Macrostructural changes in thermally treated viscose fibers due to cold drawing process

The molecular orientation of thermally treated viscose (rayon) fibers was investigated by two techniques. The mechanical parameters, which were obtained by a micro-stress-strain device in conjunction with an interference microscope, and structural parameters, which gave the optical properties, of boiled viscose fibers for different intervals of time and cold drawn at room temperature were calculated. The changes in the stress and draw ratios were evaluated to obtain the shrinkage factor, uniaxial tension, and true stress and orientation factors [P2(cos theta)] and [P4(cos theta)]. The functions f(2)(theta), f(4)(theta), and f(6)(theta) were also calculated. The dielectric constant, dielectric susceptibility, number of moles in physical network chains between entanglements in the semicrystalline phase per unit volume, surface reflectivity, segment anisotropy, number of chains between crosslinks per unit volume, and number of crystals per unit volume were among the evaluated parameters. An empirical formula was suggested to correlate the changes in the evaluated parameters with different draw ratios, and its constants were determined. The study demonstrated changes in the molecular orientation factors and the evaluated macrostructural parameters as a result of applied stress and the boiling effect. (C) 2001 John Wiley & Sons, Inc.