The effects of the molecular weight of polypropylene, nucleating agent, and types of stabilizers on the grafting of methylmethacrylate onto polypropylene sheets were examined. The oxidation of polypropylene sheet surfaces exposed to air after irradiation was studied by measuring survey scan spectra with an X-ray photoelectron spectrometer (XPS). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) technique was utilized to evaluate the concentration of peroxide formed on the irradiated polypropylene sheet by counting the quantity of DPPH consumed by the reaction of peroxide radicals with DPPH. Plastics stabilizers caused a decrease in the concentration of peroxide in the polymer as well as trapped radicals. It was shown that the stabilizer in polypropylene markedly decreased the grafting of methylmethacrylate onto polypropylene.