Microcellular foams of glass–fiber reinforced poly(phenylene sulfide) composites generated using supercritical carbon dioxide

Microcellular foaming of poly(phenylene sulfide) (PPS) and its glass–fiber (GF) reinforced composites using supercritical CO₂ as a blowing agent presents a promising approach to produce novel cellular materials with tailored microstructures. This study investigated the effects of the material composition and process conditions on the foaming behaviors and final morphologies of the microcellular foamed PPS and PPS/GF composites. The rheological and thermal properties as well as the saturation and desorption behaviors of CO₂ in the pure PPS and PPS/GF composites were also detailedly discussed. The results show that microcellular foams with various relative densities, cell sizes, cell-size distributions, and cell densities can be attained by tailoring the fiber content and key process parameters. At low foaming temperatures below the cold crystallization temperature, the microcellular foamed PPS and PPS/GF composites both present a unimodal cell-size distribution. At elevated temperatures, the generated crystalline superstructures including spherulites in the polymer matrix and transcrystals around the GF will cause a secondary heterogeneous cell nucleation. This leads to the observations of bimodal and trimodal cell-size distributions in the pure PPS and the PPS/GF composites, respectively. The mechanisms for the solid-state foaming behaviors of pure PPS and PPS/GF composites have been illustrated by establishing theoretical models. POLYM. COMPOS., 37:2527–2540, 2016.