Masayasu Itoh and Akira Kabumoto
Microcellular plastic (MCP) is a polymeric foam with an average cell size of 10 µm or less. The basic process for MCP was proposed in 1981 by Professor Suh at the Department of Mechanical Engineering of MIT in the U.S., and the process has been applied to various plastic materials. In this work, the effects of crystallization of microcellular polyphenylene sulfide (PPS) on its morphology are investigated. When PPS was foamed below its crystallization temperature, a unimodal distribution was observed with a cell size of about 10 µm. When foamed above its crystallization temperature, on the other hand, a bimodal distribution was observed with two peaks at about 10 µm and the submicron order in cell size. It was shown that these submicron-sized cells were generated by cell nucleation induced by crystallization of PPS.