A simple method for preparation of microcellular PLA/calcium carbonate nanocomposite using super critical nitrogen as a blowing agent: Control of microstructure

A simple method was used to prepare microcellular foams of poly(lactic acid) (PLA) and its nanocomposites to improve its shortcomings such as low impact resistance and high cost. The batch foaming process of pure PLA and PLA filled with Nano calcium carbonate (NCC) was conducted using supercritical nitrogen (N-2) as a blowing agent. The effect of NCC on crystallization of PLA is discussed as a remarkable parameter in foaming of semicrystalline polymers. Differential scanning calorimetry (DSC) was used to optimize the process temperature. The effect of foaming conditions (temperature, pressure, and cooling rate) and nanoparticle content on the foam microstructure of PLA and its nanocomposites were investigated using scanning electron microscopy (SEM). Foams were obtained in the range of macro- and microscale (different cell sizes) using different foaming conditions. The results revealed that nanoparticles show excellent nucleation performance on PLA foaming. Results of dynamic mechanical thermal analysis (DMTA) also showed significant influences of NCC on foamed and prefoamed samples to different foaming structures.