The application of nano silica as a potential, cost-efficient green filler in acrylonitrile butadiene rubber vulcanizates containing carboxy-terminated liquid natural rubber

Abstract

The challenge of sustainable development demands renewable natural sources. Natural rubber is one of the major plantation crops in the equatorial region, where there is a tremendous scope for tapping solar energy. The carboxy-terminated liquid natural rubber (CTNR) was commercially prepared by the sunlight irradiation of a solution of maleic anhydride and masticated natural rubber. Carboxy-terminated liquid natural rubber (CTNR) can be used as a polymeric plasticizer in acrylonitrile butadiene rubber (NBR) vulcanizates. As a reinforcing filler in rubber products, bio compatible green silica is rapidly replacing carcinogenic carbon black. This paper describes the cost-effective application of eco-friendly nano silica, which can improve the tensile properties, rebound resilience, compression set, ageing and oil resistance and reduce the heat build-up of the NBR vulcanizates. The properties of nano silica–filled NBR vulcanizates containing CTNR (NS NBR -CTNR) were compared with those containing amorphous silica. The enhancement in properties, exhibited by NS NBR-CTNR vulcanizates, may be attributed to the increased bound rubber content resulting from the large surface area of the nano-sized filler. The superior retention of properties after ageing and oil extraction shown by NS NBR-CTNR vulcanizates may be due to the better rubber filler interaction, ionic crosslinking and co–cross-linking of CTNR to NBR. The use of a combination of a conventional plasticizer and CTNR in nano silica–filled NBR is found to be promising.