Effect of processing conditions on the cell morphology distribution in foamed injection molded PLA samples

Foam injection molding uses physical blowing agents under high pressure and temperature to produce structural foams having a cellular core and a compact solid skin. This technology is particularly interesting for biodegradable polymers, which often present a very narrow processing window, with the suitable processing temperatures close to the degradation conditions. The addition of a supercritical gas can lead to the reduction of both the viscosity and the glass transition temperature of the polymer melt, which therefore can be injection molded adopting lower temperatures and pressures. In this work, the effect of different processing parameters on foam morphology of Poly(lactic) Acid, PLA, was studied. In particular, two commercial grades of PLA having different rheological properties were adopted to obtain foamed parts by injection molding process with nitrogen as a physical blowing agent. For both PLA grades, the effect of mold temperature on the crystallinity and the resulting cell morphology was assessed.