Kinetics of diffusion‐free radiation graft polymerization of styrene onto polyethylene

The diffusion‐free radiation graft polymerization of styrene onto polyethylene has been studied. The grafting rate shows a dependence on monomer which is far different than what has been assumed. Further, the dependence on monomer changes with increasing dose rate as does the dependence of grafting rate on radiation dose rate. Three different regions of behavior are defined: (1) a region of low dose rate where the grafting rate is 1/2‐order in dose rate and 3/2‐order in monomer; (2) a region of intermediate dose rate where the grafting rate is intermediate between 1/2‐and zero‐order in dose rate and 5/2‐order in monomer; and (3) a region of high dose rate, where the grafting rate is independent of dose rate and at least 5/2‐order in monomer. Various possible mechanisms responsible for these effects are discussed, including the effects of viscosity on the initiation and termination reactions, the possibility of ionic graft polymerization, and energy transfer.