Changes in the Structure of Wet-Spun Acrylic Fibers During Processing

The structural changes that occur during processing of a wet-spun 93% polyacrylonitrile -7% polyvinyl acetate co polymer are discussed. Stress-strain, x-ray diffraction, shrinkage, and electron microscopy data are explained in terms of a model in which the molecules are in an irregular helical conformation in the relaxed state and can extend during de formation. The molecules are arranged in fibrils which, in turn, form a three-dimensional network. The fibrillar ele ments remain intact through the coagulation, hot-stretching, and drying, although network junctures break and reform. The model proposed is an extension of that used by Rosenbaum to describe the behavior of acrylic fibers after processing and is in agreement with previous work on the structural characterization of polyacrylonitrile.