Development of high void fraction polylactide composite foams using injection molding: Crystallization and foaming behaviors

Polylactide (PLA) composite foams with two different void fractions of 30% and 55% were developed using regular foam injection molding (FIM) and FIM with mold opening, respectively. The microcellular structure and crystallization behavior were characterized using scanning electron microscopy and differential scanning calorimetry. The crystallization kinetics of the unfoamed samples was also analyzed with and without the presence of dissolved nitrogen (N₂). The results showed that the presence of nanoclay and talc, presence of pressurized N₂, foaming action, and mold opening all enhanced the PLA's crystallization kinetics during injection molding, leading to a threefold increase in the final crystallinity. Consequently, the presence of nanoclay/talc together with the expedited crystallization enhanced the PLA foams' morphology with a finer and more uniform cell structure (cell size<50μm) at a void fraction of 55%. The mechanisms of the formation of such morphologies were also derived.