Morphology and properties of functionalised MWNT/polypropylene composites

Multiwalled carbon nanotubes (MWNTs) were oxidised via a chemical oxidation process and grafted by the reaction of 1-bromohexadecane with the carboxyl groups bound to oxidised MWNT surface. The composites of polypropylene (PP) with modified MWNTs were prepared by solution blending method. The effects of the dispersion state of MWNTs on the rheological, mechanical and thermal conductive properties of PP/MWNT composites were investigated by comparing oxidised MWNTs and grafted MWNTs (g-MWNTs) incorporated composites. After grafting with long alkyl chains, the dispersion of g-MWNTs in the PP matrix was improved, and they could be homogeneously dispersed at nanoscale. At g-MWNT loadings higher than 3.0 wt-%, the PP/g-MWNT composites exhibited rheological percolation threshold at low frequencies. With the increase in MWNT content, the tensile yield strength of the PP/oxidised MWNT composites was decreased, while that of the PP/g-MWNT composites was increased. The thermal conductivity of the PP/MWNT composites increased with increasing MWNT content.