As the accelerating effect of water in the crosslinking reaction of rubber in natural latex by γ-irradiation was assumed to stem from the decomposition of water into radicals by γ-irradiation, more effective reagents were sought among the organic halides which have greater G values for radical formation by γ-irradiation and, simultaneously, an affinity for rubber greater than that of water. 1,2-Dichloroethane, chloroform, carbon tetrachloride, and benzene (for comparison) were tested, and these compounds, except for benzene, were found to accelerate the reaction in proportion to their G values for radical formation. Benzene was found to have no effect, in concentrations between 1 and 5 phr. The optimum dosage was decreased to 2.1 × 106, 1.0 × 106, and 7.6 × 105 r by the addition of 1, 3, and 5 phr of carbon tetrachloride, respectively, and was assumed to have decreased to 1.17 × 107, 9.0 × 106, and 7.6 × 106 r with 1, 3, and 5 phr of 1,2-dichloroethane, and to 8.6 × 106, 6.2 × 106, and 5.2 × 106 r with 1, 3, and 5 phr of chloroform, respectively. The physical properties of the films obtained at the optimum dosages under these accelerating conditions were equal to those of the latex irradiated up to the optimum dosage with no addition of halide. No side reactions occurred during the halide-accelerated crosslinking that were sufficiently extensive to influence the infrared spectra.
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