EFFECT OF OXYGEN ON INTENSITY EXPONENTS OF RADIATION-INDUCED POLYMERIZATION RATES

Gamma radiation‐induced graft polymerization to natural rubber in benzene solution (solution grafting), graft polymerization to natural rubber latex (Emulsion grafting), and emulsion polymerization of three vinyl monomers—styrene (St), methyl methacrylate (MMA) and acrylonitrile (AN), were carried out under air atmosphere to compare the radiation intensity exponent of each polymerization rate under air atmosphere with that under nitrogen atmosphere or under vacuum. The intensity exponents of the solution grafting both under air atmosphere and under exclusion of air were found to be numerals near one half. This indicates prevailing normal radical mechanism. However, the intensity exponents of the emulsion grafting under air atmosphere were found to be 0.94, 1.00, and 0.82 for St, MMA, and AN, respectively, and those of the emulsion polymerization under air atmosphere, 0.16 and 0.15 for St and MMA, respectively, although those of both emulsion grafting and emulsion polymerization under exclusion of air were found to be numerals near to one half except for that of emulsion polymerization of AN. For emulsion grafting, the initiating species is considered to be trunk polymer radical but the terminating species is assumed to be the radical(s) produced in the water phase in the presence of oxygen. For emulsion polymerization, both initiating and terminating species are assumed to be the radical(s) produced in the water phase in the presence of oxygen. Copyright © 1969 John Wiley & Sons, Inc.