EFFECT OF HEAT-TREATMENT ON STRUCTURAL-CHANGES AND DYNAMIC-MECHANICAL RELAXATION OF POLYACRYLONITRILE FIBERS

The structural changes of polyacrylonitrile fibers have been studied through the effect of heat treatment on dynamic mechanical relaxation of undrawn and drawn fibers. It is generally accepted that polyacrylonitrile has two transition temperatures. This study showed that the activation energies of the low temperature transition and the high temperature transition were about 53 and 155kcal/mole, respectively. The latter was related to the intermolecular diploe-dipole dissociation of the nitrile groups in the amorphous region and the former was related to the molecular motion in the paracrystalline region.