Elastomeric foam prepared by supercritical carbon dioxide

Biodegradable elastomer poly[(1,4-butylene terephthalate)-co-(1,4-butylene adipate)] foam was successfully prepared using supercritical CO2. The elastomer foam has closed and uniform cell structure with density about 90 g/L. Narrow size distribution with average cell diameter 32 m were obtained. The foamed balls show rubbery properties and can recover well (>90%) to their original shape quickly after releasing press stress. Cell growth needs to take place at melting state where the migration and orientation of polymer chains are permanently kept without remained force of springback. Some unique phenomena were observed during foaming the elastomer: post-expansion (about 40%) was obtained after removing the foamed samples from a cylinder mold, which results in forming a ball rather than a cylinder like the mold. This phenomenon was explained by the lower glass transition temperature of the elastomer, in which residual CO2 foam continuously in the room temperature; and memory of internal strength. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44354.