Grafting of Maleic Anhydride onto Isotactic Polypropylene in the Presence of Supercritical Carbon Dioxide as a Solvent and Swelling Fluid

Grafting of maleic anhydride (MA) onto isotactic polypropylene (iPP) was carried out by thermal decomposition of dicumylperoxide (DCP) using supercritical carbon dioxide (scCO 2 ) as a solvent and swelling fluid. Provided that the initial concentration of anhydride dissolved in scCO 2 is higher than 1% w/w, the grafting occurs without significant molecular weight modification of the polymer, and with a proper selection of the operative conditions, a grafting level higher than 0.5% w/w with respect to the polymer mass was obtained. The amount of grafted MA was determined by FT-IR spectroscopy and polymer degradation was monitored by dynamic mechanical tests in the melt state. The effect of MA and DCP concentration, of the scCO 2 density, and of the reaction time on the grafting yield and on the melt flow behavior was studied. Maleic anhydride homopolymerization during the grafting is suggested by FTIR spectra. The home-synthesized maleated iPP was used as effective compatibilizing agent in the preparation of iPP/Nylon-6 blends.