Properties and crystallization of maleated polypropylene/graphite flake nanocomposites

Abstract

Polypropylene (PP)/graphite (G) hybrid nanocomposites have been prepared by melt mixing using maleated PP (PP-g-MA) and graphite oxide (GO) as compatibilizing agents. Melt mixing was achieved using a Gelitnat, a high-speed thermo-kinetic mixer. The PP-g-MA and GO used as compatibilizers helped the dispersion of the graphite on a nano-scale and improved flexural properties but more significantly the impact strength of the material. TEM micrographs showed a partial exfoliation of the graphite in the PP/PP-g-MA/GO/G hybrid nanocomposites. SEM micrographs of etched nanocomposite samples showed a fine grain micron-sized structure, while pure PP was characterized by larger 3-dimensional spherulites. Non-isothermal crystallization kinetics of PP and PP/PP-g-MA/ GO/G nanocomposites were investigated by differential scanning calorimetry (DSC). The crystallinity and crystallization temperature of the nanocomposites were higher than for neat PP. Using the Kissinger model, the activation energy of crystallization of the nanocomposites was determined to be lower than PP. Models by Ozawa and Liu et al. were used to analyze and describe the non-isothermal crystallization kinetics. Overall, results indicate that the type of nucleation, growth and geometry of PP crystals markedly change in the presence of nano-sized graphite particles. © 2006 The Society of Polymer Science.