Abstract
The fine structure of a high-strength homopolymer-type polyacrylonitrile (PAN) fiber prepared by additional heat drawing after usual wet spinning was investigated using wide (WAXD) and small (SAXS) angle X-ray scattering in comparison with those of ordinary homo- and copolymer-type PAN fibers prepared by usual wet spinning method. WAXD data were analyzed by a cylindrical distribution function (CDF) method. The meridional section of CDF showed that the crystal chain has a fiber periodicity of 2.5A in all these three kinds of fibers. The periodicity deteriorated at 12A and 10A in the high-strength homopolymer fiber-type and homo-and copolymer-type fibers. The CDF equatorial section of the high strength homopolymer-type fiber showed peaks at 6.5A, 11.8A and 16.4A. For investigating the long spacing, the meridional SAXS intensity of the fibers was measured before and after thermo-oxidative treatment at 200°C-300°C. Both ordinary homo- and copolymer-type fibers showed SAXS peaks due to the long spacing after oxidative heat-treatment. In the case of high strength homopolymer-type fiber, however, no SAXS peak appeared even after thermo-oxidation. This is the most important structural character of the high strength homopolymer-type fiber.
