Fabricating the Strongest and Toughest Aramid Fibers by Small Addition of Carbon Nanotubes

Abstract Synthetic high-performance fibers, such as polyaramid fibers, have attracted particular attention owing to their excellent mechanical properties and promising applications in safety protection fields. However, fabricating fibers with high strength and toughness is challenging due to their intrinsic conflicts. Herein, we report a simultaneous improvement in strength and toughness of heterocyclic aramid fibers by 26% and 66%, respectively, via in situ polymerizing small amount (0.05 wt%) of short aminated single-walled carbon nanotube (SWNT) into heterocyclic aramid fibers, yielding 6.44 ± 0.11 GPa in tensile strength and 184.0 ± 11.4 MJ m−3 in toughness. Combined experimental evidences and atomistic simulations, it was uncovered that short aminated SWNTs with favorable dispersity and alignment significantly improve the crystallinity and orientation degree of heterocyclic aramid chains by a scope of 8.6 nm, and the in situ polymerization between short aminated SWNTs and heterocyclic aramid monomers increases the length of polymer chains and the interfacial interaction therein to promote stress transfer and suppress the strain localization. These two effects account for the simultaneous improvement in strength and toughness of heterocyclic aramid fibers via small addition of short aminated SWNTs. This composite manner of “small addition, big gains” through global optimization should guide further work on improving the strength and toughness of composites.