There has been little effort to quantitatively understand the simultaneous graft copolymerization of two monomers in batch and continuous mixers. In this study maleic anhydride/styrene and methyl methacrylate/styrene monomer pairs were grafted onto polypropylene in both an internal mixer and a twin screw extruder. There is little information on the evolution of grafting reactions of dual monomers with respect to time in an internal mixer and along the screw axis in a twin screw extruder The influence of reaction time in an internal mixer and residence time in a twin screw extruder on degree of grafting was measured. The dependence of the degree of grafting with respect to ratio of comonomer concentration was determined. A kinetic scheme was proposed and experimentally tested.