Tensile deformation of nylon 6 fibers

Abstract

Abstract Nylon 6 fibers which had been relaxed to different extents by annealing were examined at fixed strains by small angle and wide angle X‐ray techniques. It was found that the strain of the long period of the semicrystalline microfibrils is identical to the macroscopic fiber strain. Approximately 1/3 of the tensile deformation results from molecular shear of imperfectly oriented crystalline chains. Virtually no evidence for intercrystalline slip is found; the orientation of the intercrystalline amorphous regions results in a low compliance for the shear of crystals past one another. The majority of the microfibril deformation occurs by stretching these intercrystalline amorphous regions, accompanied by the flow of extrafibrillar amorphous material to maintain constant volume. In highly annealed fibers this “filling” mechanism is less efficient, as the amount of extrafibrillar material has been reduced during shrinkage. This effect leads to a decrease in Poisson's ratio after increasingly severe annealing. A related result of annealing is the dehomogenization of the microstructure, leading to the presence of more stress‐induced “microcracks” during the stretching of annealed fibers.