Fig. 3-8 Field weathering test: change in tensile strength of conventional and radiation vulcanized rubber films Used rubber products, prepared by conventional and radiation vulcanization, are compared with each other with respect to decomposition rate in the natural environment. The conventionally prepared ones decomposes more slowly. This is due to the dithiocarbamine in the rubber added by conventional methods as a cross-linking promoter and which is known to act as antioxidant for the products and also as poisoning to micro-organisms which degrades used rubber products.

Natural rubber latex (the milky white fluid found in rubber-producing plants containing dispersed particulates of long natural rubber molecules) after treatment with sulfur powder (and dithiocarbamine and zinc oxide) will produce rubber products characterized by high strength and flexibility. However they sometimes become a cause of trouble, as for example when they cause allergic reactions to their users owing to the rubber proteins. Cross-linking of rubber molecules (= vulcanization) can be achieved also by a radiation chemical method. We studied the radiation effect of allergic response and biological adaptability in natural rubber latex as well as changes in the chemical components and molecular weight distribution after irradiation, even from an economical and environmental point of view and thus we proved the advantages of the radiation vulcanization over the conventional one.

Reference K. Makuuchi et al., Allergic Response of Radiation Vulcanized Natural Rubber Latex, Nippon Gomu Kyokai-Shi, 68, 263 (1995).

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