Challenge to Forty-Fold Expansion of Biodegradable Polyester Foams Using Carbon Dioxide as a Blowing Agent

Abstract

This paper presents a new foaming technology using supercritical carbon dioxide as a blowing agent to obtain large volume expansion of biodegradable polyester foams of over forty-fold. The basic approach for the promotion of a large volume expansion ratio with carbon dioxide was to prevent cell coalescence by using a branched material, to completely dissolve carbon dioxide in the melt by promoting convective diffusion under a high processing pressure, to reduce the diffusivity of gas by lowering the melt temperature, and to optimize the processing conditions in the die to maximize volume expansion. The desirable composition of the materials includes dehydrated branched biodegradable polyester (polybutylene succinate), CO² (blowing agent), and talc (nucleating agent). A single-screw extrusion system was used for foam processing. A large volume expansion ratio of up to 45 fold was successfully achieved from the biodegradable polyester foams. The morphologies and volume expansion ratios of biodegradable polyester foams at various processing temperatures and pressures were studied.