Expansion and dimensional stability of semi-crystalline polylactic acid foams

In this study, semi-crystalline PLA was foamed using CO2 as the blowing agent. The samples were foamed under various conditions of CO2 concentration, foaming temperature and foaming time. The samples were characterised by differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). Their dimensional stability was also assessed at 70 °C. Results showed that dimensional stability was strongly related to the expansion ratio of the foam and the strain-induced crystallinity developed during foaming. Shrinkage at 70 °C virtually disappeared with crystallinity above 40% (expansion ratio of approximately 40), in accordance with published data.