Coloration in acrylonitrile polymers

The heat coloration and alkali coloration of PAN was investigated with model compounds by measuring infrared absorption spectra and ultraviolet absorption spectra. Some of the information obtained from this work supported the opinion of Grassie et al., who proposed the formation of partly hydrogenated naphthyridine‐type structure to explain the alkali coloration of PAN. The intramolecular ring closure mechanism of the initiation to propagate to the partly hydrogenated naphthyridine‐type structure of heat‐treated PAN proposed by Grassie et al., which, however, may involve the dehydrogenated structure somewhere, was supported, too. On the other hand, the formation of intermolecular azomethine‐type crosslinking structure proposed by Schurz et al. was not supported by any results of the experiments with model compounds.