Abstract
Concentrated solution of polyacrylonitrile in 70% nitric acid was extruded in 36% nitric acid and scoured after coagulation. The coagulated threads were stretched at 100°C in hot water.
From X-ray diffraction measurement, it was found that the degree of crystallinity and size were not independent of the molecular weight and drawing ratio. By heat stretching of coagulated threads, highly orientated fiber is obtained easily in the case of low molecular weight. On the contrary, polymer chains of high molecular weight do not highly orient by the heat stretching at 100°C. For fibers having same orientation, tensile strength increases rapidly with the molecular weight. These phenomena are well explained by molecular theory.
