Challenge to forty-fold expansion of biodegradable polyester foams using carbon dioxide as a blowing agent

This paper presents a new foaming technology using supercritical carbon dio xide as a blowing agent to obtain large volume expansion of biodegradable p olyester foams of over forty-fold. The basic approach for the promotion of a large volume expansion ratio with carbon dioxide was to prevent cell coal escence by using a branched material, to completely dissolve carbon dioxide in the melt by promoting convective diffusion under a high processing pres sure, to reduce the diffusivity of gas by lowering the melt temperature, an d to optimize the processing conditions in the die to maximize volume expan sion. The desirable composition of the materials includes dehydrated branch ed biodegradable polyester (polybutylene succinate), CO2 (blowing agent), a nd talc (nucleating agent). A single-screw extrusion system was used for fo am processing. A large volume expansion ratio of up to 45 fold was successf ully achieved from the biodegradable polyester foams. The morphologies and volume expansion ratios of biodegradable polyester foams at various process ing temperatures and pressures were studied.