Rheology and Morphology of Polypropylene In Situ Grafted and Blended With Methyl Methacrylate/n-Buthylacrylate Copolymer

The rheology and morphology of polypropylene (PP) modified by grafting and blending with vinyl monomers were studied in this work. The PP powder was impregnated by mixture of methyl methacrylate (MMA)/n-buthylacrylate (n-BA) and copolymerized with azobisisobutyronitrile (AIBN) initiator. The simultaneous grafting and blending of PP with MMA-co-n-BA copolymers were performed in a corotating, 40 L/D, twin-screw extruder in the presence of dicumyl peroxide. The Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were used to verify the grafting level and dispersion state of MMA/n-BA copolymer on PP matrix, respectively, and their rheological properties were studied. It is observed that MMA/n-BA copolymer is finely dispersed in the PP matrix. In this way, PP can be grafted, blended, and simultaneously compatibilized with polar copolymers, as is seen in SEM images. The results showed that by increasing acrylate monomers grafting on to PP increased. The same trend was observed for AIBN initiator. The gel content of samples with 25% monomers showed an increased from 0.7% to 3.5% by increasing AIBN from 0.2% to 0.4%. The grafting reaction took place with chain scission of PP molecules and also cross-linking reactions. The optimum grafting of 7.3% with lowest chain scission and cross-linking were obtained for samples containing 15 wt% monomer and 0.3% AIBN initiator. (C) 2014 Society of Plastics Engineers