Abstract:

Significance As a critical strategic material for aerospace, personal protection, and other cutting-edge applications, structural failures in para-aramid products could trigger significant safety hazards and economic risks. Given the escalating operational demands on the comprehensive performance of para-aramid fibers in practical applications, transcending conventional processing limitations to achieve autonomous production of high-modulus para-aramid fibers has emerged as a pivotal challenge in advanced fiber technology sector. This study conducts in-depth analysis of the structure-property relationships between multiscale structural configurations and macroscopic performance, while systematically reviewing the developmental trajectory of high-modulus para-aramid preparation technologies. The review aims to establish theoretical foundations for optimizing heat treatment processes and developing novel modification approaches, thereby addressing industrial technical bottlenecks and enhancing the competitiveness of domestically produced high-modulus para-aramid fibers in premium application sectors. +++Progress The heat treatment process of para-aramid fibers involves synergistic control of temperature, tension, and time to rapidly remove internal moisture while strengthening hydrogen bonding between molecular chains, thereby significantly improving fiber modulus. However, this process relies on high-temperature and high-tension conditions, which not only increase the risk of molecular chain breakage but also impose stringent requirements on equipment precision and stability. In order to further enhance the modulus of para-aramid fibers, researchers have proposed various modification strategies centered on molecular structure design and processing innovations, each with distinct advantages yet facing practical challenges. In the field of spinning dope modification, the use of high-molecular-weight para-aramid resin effectively broadens the liquid crystal phase temperature range, enabling highly ordered molecular chain alignment and laying the foundation for constructing high-crystallinity, high-modulus para-aramid fibers. However, challenges arise in controlling the solubility of high-molecular-weight resin and the stability of the spinning dope, leading to increased filament breakage during spinning. Supercritical carbon dioxide modification technology leverages its strong small-molecule permeability to penetrate the amorphous regions of fibers, achieving densification and reorganization for significant modulus enhancement. However, this technique requires maintaining high-pressure and high-temperature supercritical conditions, with equipment costs and safety risks posing barriers to industrialization. Surface chemical coating modification directly enhances fiber mechanical properties by introducing rigid interfacial layers, offering a simple process compatible with existing production lines. However, the chemical inertness of para-aramid surfaces results in insufficient coating adhesion strength, often causing interfacial delamination during practical use. Nanoparticle composite modification utilizes the size effects of nanomaterials to form reinforcing phases within fibers. Yet, the stringent requirement for uniform nanoparticle dispersion leads to particle agglomeration in production, creating structural defects. Molecular crosslinking strategies enhance intermolecular interactions by constructing covalent bond networks, providing a novel approach to simultaneously improve strength and modulus. However, the high stability of para-aramid molecular chains makes selective crosslinking difficult, and byproduct accumulation may compromise fiber structural uniformity. Existing modification technologies, such as molecular alignment optimization and amorphous region restructuring, enhance para-aramid modulus. Additionally, studies combining emerging methods for synergistic performance optimization have diversified technical pathways for large-scale production of high-modulus para-aramid fibers, demonstrating broad prospects for engineering applications. +++Conclusion and Prospect The research on high-modulus para-aramid fibers holds strategic significance and technical urgency. By adjusting parameters such as temperature and tension, efficient and stable heat treatment processes can be achieved, laying a solid engineering foundation for the industrial production of high-modulus para-aramid fibers. However, significant challenges remain. On the one hand, there is a need to develop high-throughput, high-precision continuous spinning equipment to reduce production costs for high-quality para-aramid fibers, and on the other hand, innovative modification methods must be explored. While current para-aramid fiber modification technologies have achieved breakthroughs in principle, practical engineering applications still face multiple contradictions involving process complexity, cost control, and performance balance. Future technological development should integrate molecular-scale design innovations with macro-process compatibility. Key priorities include deepening research on fiber structures, establishing quantifiable modulus design models, and exploring comprehensive solutions that balance performance enhancement, production efficiency, and cost control to support China's self-reliance in advanced composite materials. Moreover, in today's rapidly evolving technological landscape, efforts should expand the multifunctional dimensions of high-modulus para-aramid fibers. This involves developing next-generation fiber materials that combine ultra-high modulus, extreme environment resistance, and intelligent responsiveness, thereby driving applications in emerging fields such as smart sensing and electromagnetic shielding.

Key words: high-performance fiber, high-modulus para-aramid fiber, fiber structure, modulus, heat treatment, fiber modification