Polypropylene nanocomposites with polymer coated multiwall carbon nanotubes

Abstract Multiwall carbon nanotubes (MWNT) have been functionalized using nitric acid. The functionalized MWNTs (f-MWNT) form stable dispersions in butanol, while as received nanotubes do not. The f-MWNTs/butanol dispersion was added with polypropylene (PP) or maleic anhydride grafted polypropylene (MA-g-PP) in xylene solution to form PP/f-MWNT and MA-g-PP/f-MWNT master batches, respectively. Both PP and MA-g-PP formed coatings on f-MWNTs, where the polymer coating thickness was 4–5 nm. Both PP and MA-g-PP exhibited non-covalently bonded interactions with f-MWNTs, and the evidence of these interactions was obtained using FTIR spectroscopy. The interfacial polymers (PP or MA-g-PP) in the master batches exhibited about 20 °C higher thermal decomposition temperature and greater chemical resistance in xylene than the bulk matrix polymer (PP or MA-g-PP). The PP/f-MWNT and MA-g-PP/f-MWNT master batches, as well as pristine MWNTs (p-MWNT) were melt blended with PP and injection molded nanocomposite samples were prepared from the melt blends. Studies regarding crystallization, rheology, and mechanical behavior all showed distinct differences in the nanocomposites performance when processed with MWNTs via the two master-batch approaches, and from pristine nanotubes. Both master batches resulted in much better MWNT dispersions than was achieved using p-MWNTs. Mechanical properties of the three types of injection molded samples at 0.1 wt% MWNT have been determined and compared.