Microstructure and non-isothermal crystallization behavior of PP/PLA/clay hybrid nanocomposites

Abstract

Various compositions of polypropylene (PP) and poly(lactic acid) (PLA) blends were prepared by one-step melt compounding in a twin-screw extruder. Two compositions were selected for investigation of effect of clay and n-butyl acrylate glycidyl methacrylate ethylene terpolymer (PTW) as compatibilizer on thermal properties and non-isothermal crystallization behavior of PP/PLA/clay nanocomposite systems, i.e., PP-rich one (75/25 composition) containing Cloisite 15A and PLA-rich one (25/75 composition) containing Cloisite 30B. The thermal behavior of the systems was investigated by means of differential scanning calorimetry (DSC) and correlated with their microstructures. The narrowing down of the peaks in the wide-angle X-ray scattering pattern of PP-rich blend was associated with an increase in size and/or perfection of the crystals. On the other hand, the broadening of the peaks in PLA-rich blend implied a decrease in the size of the crystals. The calculated interlayer distance, using Scherrer equation, in Cloisite 15A was slightly greater than that of Cloisite 30B. Moreover, an increase of 100 % in interlayer distance showed a greater level of intercalation in PP-rich system as compared to the PLA-rich system. Blending of PP and PLA led to significant changes in the crystallinity behavior of the blends compared to the neat components. Moreover, the incorporation of the both clays into the two systems led to a greater change in the crystallinity degree, comparing to that of unfilled blends.