Elastomeric foam prepared by supercritical carbon dioxide

Abstract

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 μm 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. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44354.

TPU/PLA blend foams: Enhanced foamability, structural stability, and implications for shape memory foams

“…Though efforts have been made to increase nucleation, improve mechanical properties, remove skin layer, and improve foam expansion of TPU foams, study on reducing foam shrinkage has not been reported. TPU elastomer foams could undergo substantial foam shrinkage, like other elastomer and rubber foams . Typically, elastomers have T g that is well below T r , which can prevent T g from acting as the anchor point to fix the foamed structure.…”

Foaming of poly(ethylene‐co‐vinyl acetate) and poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) and their blends with carbon dioxide

“…There are other complications; for example, a common phenomenon observed in the foaming of elastomers such as poly(1,4‐butylene terephthalate) ‐co‐ (1,4‐butylene adipate) is the post‐expansion of the polymer after removal from their foaming molds. This arises from the low (below room temperature) T g and the residual CO 2 remaining in the polymer which causes the further foaming at room temperature . In some other systems such as styrene‐ethylene‐butylene‐styrene (SEBS) elastomers and also in foams generated from poly(ethylene ‐co‐ octene), instead of postfoaming expansion, foam shrinkage is observed which is attributed to the elasticity of the polymer.…”