(665a) Microcellular Injection Molding of Polylactide and Polylactide-Montmorillonite Nanocomposites

Polylatide (PLA) has gained much interest in recent years because it is a biobased polymer with some unique material properties, such as a very high modulus and relatively high strength. However, widespread application of PLA has been limited by its brittleness, narrow processing window and relatively high cost. Microcellular injection molding is capable of producing lightweight and dimensionally stable components with a complex geometry at a reduced temperature and pressure while potentially improving some of the material properties such as impact strength and fatigue life. This presentation will discuss the effects of adding montmorillonite (MMT) nanoclay (Cloisite®20A and 30B) on the mechanical properties (specific modulus, specific tensile strength, specific toughness, and strain-at-break) of both solid and microcellular PLA components, as well as their effects on the cell morphology of the microcellular components. In general, the addition of nanoclay into biobased PLA improved the specific moduli of both solid and microcellular components and facilitated the formation of a smaller cell size and a higher cell density. In addition, adding nanoclay reduced the strain-at-break and specific toughness of solid PLA nanocomposite components. However, the strain-at-break and specific toughness of microcellular PLA nanocomposites were largely improved in comparison to that of the microcellular PLA neat resin, especially when the loading level of the MMT was at 3 and 5%, presumably due to the lack of large voids as well as the smaller cell size and higher cell density. Microcellular PLA nanocomposites with a MMT loading level at 3 or 5% also possessed a somewhat higher strain-at-break and specific toughness than their corresponding solid PLA nanocomposites.