Expanded polylactic acid - an eco-friendly alternative to polystyrene foam

Abstract

A commercially viable process to manufacture low-density expanded polylactic acid (E-PLA) products with environmental-friendly blowing agents such as carbon dioxide has been developed. The resulting material is a sustainable alternative to expanded polystyrene (EPS). The E-PLA has thermal conductivity and mechanical properties comparable to EPS and can be used in many similar applications. The process involves impregnation of PLA beads with carbon dioxide and fusing with heat, including steam heating. Gel permeation chromatography indicated that the PLA polymer molecular weight was not degraded by the foaming or steam heating process. Visual characterization showed that under some circumstances, PLA precursor beads exhibited voids, which disappeared during CO2 impregnation indicating some form of rearrangement or realignment of the polymer morphology or structure. Due to the effect of CO2 on the glass transition temperature of the PLA, a linear reduction of 5.5°C per wt% of absorbed CO2 was observed.