 hours. The acidic environment accelerates the hydrolysis of siloxane bonds, and the constant temperature of 60°C provides energy for the reaction. This allows the siloxane groups remaining on the surface of the polyimide from APTES to undergo hydrolysis and polymerization simultaneously with the siloxane groups in the modified epoxy resin. The siloxane groups first hydrolyze into silanol groups, which then further condense to form Si-O-Si bonds, ultimately forming a three-dimensional cross-linked hyperbranched structure on the surface of the polyimide.

[0032] Furthermore, the reactants were washed with anhydrous ethanol and water and then dried at 80 °C for 12 h to obtain wear-resistant modified polyimide material.

[0033] The wear-resistant modified polyimide material obtained by this method has a hyperbranched coating, which has two core functions: ① Physical barrier: The dense coating directly bears the mechanical stress during the friction process, preventing the polyimide body from being directly worn; ② Interface enhancement: The coating is tightly connected to the polyimide substrate through Si-OC bonds and amide bonds, and combined with the physical interlocking effect of the previous surface roughness improvement, it completely solves the problem of easy coating peeling off; At the same time, the silicon-oxygen bonds in the coating work synergistically with the epoxy resin chains to greatly enhance the wear resistance while retaining the original high and low temperature resistance and mechanical properties of polyimide.

[0034] Secondly, this solution provides an application of a method for preparing wear-resistant polyimide materials, thereby preparing wear-resistant polyimide materials with wear-resistant properties.

[0035] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects: This solution addresses the issues of insufficient surface inertness and wear resistance in polyimide materials, as well as the tendency of existing modification techniques to compromise their core properties. It proposes a method to improve the wear resistance of polyimide materials. First, the polyimide material is alkali-treated to activate the surface and introduce carboxyl groups. Then, an active transition layer containing silicon-oxygen bonds is constructed via APTES grafting. Simultaneously, high-purity EA is synthesized and reacted with a silane coupling agent to prepare a silane-modified epoxy resin solution. Finally, the APTES-treated polyimide material is immersed in this solution, and a hyperbranched wear-resistant coating is formed through pH adjustment and heating. Ultimately, while retaining the original mechanical properties and high / low temperature resistance of polyimide, its wear resistance is significantly improved. Furthermore, the process is controllable, the material has broad morphological compatibility, and it possesses potential for industrial application.

[0036] The excellent wear resistance of the wear-resistant polyimide material prepared by this method is attributed to: 1. Enhanced interfacial bonding due to the chemical bonds of the hyperbranched structure: The siloxane groups (Si-O-CH3) of the silane coupling agent undergo hydrolytic condensation with the carboxyl groups on the surface of the alkali-treated polyimide material to form stable Si-OC bonds. Simultaneously, its organic ends (isocyanate groups) react with the epoxy resin to form a chemical cross-linking network. This chemical bonding significantly improves the interfacial bonding strength between the coating and the fiber, avoiding the problem of easy detachment of the physically adsorbed coating, thereby enhancing wear resistance. 2. Physical barrier effect of the uniform coating: The silane coupling agent promotes the formation of a uniform and dense coating between the polysiloxane and epoxy resin, completely covering the fiber surface (SEM and AFM results show that the surface roughness increased from 199 nm to 391 nm). This coating acts as a physical barrier, directly bearing the mechanical stress during friction and reducing the direct wear of the polyimide fiber itself. 3. Synergistic effect of coating structure and wear resistance: The wear-resistant polyimide material formed by this solution has a uniform coating with moderate roughness, increasing the wear resistance by 190%. 4. Balance between thermal stability and mechanical properties: TGA shows that the coating slowly decomposes at high temperatures, but the thermal stability of the polyimide matrix is ​​not significantly compromised. The silane coupling agent constructs a high-strength, uniform, and dense wear-resistant coating on the polyimide fiber surface through a dual mechanism of chemical bonding and physical coverage. Its optimized roughness and interface structure effectively disperse frictional stress, reduce fiber wear, and ultimately significantly improve wear resistance (190%), while maintaining the mechanical and thermal stability of the polyimide fiber. Attached Figure Description

[0037] Figure 1 These are infrared spectra of polyimide fibers coated with different silane coupling agents.

[0038] Figure 2 These are infrared spectra of polyimide fibers modified with different concentrations of silane coupling agents.

[0039] Figure 3 These are XPS spectra of polyimide fibers modified with different concentrations of silane coupling agents.

[0040] Figure 4 The images show the SEM morphology of polyimide fibers modified with different concentrations of silane coupling agent.

[0041] Figure 5 The AFM morphology of polyimide fibers modified with different concentrations of silane coupling agent is shown.

[0042] Figure 6 The surface roughness of polyimide fibers modified with different concentrations of silane coupling agent varies.

[0043] Figure 7 The average abrasion resistance curves of polyimide fiber surfaces modified with different concentrations of silane coupling agent are shown. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0045] Example 1 Ultrasonic-cleaned polyimide fibers were placed in a 4.0 mol / L sodium hydroxide (NaOH) solution and reacted at 30 °C for 5 min. After rinsing repeatedly with dilute 0.1 mol / L HCl and anhydrous ethanol, the fibers were dried in an oven at 80 °C for 12 h. Next, the fibers were placed in a 3-aminopropyltriethoxysilane (APTES) solution and reacted at 60 °C for 5 h. After rinsing repeatedly with anhydrous ethanol and distilled water, the fibers were dried in an oven at 80 °C for 12 h. 0.029 mol of bisphenol A diglycidyl ether and 0.2 g of triphenylphosphine (TPP) were added to a four-necked round-bottom flask and stirred thoroughly for 30 min. The temperature was then slowly raised to 70 °C under nitrogen atmosphere. 4 mL of acrylic acid was added dropwise, and the reaction was continued at 80 °C for 4 hours, at which point the system gradually transformed into a transparent, viscous liquid. After the reaction was completely terminated, the product was washed five times with distilled water to separate unreacted acrylic acid (supernatant). Then, a three-stage gradient washing process was performed using a mixed solvent of acetone and cyclohexane to effectively remove the triphenylphosphine (TPP) catalyst and residual esterification byproducts. Finally, the purified product was transferred to a vacuum drying oven and dried at 30 °C for 8 hours to completely remove trace amounts of moisture and organic solvents, yielding a high-purity acrylate (EA) product. EA and a small amount of dibutyltin dilaurate (DBTDL) catalyst were added to a reaction flask. Under a nitrogen atmosphere, the temperature was slowly raised to 40 °C. Different silane coupling agents were then added dropwise to the well-stirred reaction mixture, and the mixture was maintained at 40 °C for 3 hours. After the reaction was complete, anhydrous ethanol and distilled water were added to the above reactants at a volume ratio of 1:5:2.2 (coupling agent: anhydrous ethanol: distilled water) and mixed thoroughly to obtain a pale blue, transparent, homogeneous liquid. APTES-treated polyimide fibers were placed in the above mixed solution, and hydrochloric acid was added dropwise until the pH value reached 4-5. The reactor was heated to 60 °C and maintained for 5 h. The fibers were then removed and washed continuously with anhydrous ethanol and distilled water, and dried at 80 °C for 12 h to obtain modified fibers.

[0046] Based on the different functional groups contained in the silane coupling agents, Example 1 compares the structural changes of polyimide materials before and after modification by several silane coupling agents at the same concentration. The silane coupling agents include 3-(isobutenoyloxy)propyltrimethoxysilane (KH570), isobutyl(trimethoxy)silane (IBTMO), 1-[3-(trimethoxysilyl)propyl]urea (UTMS), (3-chloropropyl)trimethoxysilane (CPTMO), and 3-isocyanopropyltrimethoxysilane (IPTMS). The infrared spectra of polyimide materials modified with 50% molar ratios of different silane coupling agents are shown below. Figure 1 As shown in the figure, except for 1773, 1360 and 820 cm -1 The characteristic absorption peak of the nearby imide group is at 1095 cm⁻¹. -1 A strong absorption peak appeared, which is caused by the antisymmetric stretching vibration of the Si-O-Si bond, at 690 cm⁻¹. -1 The absorption peaks around 460 cm⁻¹ are absorption peaks of the symmetric stretching vibration of the Si-C bond. -1 The absorption peaks that appear on the left and right are caused by the bending vibration of the Si-O bond.

[0047] In summary, 3-isocyanopropyltrimethoxysilane (IPTMS) is the most suitable coupling agent for the preparation of the coating in this study among several coupling agents. Therefore, subsequent experiments will mainly focus on the effect of IPTMS concentration changes on the properties of polyimide fibers.

[0048] Example 2 This section describes the modified fiber samples prepared using 3-isocyanopropyltrimethoxysilane (IPTMS) at molar concentrations ranging from 0%, 25%, 75%, to 100%, denoted as HPS-EA-polyimide #0, HPS-EA-polyimide #1, HPS-EA-polyimide #2, HPS-EA-polyimide #3, and HPS-EA-polyimide #4. The unmodified polyimide fiber is denoted as polyimide #0. The infrared spectra of polyimide fibers modified with different concentrations of IPTMS are shown below. Figure 2 As shown, with the increase of IPTMS concentration, except for 1773, 1360, and 820 cm⁻¹, [the concentrations]... -1 The characteristic absorption peak of the nearby imide group is at 1095 cm⁻¹. -1 A strong absorption peak appeared, which is caused by the antisymmetric stretching vibration of the Si-O-Si bond, at 690 cm⁻¹. -1 The absorption peaks around 460 cm⁻¹ are absorption peaks of the symmetric stretching vibration of the Si-C bond. -1The absorption peaks appearing on the left and right sides are caused by the bending vibrations of the Si-O bonds. Therefore, combined with FTIR spectrum analysis, the modified polyimide fibers have, to some extent, coated a novel wear-resistant layer. Furthermore, the intensity of the absorption peaks shows that these newly appearing characteristic peaks gradually increase with the increase of the 3-isocyanopropyltrimethoxysilane (IPTMS) content, with the most pronounced peak observed in HPS-EA-polyimide #3 fiber.

[0049] Quantitative analysis of the surface chemical state of modified grafted polyimide fibers was performed using XPS, and the results are as follows: Figure 3 As shown, the changes in surface elemental composition reveal a significant increase in oxygen content and a decrease in carbon content after modification. Simultaneously, a characteristic silicon signal was detected, directly confirming the successful grafting of polysiloxane onto the fiber surface. This evolution in elemental proportions is attributed to the introduction of abundant functional groups such as CO (epoxy resin), C=O (carboxylic acid derivative), and Si-O-Si (characteristic polysiloxane bonds) in the grafted layer. Peak segmentation of the C1s spectrum revealed four characteristic peaks: 284.7 eV corresponding to CH bonds, 285.4 eV corresponding to CN bonds, 286.4 eV representing CO bonds, and 288.7 eV representing C=O bonds. Notably, the Si2p spectrum exhibits a distinct peak shape at 102.5 eV, with its binding energy position closely matching the standard values ​​for Si-O-Si bonds (102.3-103.1 eV), further demonstrating the feasibility of HPS-EA modified polyimide fibers.

[0050] Example 3 Modification with 3-isocyanopropyltrimethoxysilane (IPTMS) also alters the surface morphology of polyimide fibers. SEM was used to visually analyze the surface morphology and appearance of the modified polyimide fiber samples. Figure 4 (a) is polyimide #0 with a smooth surface; Figure 4 (b) shows the surface of HPS-EA-polyimide #0 fiber, where discretely distributed nanoparticles appear on the fiber surface, forming an "island-like" deposition structure, which improves the surface roughness. Figure 4 (c) shows the surface of HPS-EA-polyimide #1 fiber, where the particle density is significantly increased and local agglomeration occurs, but a continuous covering layer is not formed, exposing part of the substrate area; further increasing the concentration to HPS-EA-polyimide #2 ( Figure 4 In (d), the particles aggregate into a semi-continuous film layer, which improves the coverage, but micron-sized pore defects still exist in some areas; Figure 4 (e) in the image represents the surface of HPS-EA-polyimide #3 fiber, where coating particles form a dense and uniform three-dimensional network coating through interfacial condensation; however, see... Figure 4In (f), excessive modification of HPS-EA-polyimide #4 resulted in an excessively thick coating, leading to microcracks and particle accumulation on the surface, with the roughness increasing to 439 nm. This structural heterogeneity may cause stress concentration, resulting in a decrease in interfacial bonding strength. Therefore, the preparation conditions for HPS-EA-polyimide #3 fibers represent the optimal concentration conditions for fiber modification treatment.

[0051] The surface roughness of the deposited layer formed by the coating on the fiber surface was observed by characterizing the polyimide fiber surface with AFM at different IPTMS concentrations. This observation provides another perspective on the accuracy of the required modification conditions. The results are as follows: Figure 5 and Figure 6 As shown, with the increase of IPTMS concentration, coating particles gradually form a coating layer on the surface of polyimide fibers, and the surface roughness of the fibers also increases. Figure 5 As can be seen in (e), a uniform and complete coating has been formed, while Figure 5 In (f), the coated particles have already accumulated on the fiber surface, disrupting the smoothness of the coating surface. Secondly, it can be seen that the surface roughness increases non-linearly with increasing IPTMS concentration: 199 nm at 0%, reaching an optimal value of 391 nm at 75% concentration, and increasing to 439 nm at 100% concentration. Therefore, coating treatment of HPS-EA-polyimide #3 fibers represents the optimal treatment conditions.

[0052] Example 5 The abrasion resistance of polyimide fibers modified with IPTMS at different concentrations was quantitatively characterized using an LFY-109T abrasion tester. Figure 7 Cyclic friction test data showed that the friction cycle life of polyimide #0 was 2,104 cycles, while the samples treated with gradient concentrations of silane exhibited a nonlinear change pattern of initial optimization followed by degradation. Among them, the friction durability of HPS-EA-polyimide #3 was significantly improved to 6,095 cycles, achieving approximately 190% improvement in wear resistance compared to the original sample. Microscopic morphology analysis confirmed that moderate concentration of IPTMS modification effectively enhanced the fiber-resin interfacial bonding strength. AFM and SEM characterization showed that a continuous and dense organic-inorganic hybrid protective layer was formed on the material surface, and this structure significantly improved the energy dissipation capacity during friction.

[0053] Notably, when the IPTMS concentration exceeded the critical value (HPS-EA-polyimide #4), the number of friction cycles plummeted to 4004. In-depth analysis of the failure mechanism revealed that excessive siloxane precursors induced phase separation in the coating's microstructure. SEM images showed obvious disordered accumulation of nanoscale aggregates, and surface characterization revealed an abnormally increased roughness. This multi-scale structural defect exacerbated stress concentration during friction, accelerating the initiation and propagation of microcracks, ultimately leading to early fiber fracture failure.

[0054] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a wear-resistant polyimide material, characterized in that, Includes the following steps: S1: Add polyimide material to an alkaline solution to react, wash the reactants with acid and ethanol, and then dry to obtain activated polyimide material; S2: The activated polyimide material is added to the silane coupling agent solution for reaction. The reactants are washed with ethanol and water and then dried to obtain the modified polyimide material with active sites of silicon-oxygen bonds on the surface. S3: Modified polyimide material with active sites of silicon-oxygen bonds on its surface is added to modified epoxy resin solution and the pH is adjusted to acidic reaction. The reactants are washed with alcohol and water and then dried to obtain wear-resistant modified polyimide material. The modified epoxy resin solution contains silane coupling agent and modified epoxy resin.

2. The method for preparing the wear-resistant polyimide material according to claim 1, characterized in that, The ultrasonically cleaned polyimide material is added to a 1-10 mol / L sodium hydroxide solution and reacted at 20-80℃ for 2-60 minutes.

3. The method for preparing the wear-resistant polyimide material according to claim 1, characterized in that, The activated polyimide material was added to a silane coupling agent solution and reacted at 30-100°C for 1-10 hours. After washing the reactants with dilute hydrochloric acid and anhydrous ethanol, the reactants were dried at 50-100°C for 3-30 hours to obtain a modified polyimide material with active sites of silicon-oxygen bonds on its surface.

4. The method for preparing the wear-resistant polyimide material according to claim 1, characterized in that, Bisphenol A diglycidyl ether and triphenyl were mixed and added to acrylic acid. The mixture was reacted at 50-100℃ for 1-10 h to obtain a transparent viscous liquid. The transparent viscous liquid was washed and separated to obtain purified acrylate. 0.01%-1% of silane coupling agent and 0.01%-1wt% of dibutyltin dilaurate were added to the acrylate. The mixture was reacted at 20-80℃ for 1-8 h. After the reaction was completed, the silane coupling agent, anhydrous ethanol, and distilled water were added to the above reactants and mixed evenly to obtain a modified epoxy resin solution.

5. The method for preparing the wear-resistant polyimide material according to claim 5, characterized in that, The volume ratio of silane coupling agent, anhydrous ethanol, and distilled water is 1~5: 2~12: 1~4.

6. The method for preparing the wear-resistant polyimide material according to claim 1, characterized in that, The ratio of activated polyimide material, silane coupling agent and modified epoxy resin is 1~2 g: 3~5 mL: 5~8 mL.

7. The method for preparing the wear-resistant polyimide material according to claim 1, characterized in that, The silane coupling agent in the modified epoxy resin solution is selected from one or any combination of 3-(isobutenoyloxy)propyltrimethoxysilane, isobutyl(trimethoxy)silane, 1-[3-(trimethoxysilyl)propyl]urea, (3-chloropropyl)trimethoxysilane and 3-isocyanopropyltrimethoxysilane.

8. The method for preparing the wear-resistant polyimide material according to claim 1, characterized in that, The silane coupling agent in the silane coupling agent solution is 3-isocyanopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

9. The method for preparing the wear-resistant polyimide material according to any one of claims 1 to 8, characterized in that, It is used to prepare wear-resistant polyimide materials, wherein the surface of the wear-resistant polyimide material has a hyperbranched structure.

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