Thermal stability of poly(l-lactide)/poly(butylene succinate)/clay nanocomposites

Composites of poly(l-lactide) (PLLA)/poly(butylene succinate) (PBS) with an organophilic clay having a special functional group, namely twice-functionalised organoclay (TFC) were prepared. TFC was produced by treating the commercially available organoclay (Cloisite25A) (C25A) with (glycidoxypropyl)trimethoxy silane (GPS). The morphological structure of nanocomposites was analysed by using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The silicate layers of PLLA/PBS/TFC were exfoliated to a larger extent than PLLA/PBS/C25A. Not only tensile modulus and tensile strength but also elongation at break of PLLA/PBS was greatly enhanced as a result of melt compounding with TFC. The larger amount of exfoliation of the silicate layers in PLLA/PBS/TFC as compared with that in PLLA/PBS/C25A was attributed to the increased interfacial interaction between the polyesters and the clay through chemical reaction. Thermo gravimetric analysis revealed that both T5%, which was the temperature corresponding to 5% weight loss, and activation energy of thermal decomposition of PLLA/PBS/TFC were far superior to those of PLLA/PBS/C25A as well as to those of PLLA/PBS, indicating that the composites with exfoliated silicate layers were more thermally stable than those with intercalated silicate layers.