THE RADIAL HETEROGENEITY OF POLYVINYL ALCOHOL FIBERS

Abstract

Polyvinyl alcohol (PVA) fibres are prepared by wet, dry and semi-melt spinning methods, and the micro-structural heterogeneity along the radius of the fibers was examined by means of the phase contrast as well as polarization-microscopical observations. Futhermore, those fibres are stripped to various extent according to the Elöd's peeling off method, and then its apparent density, small angle X-ray scattering intensity, crystallinity, crystallite-size, iodine adsorption, birefringence, crystalline orientation and mechanical properties are measured.
Cross-sections of the fibres washed in water after coagulating in conc. sodium sulfate bath are apparently homogeneous, but cuticle and skin layers are distinguishable from the core layers by means of phase contrast-microscopical observation. The radial structures and properties of the fibres coagulated in a caustic soda are comparatively homogeneous. Marked skins are formed on the dry spun fibres, while the sections of semi-melt spun fibres are uniform.
The effects of spinning conditions on the radial structures of fibres are discussed briefly.