Effects of radiation on oxidation scission of polypropylene powder

Radiation oxidation of polypropylene (PP) and PP with 2% crosslinking agent triallyl isocyanurate (TAIC) (J-PP) powders (the size of the powder particles was approximately 48 μm) were investigated under gamma-ray and electron beam irradiation in air at room temperature (25 ℃). Electron spin resonance (ESR), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and gel permeation chromatography (GPC) were used to characterize the free-radical concentration, chemical structure, thermal stability, and oxidation scission induced by gamma-ray or electron beam irradiation, and the effects of the absorbed dose and dose rate on the properties of PP were also studied. The results showed that peroxy radicals and oxidative products were formed upon irradiation for both PP and J-PP powders, and the addition of the crosslinking agent TAIC could not prevent the degradation of polypropylene. The melt flow index (MFI) and GPC results revealed that the average molecular weight of the irradiated PP and J-PP powders declined with the increasing absorbed doses. (authors)