Effects of a Multifunctional Polymeric Chain Extender on the Properties of Polylactide and Polylactide/Clay Nanocomposites

A multifunctional polymeric chain extender (Joncryl) was used in the melt processing of a neat polylactide and polylactide/clay nanocomposites. The effects of Joncryl on morphology, rheology, thermal and mechanical properties, barrier properties and biodegradability were investigated. Three Joncryl loadings (0.1, 0.3 and 0.5 wt%) were used in this study, and the 0.5 wt% loading induced a long-chain branched structure in the PLA matrix, as indicated by the melt rheology results. It is believed that the property variations are all related to the long-chain branched structure as well as on the molecular weight recovery. The use of Joncryl did not change the intercalated and partially exfoliated clay structures in the PLA/clay nanocomposites, as observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The tensile modulus and maximum strength slightly increased with Joncryl loading. The oxygen barrier properties were also improved by adding Joncryl. However, the addition of Joncryl prevented the formation of large spherulitic crystals and decreased the creep resistance at low stress level. Joncryl could not only control the thermal degradation of PLA during processing, but also affected its biodegradation in compost: higher Joncryl loading led to slower biodegradation and less molecular weight reduction with time.