Hydrothermal aging behavior of high‐performance polymeric fibers: Mechanical performance at the yarn scale and chemical analysis

Abstract

High‐performance fibers are used in fire‐protective garments due to their exceptional thermal stability and mechanical performance. However, these garments suffer from a reduction in their performance over their lifetime. The purpose of this study was to investigate the hydrothermal aging of 15 yarns contained in eight fabrics made of different fiber blends. The accelerated hydrothermal aging was performed via immersion in reverse osmosis (RO) and acidic water at temperatures between 40 °C and 90 °C for up to 1200 h. The resulting mechanical, chemical, and physicochemical changes in the yarns and fabrics were assessed. The result showed a large drop in the breaking force of yarns made from para‐aramid/polybenzimidazole (PBI) fiber blends in all aging water conditions. For the other fabrics, aging in acidic water and a jar with the PBI‐containing fabrics generally caused a larger decrease in strength compared to aging in RO water in a separate jar. The results also showed that a change in crystallinity rather than in chemical structure appeared to be the cause for the changes in tensile strength after hydrothermal aging. The findings of this study will contribute to identifying strategies to improve the long‐term performance of fire‐protective fabrics.

Thermal aging of high‐performance fabrics used in the outer shell of firefighters' protective clothing

“…For example, the stretching of N H (around 3300 cm À1 ), vibration of F I G U R E 9 Attenuated total reflectance-Fourier transform infrared spectroscopy spectra of Technora ® , para-aramid, metaaramid, polybenzimidazole (PBI), and polybenzoxazole (PBO) fibers. Data for para-aramid, meta-aramid, PBI, and PBO fibers from Hoque et al 48 [Color figure can be viewed at wileyonlinelibrary.com] C N/C N H (around 3065 cm À1 ), stretching of C O (around 1640 cm À1 ), and vibration of poly (3,4 0 -diphenyl ether terephthalamide) (series of peaks around 1250 cm À1 ) demonstrated the presence of Technora ® fibers in Fabric SA. The presence of PBO fibers in Fabric SA's yarns was confirmed with the peak at 699 cm À1 (oxazole ring vibration).…”