Abstract:

Objective Among various textile materials, meta-aramid has become an important material in the field of protective clothing due to its excellent performance. However, its inadequate comfort limits its application in certain scenarios. Sericin protein possesses excellent hydrophilicity and shows potential for improving the wearing comfort of meta-aramid fabrics. Therefore, enhancing the hydrophilic properties and overall wearing comfort of meta-aramid through surface grafting modification methods holds significant importance for improving the comprehensive functional performance and wearing comfort of protective clothing.

Method In this study, Friedel-Crafts alkylation was employed to introduce epoxy groups onto the surface of the aramid fibers, followed by the grafting of sericin protein. Then, the grafting of sericin onto the aramid fibers was analyzed by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and Coomassie Brilliant Blue staining experiment. Furthermore, the washability, thermal stability, comfort, and flame retardancy of the fabrics before and after modification were characterized and evaluated.

Results Through Friedel-Crafts alkylation, active sites were successfully introduced onto the surface of meta-aramid fibers, enabling the stable chemical bonding of sericin protein to the fibers. This process endowed the modified fabric with excellent wash resistance, resulting in a sericin retention rate of over 75% after 30 washing cycles. FE-SEM revealed characteristic morphological changes on the surface of the modified fibers, including uniform deposition of sericin protein and filling of fiber gaps, without compromising the integrity of the fiber structure. EDS confirmed a significant increase in oxygen content on the fabric surface, indicating the successful introduction of oxygen-containing functional groups. FT-IR and Coomassie Brilliant Blue staining experiments further verified that sericin protein was successfully grafted onto the fabric surface. The modified fabric maintained good thermal stability, while its performance underwent significant changes, where the areal density increased by 50%, moisture regain improved by 17.4%, and wicking height increased by 40.2%. The peak electrostatic voltage decreased by 59.2%, demonstrating substantial enhancements in hydrophilicity, moisture conductivity, and antistatic properties. Although air permeability and moisture permeability decreased by 8.8% and 1.5%, respectively, they remained within acceptable ranges. In terms of flame retardancy, compared with the original fabric, the after-flame time of the modified fabric in the warp and weft directions increased by 0.26 s and 0.28 s; the afterglow time in the warp and weft directions increased by 0.34 s and 0.26 s, and the damaged length in the warp and weft directions increased by 1 mm and 4 mm. Although these parameters increased slightly, but still satisfying the flame-retardant standards.

Conclusion Based on the experimental results, the Friedel-Crafts alkylation reaction effectively facilitated the bonding between sericin and meta-aramid, resulting in an overall improvement in the wearing comfort of the grafted aramid fabric. The modified fabric retains its classification as a flame-retardant material. The surface grafting technology based on Friedel-Crafts alkylation not only significantly enhances the fabric's hydrophilicity and wearing comfort but also preserves its inherent flame-retardant functionality. With its maintained excellent flame retardancy and improved wearing comfort, the modified aramid fabric is suitable for professional applications requiring prolonged wear, such as firefighting suits and industrial protective clothing. It holds the potential to effectively address common issues associated with traditional protective garments, such as heat retention and static electricity buildup. This study achieves a synergistic enhancement of the "protection-comfort" performance of aramid fabrics, providing an effective technical pathway for developing protective textiles that combine high performance with superior comfort.

Key words: sericin protein, meta-aramid, wearing comfort, surface modification, hydrophilicity, flame retardancy, Friedel-Crafts alkylation, high-performance fiber