What Does LiOH Treatment Offer for Lyocell Fibers? Investigation of Structural Changes

Abstract

Lyocell fibers, regenerated cellulosic fibers spun from cellulose/N-methylmorpholine-N-oxide hydrate solution by wet spinning, were treated with LiOH aqueous solution at concentrations of up to 7.5 M to study the inter-and intrafibrillar changes. Wide-angle X-ray diffraction analyses were applied to identify the crystallinity index and crystallite size. Inverse size-exclusion chromatography was applied to study the pore structure of the swollen fibers. The mean pore diameter was found to increase after the LiOH treatment. The carboxyl content, measured by methylene blue sorption, decreased slightly. The water retention value, depth of color measured after dyeing with CI Direct Red 81, and weight loss of fibers changed gradually after LiOH treatment at concentrations up to ca. 5 M. The treated fibers became brittle as a result of both inter-and intrafibrillar swelling and the deep penetration ability of LiOH treatments above 5 M.