Characterization and continuous extrusion of isotropic and anisotropic poly(p‐phenylene terephthalamide)/sulfuric acid solutions to form ribbons and blown film

An experimental characterization and processing study of redissolved Kevlar® and poly(p‐phenylene terephthalamide)/sulfuric acid solutions is reported. Polarized light microscopy studies show the development of an anisotropic phase. When two phases coexist, negatively birefringent spherulites are observed. At higher concentrations, a single phase of coalescing spherulites is seen and following melting and subsequent cooling, nematic (threadlike) structures are observed. Viscosity and normal stresses were measured at various concentrations and temperatures. A yield stress is exhibited at room temperature. Both room temperature and 60°C viscosity vs concentration curves display maxima. The solution in concentration ranges from 2 to 12 percent have been extruded as ribbons and as annular blown tubular film. Processing variables and problems are discussed. Wide angle X‐ray scattering patterns of films show orientation. Tensile properties have been measured on films.