Optimizing p-aramid copolymer superfibers: The synergistic effect of solution rheology and fiber structure

Abstract

Para-aramid (p-aramid) fibers have gained significant attention in lightweight vehicle and optical cable industries. However, the use of harsh sulfuric acid-based processing limits their widespread adoption. As a promising alternative, p-aramid copolymer (p-AC) offers improved processability while maintaining comparable properties. In this study, p-AC superfibers incorporating 3,4′-oxydianiline (3,4′-ODA) monomers were successfully fabricated through optimized manufacturing processes spanning from solution preparation to fiber property enhancement. The homogeneity of spinning solutions, determined by polymerization conditions, serves as a key factor governing fiber structure and properties. Three p-AC solutions with varying rheological homogeneities, classified as low (L), moderate (M), and high (H), exhibited Cole-Cole plot slopes of 1.12, 1.34, and 1.65, respectively. A higher solution homogeneity enabled greater draw ratios, leading to more compact and well-aligned fiber microstructures. Consequently, as the homogeneity increased, the fiber crystallinity and orientation factor increased from 56.1 % and 0.923 to 62.2 % and 0.968, respectively. Notably, the p-AC-H fibers exhibited tensile modulus and strength of 82.4 and 3.1 GPa, respectively, representing 11.2 % and 41.0 % increases compared to those of p-AC-L fibers (74.1 and 2.2 GPa, respectively). These findings establish a direct correlation between solution homogeneity and fiber performance, providing a theoretical background for the precise design of high-performance superfibers.