Radiation Processing of Natural Rubber Latex

Abstract

Natural rubber latex (NRL) is the material of choice for the manufacture of products such as gloves, condoms, and balloons owing to its high strength, elasticity, comfort in use, good barrier properties, and “green image.” Natural rubber (NR) gains unique properties by crosslinking reactions which can be achieved in different routes, namely sulfur, peroxide, and radiation vulcanization. Among these vulcanization techniques, sulfur vulcanization provides products with superior tensile strength compared to radiation/peroxide vulcanization. The accelerators used in sulfur cure system may cause potential danger to human health and safety. Radiation vulcanized natural rubber latex (RVNRL) products have many advantages such as the absence of carcinogenic nitrosamines, low cytotoxicity, high transparency, and softness. These properties are achieved by the absence of residual sulfur, zinc oxide, and dithiocarbamates that occur in sulfur vulcanizates. The mechanical properties of both radiation (RVNRL) and peroxide vulcanized natural rubber latex (PVNRL) are low when compared to sulfur pure vulcanized natural rubber latex (SVNRL). Accordingly, radiation-induced peroxide vulcanization (RIPV) was proposed with n-butyl acrylate (n-BA) as a sensitizer and t-butyl hydroperoxide (t-BHPO) as a co-vulcanizing agent. It was found that the addition of t-BHPO is a more practical method to reduce the vulcanization dose required for natural rubber latex. It was also reported that natural rubber nanocomposites produced by blending RVNRL with dispersions of layered silicates showed excellent barrier and aging properties. As the non-rubber constituents and proteins in natural rubber latex are get removed during radiation processing RVNRL films offer excellent transparency which makes the material suitable for the manufacture of baby teats. The addition of water-soluble polymers and the grating of latex with styrene, methyl methacrylate, etc., were explored thoroughly for industrial production in niche areas.