Influence of •OH radicals on the radiation effect of polydimethylsiloxane latex

Abstract

By measuring the gel fraction and GPC spectra of irradiated polydimethylsiloxane (PDMS) samples, the radiation effect of PDMS in latex form was investigated. Results showed that the •OH radical could not only initiate the radiation crosslinking of PDMS latex, but also accelerate the scission of PDMS molecular chain. For the PDMS latex without additives, the effect of •OH on the crosslinking behavior is not obvious. However, the addition of H2O2 or KIO4 or N 2O which could increase the concentration of •OH would enhance the radiation degradation of PDMS. Moreover, with the increase of absorbed dose, the degradation is more predominant to lead to the drop of gel fraction. Particularly, in the presence of crosslinking sensitizer-trimethylol propane trimethacrylate (TMPTMA), when the dose was above 40 kGy, the excess •OH radical accelerated remarkably the degradation of PDMS chain which resulted in the narrow polydispersity of molecular weight and increase in content of PDMS with low molecular weight, and decrease of gel fraction, comparing with those of irradiated PDMS latex without TMPTMA. This suggested that the synergetic interaction perhaps existed between TMPTMA and excess •OH radical. This might be attributed to that the •OH radicals react with TMPTMA firstly, the resulted product might accelerate the degradation of PDMS.