Effects of Oxygen Exposure on Plasma Graft Polymerization of Some Hydrophilic Monomers onto Polypropylene Films

Graft polymerization of hydrophilic monomers was made onto O2-exposed polypropylene films that had been previously treated by glow discharge plasma of Ar, and the influence of oxidation on the grafting was investigated. The grafting yield decreased with an increase of O2 exposure time (∼ 1000 minutes) when the reaction occurred at 60°C. The yield was very dependent on the reaction temperature, and the temperature for maximal grafting amounts of 2-hydroxyethyl methacrylate onto oxidized films was shifted to around 75°C. It was believed that the dissociation of peroxide group on substrate films took place effectively near this temperature. The oxidized substrates were also activated when the reaction was carried out in the presence of metal ions in their reduced state (e.g., Fe2+). The generated oxiradicals should participate effectively in the initiation of graft polymerization.