γ-radiation-induced grafting of methyl methacrylate to polypropylene: the effects of water and mineral acid

As part of a program involving the modification of polymers to improve their resistance to photodegradation, we have been investigating simple techniques of grafting various vinyl monomers to polyolefins. In a recent publication, Garnett and Yen reported that improved yields of γ-radiation-induced styrene-grafted polyethylene and polypropylene were obtained if the monomer solution in methanol was acidified with a mineral acid. They attributed the result to an increased hydrogen atom yield when acidified methanol is irradiated. The technique appeared attractive for our purposes because prior removal of oxygen from the solution was not necessary and only low radiation doses were required. This preliminary communication reports the results of some of our investigations into the radiation-induced grafting of methyl methacrylate (MMA) onto polypropylene (PP) film. The results indicate that the presence of water increases the grafting yield significantly, and this effect is associated with the reduced oxygen concentration in the monomer solution