Polylactide/montmorillonite nanocomposites and microcomposites prepared by melt blending: Structure and some physical properties

Polylactide (PLA)/clay nanocomposites loaded with 3 wt % organomodified montmorillonite and PLA/clay microcomposites containing 3 wt % sodium montmorillonite were prepared by melt blending. We investigated the morphology and thermal properties of the nanocomposites and microcomposites and compared them with unfilled PLA, keeping the same thermomechanical history. The influence of the processing temperature on the structural characteristics of the investigated systems was determined. The investigations were performed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), size exclusion chromatography (SEC), and polarized light microscopy (LM). XRD showed that the good affinity between the organomodified clay and the PLA was sufficient to form intercalated structure in the nanocomposite. The microcomposite featured a phase-separated constitution. DSC and LM studies showed that the nature of the filler affected the ordering of the PLA matrix at the molecular and supermolecular levels. According to TGA, the PLA-based nanocomposites exhibited improvement in their thermal stability in air. Reduced flammability, together with char formation, was also observed for nanocomposites, compared to the microcomposites and pure PLA. (C) 2002 Wiley Periodicals, Inc.