A double bubble tubular film process to produce biaxially oriented poly(p‐phenylene sulfide) (PPS) film

A double bubble tubular film process to produce biaxially oriented poly(p‐phenylene sulfide) (PPS) film is described. Operating windows were developed for stable operation of both the first and second bubbles. Films produced from single bubble tubular film extrusion were largely amorphous having only seven to nine percent crystallinity. Double bubble PPS tubular film had up to 20 percent crystallinity which was increased to 30 percent by further annealing. The first and second bubble films had surface roughness standard deviation heights of 0.01 to 0.04 μm. Orientation was characterized by birefringence and wide angle X‐ray diffraction pole figures of the 110 and 112 reflections. Biaxial orientation factors were computed. The double bubble films had higher Young's modulus and tensile strength but lower elongation to break than the single bubble films. Annealing further increases Young's modulus and tensile strength but decreases elongation to break. Double bubble and annealed films with roughly equal second bubble drawdown ratio and second blow up ratio tend to have balanced properties in the plane of the film.