Maleic anhydride grafting of polypropylene: peroxide and solvent effects

The grafting of polyolefins with maleic anhydride (MA) has been incorporated into industrial practice to generate copolymers that can act as coupling agents between the non-polar polyolefins and different polar fillers and reinforcements. In the present study, two different peroxides were used to initiate the MA grafting onto polypropylene (PP), namely dicumyl peroxide (DCP) and 1,3-bis (terbutylisopropyl peroxi)benzene (DIBP). The use of DIBP allowed similar grafting yields to DCP to be obtained, but with less chain scission of the polyolefin. Moreover, the utilisation of a coagent, toluene (Tol), leads to a reduction in the chain scission of PP. A monotonous decrease in the melt flow index (MFI) of the polymer was observed with increasing molar ratio of Tol/MA, in the range of ratios considered (0-2(.)5). In addition, the free radical grafting of MA onto PP remained high and optimum grafting was obtained for a molar ratio Tol/MA of similar to 0-5. It was observed that the addition of toluene was effective, independent of the reaction process utilised, namely batch mixing or extrusion.