Peroxidation of Polymethylhydrogensiloxane and Cellulose by [gamma]-Irradiation in Air and Grafting Induced by Their Decomposition

The peroxides of polymethylhydrogensiloxane, cellulose and a mixture of both were determined by ferrous ion method. The relation between the decomposition of the peroxide and the degree of grafting by standing at an elevated temperature after irradiation was examined. The G-value for the peroxide formation of polymethylhydrogensiloxane was found to be 8.7, and the activation energy for the peroxide decomposition was determined from calculation to be 43kcal/mol. The ratio of G-values of silicone between those terminated by methoxy radical and by methyl radical is estimated to be about 2/1. It would thus appear certain that the rate of peroxidation is affected by the end group. The peroxidation is not a chain reaction at room temperature, and the peroxide is produced by the recombination of the peroxy radical. At least two types of peroxide are produced by irradiation in air, and one is decomposed at 80°C but the other is relatively stable. On the other hand, the G-value for the peroxide formation of cellulose is equal to 5.6. The tendency seen for the decrease of the peroxide corresponds to that of increasing degree of grafting, and it may be concluded that only 1/10 of the peroxides formed in the cellulose∼silicone system results in grafting, since it has been calculated that the G-value for the grafting through the peroxide is about 1.0.