Microstructure and Thermal Behavior of Polylactide/Clay Nanocomposites Melt Compounded under Supercritical CO2

Supercritical carbon dioxide (Sc-CO2) is a good plasticizer to improve the compatibility for nanocomposites or polymer blends. In this work, polylactide (PLA)/clay nanocomposites were compounded using a twin-screw extruder. Two extrusion methods were used, one with Sc-CO2 and another without Sc-CO2. Microstructures of nanocomposites and their mechanical properties were investigated. Their thermal behavior was analyzed using differential scanning calorimeter (DSC) and thermogravimetry analyzer. Results show that the layer spacing of clay in the nanocomposites was improved. Observed from transmission electron microscopy photomicrographs, it was shown that the clay was dispersed more homogeneously in the nanocomposites compounded with Sc-CO2. DSC traces show that cold crystallization appeared for nanocomposites, indicating that clay could act as a nucleating agent. Sc-CO2 was helpful in improving the thermal stability of nanocomposites. In addition, there existed a yielding phenomenon for nanocomposites during the tensile property measurement. With the preparation of Sc-CO2, the elongation at break and tensile strength for nanocomposites were increased. (C) 2011 Wiley Periodicals, Inc. Adv Polym Techn 30: 174-182,2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20214