modified polymers , particularly polyolefins with improved flow over that of polyolefin alone , are produced by reacting polypropylene , maleic anhydride monomer , and a peroxy initiator in a twin - screw extruder . the maleic anhydride monomer is injected as a fluid and is grafted onto the base polypropylene during the degradation / chain scissioning process . novel , highly - grafted polymers with high melt flow and other useful properties are produced in pellet form .