Heterogeneous Cell Nucleation Mechanisms in Polylactide Foaming

At present, most polymeric products are derived from fossil fuels, and they become nondegradable waste materials in the environment. Consequently, global efforts are being made to create green polymers from renewable resources, which are also biodegradable and compostable. Poly(lactic acid) or polylactide (PLA) is a biodegradable and biocompatible polymer produced from renewable resources such as cornstarch and sugarcane (Grijpma and Pennings 1994; Perego et al. 1996; Sinclair 1996; Tsuji and Ikada 1998; Martin and Averous 2001). It is a thermoplastic aliphatic polyester that is synthesized through the ring-opening polymerization of lactide and lactic acid monomers (Lunt 1998; Drumright et al. 2000; Gupta et al. 2007), as shown in Figure 5.1. Over the last decade, PLA has attracted extensive industrial and academic interests as a potential substitute for petroleum-based polymers, which are used in both commodity and biomedical applications. This is not only due to its green and biodegradable features but also because it releases no toxic components during the manufacture.