关键词: 聚酰亚胺纤维, 环氧树脂, 硅烷偶联剂, 表面改性, 耐磨性能

Abstract:

Objective Polyimide (PI) fibers are widely used in aerospace, military protection, and other special fields due to their excellent high temperature resistance, mechanical strength, and chemical stability. However, its shortcomings such as smooth surface and insufficient abrasion resistance limit its long-term performance in extreme environments. In order to improve the surface wear resistance of PI fiber materials and enhance their applicability in special environments such as high temperature and high friction, the present study innovatively adopts the method of grafting epoxy resin with silane coupling agent to functionalize the surface of PI fibers, with a view to significantly improving their surface wear resistance characteristics while maintaining their original excellent properties.

Method The surface of PI fibers was hyperbranched by the chemical modification scheme of silane coupling agent (3-isocyanatopropyltrimethoxysilane, IPTMS) grafted with epoxy resin (EP), and hyperbranched-modified epoxy resin-polymide(HPS-EA-PI) fibers with high surface roughness and excellent abrasion-resistant properties were prepared. The effects of alkaline treatment concentration and treatment time on fiber surface activity were systematically investigated, and the concentration gradient of IPTMS modifier was optimized. The chemical structure, surface morphology and roughness of the fibers before and after modification were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy. The mechanical properties, thermal stability and wear resistance were evaluated by universal material testing machine, thermogravimetric analyzer and friction and wear testing machine, respectively.

Results Surface activation treatment results were analysed. When treated with 4 mol/L NaOH solution for 5 min, the carboxyl group content on the fiber surface increased significantly, providing an ideal active site for the subsequent silane coupling agent grafting. Roughness evolution analysis revealed that with the increase of IPTMS concentration for 0%, 25%, 50%, 75% and 100%, the roughness of the modified fibers was enhanced by 104%, and SEM showed that the coating was successfully applied on the fiber surface. HPS-EA-PI fibers prepared under the optimal process (75% IPTMS) maintained the original mechanical properties and thermal stability while the abrasion resistance was improved by 190% compared with the unmodified sample. XPS confirmed the formation of Si—O—C bonds, indicating that the epoxy resin formed a solid chemical bond with the PI fibers via silane coupling agent, which was the key factor for the performance enhancement.

Conclusion The epoxy resin/silane coupling agent hyperbranching modification technology developed in this study successfully optimized the synergistic "strength-toughness-wear resistance" of PI fibers by precisely regulating the chemical composition and microscopic morphology of the fiber surface. The prepared HPS-EA-PI fibers show significantly better service performance than traditional PI fibers in extreme environments, and their surface modification strategy provides a new idea for the functional design of high-performance polymer fibers, which has an important application prospect in the fields of spacecraft thermal protection system and special protective clothing. It is suggested that follow-up studies should focus on the long-term durability performance of the modified fibers under simulated real-world working conditions.

Key words: polyimide fiber, epoxy resin, silane coupling agent, surface modification, wear resistance