Process for the formation of biaxially oriented films of poly(p‐phenylene terephthalamide) from liquid crystalline solutions

Abstract

AbstractA new process for making equal biaxially oriented films from liquid crystalline solutions of poly(p‐phenylene terephthalamide) (PPD‐T) is described. The process involves extruding solutions of PPD‐T/H2SO4 through an annular die and over an oil‐coated mandrel into a coagulation bath. The films were studied using wide angle X‐ray diffraction (WAXS) and scanning electron microscopy (SEM). Tensile stress–strain properties were obtained on samples cut at various directions in the plane of the film. Biaxially oriented films which possess equal properties in the various directions in the plane of the film were produced. Moduli of 2.3 × 109 Pa and tensile strengths of 9.6 × 107 Pa were obtained in the plane of the film. Films with unequal biaxial orientation were also produced. These tend to have higher modulus/tensile strength in the direction of major orientation, the machine direction (up to 8.3 × 109 Pa/2.5 × 108 Pa), but become brittle in the transverse direction.