Degradation of vulcanized natural rubber using locally available natural oils

Abstract

Rubber products used in many industrial and domestic applications are discarded after long term usage. Due to crosslinked structure of rubbers and the presence of stabilizers and other additives, very long times are needed for natural degradation causing an environmental problem. Recycling, reusing and making degradable polymers are the solutions to this environmental issue. Rubber molecules are susceptible to degradation in the presence of peroxide radicals. Oxidation of natural oils can produce peroxide radicals and the rate of oxidation increases with the degree of unsaturation. Therefore, highly unsaturated locally available soybean and sesame oil were used for the study. Vulcanized rubber samples were prepared according to the tire tread formulation. Rubber samples were immersed in either sesame oil or soybean oil separately, for various time periods at room temperature and the degradation behavior was monitored by using mechanical properties (tensile and tear strength) and degradation temperature. Simultaneously, degradation behavior of rubber samples in both oil types were studied, in the presence of Cu catalyst and sunlight. Longer the time immersed in oils, lower the tensile strength, tear strength and degradation temperature of vulcanized rubber samples indicating improved degradability. In addition, the presence of sunlight and copper catalyst each has enhanced the reduction of above properties within a short time period. From the two types of oils used, soybean oil was the best. The enhanced degradation will provide a solution for environmental problems caused due to non-degradable rubber waste.