Oxidative Stabilization of Acrylic Fibers. V. The Decoloration Reaction

摘要

When acrylic fibers are heat treated for various times at 220-250 C, they form dark, insoluble structures of uncertain chemical character which are inert to many strong oxidizing and reducing agents. The heat-treated fibers are, however, rapidly decolored by warm alkaline hypochlorite solutions. When fibers which have undergone short time heat treatment are subjected to the hypochlorite, incubation periods are observed before decoloration is noted; and a swollen acrylic network remains after decoloration is complete. The acrylic network is primarily unreacted precursor units save for a small amount of hydrolyzed material. The decoloration reaction is zero order, indicating a reaction at the surface. Prior to the decoloration reaction, there is a penetration or plasticization of the subsurface material by elements of the solution, as indicated by the presence of chlorine atoms in the interiors of exposed fibers. The rate of the decoloration reaction increases with increasing duration of the stabilization heat treatment. The precise structure of the final material depends therefore on the original fiber composition and the processing variables.