Improvements in compressive properties of high modulus fibers by crosslinking

A facile method was developed for crosslinking stiff chain polymer fibers such as Kevlar® and polybenzobisthiazoles (PBZT). The method is based on thermolysis of active aryl halides contained in the polymer unit and coupling of the free radicals formed. The method worked well for the PBZT polymers and improvements in fiber single filament recoil stress and shear modulus were demonstrated. In the case of the polyamides chain cleavage apparently accompanied the crosslinking, limiting improvement in the recoil stress test. The mode of degradation appeared to be rearrangement of the amide linkage to isocyanate.