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 bythermal decomposition of dicumylperoxide (DCP) using supercritical carbon dioxide (scCO2) as a solventand swelling fluid. Provided that the initial concentration of anhydride dissolved in scCO2 is higher than1% w/w, the grafting occurs without significant molecular weight modification of the polymer, and witha proper selection of the operative conditions, a grafting level higher than 0.5% w/w with respect to thepolymer mass was obtained. The amount of grafted MA was determined by FT-IR spectroscopy andpolymer degradation was monitored by dynamic mechanical tests in the melt state. The effect of MA andDCP concentration, of the scCO2 density, and of the reaction time on the grafting yield and on the meltflow behavior was studied. Maleic anhydride homopolymerization during the grafting is suggested byFTIR spectra. The home-synthesized maleated iPP was used as effective compatibilizing agent in thepreparation of iPP/Nylon-6 blends.