Preparation of biodegradable PBST/PLA microcellular foams under supercritical CO2: Heterogeneous nucleation and anti-shrinkage effect of PLA

A series of fully biodegradable poly(butylene succinate-butylene terephthalate) (PBST)/poly (lactic acid) (PLA) microcellular foams were prepared by using supercritical carbon dioxide as the blowing agent. The addition of PLA exhibited a typical “sea-island” morphology, which could not only increase the crystallization temperature of PBST, but also improve the rheological properties of PBST in the low frequency region. The uniform microcellular structure with the smallest cell diameter (7.1 μm) and the highest cell density (3.5 × 1010 cells/cm3) was successfully prepared with 20 wt% PLA blend at 90 °C. PLA mainly played a role of heterogeneous nucleation in the foaming process when the content increased from 0 to 20 wt%. With the further increased content, PLA affected the foaming process by regulating the solubility and diffusion behavior of CO2 in the blends, resulting in severe cell collapse and coalescence. The 80/20 blend of PBST and PLA exhibited the highest expansion ratio of 17 without shrinkage. The existence of PLA could facilitate the formation of open-cell structure and enhance the rigidity of the blends, effectively solving the shrinkage problem of PBST foams.