Effect of clay type and loading on thermal, mechanical properties and biodegradation of poly(lactic acid) nanocomposites

PLA nanocomposites based on two different clays (CLO30B and SOMMEE) at 5 and 10wt.% clay loading were prepared by melt-blending, obtaining a good level of clay dispersion as well as considerable thermo-mechanical improvements in PLA, according to WAXS, SEM, TEM, DMTA and tensile strength analysis. Addition of clays induced PLA crystallization by nucleation, especially upon addition of SOMMEE, promoting kinetics and extent of crystallization of the polymer, especially at high clay content. Concerning the thermal and mechanical properties, the highest improvements in PLA matrix were obtained upon 10% clay addition, especially SOMMEE, becoming more noticeable with increasing temperature. An effective degradation of PLA and nanocomposites in compost at 40°C was also achieved. It was found that addition of nanoparticles, especially SOMMEE, accelerated the degradation process of PLA, particularly at higher clay content, probably due to catalysis by the hydroxyl groups belonging to the silicate layers surface and/or to their organic modifier.