EFFECT OF DOSE-RATE ON RADIATION-INDUCED POLYMERIZATION OF STYRENE ADSORBED ON SILICA-GEL

In the reported experiments, the effect of dose rate on the rate of polymerization and molecular weight distribution of radiation-induced polymerization of styrene adsorbed on silica gel was studied in a wide dose rate range of 4. 4 multiplied by 10**4 to 3 multiplied by 10**8 rad/hr by gamma rays of **6**0Co and electron beams with a Cockroft-Walton-type accelerator. Dose rate dependence on the initial rate of polymerization was about 1 below 3 multiplied by 10**7 rad/hr, and it decreased gradually at high dose rates. Throughout the dose rate range, graft polymerizations and homopolymerizations by cationic and radical mechanisms proceeded simultaneously. Dose rate dependence of the cationic polymerization was 1 below 3 multiplied by 10**7 rad/hr, while dose rate dependence of the radical polymerization was 0. 65 below 3 multiplied by 10**7 rad/hr. At high dose rates, molecular weight and fraction of graft polymer decreased, and fraction of cationic polymerization increased. A very high-molecular-weight graft polymer was formed above 4. 4 multiplied by 10**5 rad/hr at the initial stage of the polymerization.