Maleic anhydride was chemically attached to depolymerized natural rubber, and the product was named as carboxy-terminated liquid natural rubber (CTNR). The CTNR can act as a potential plasticizer in chloroprene (CR) vulcanizates. This paper describes the use of commercial nano silica (NS) as a promising cost-effective filler, which can enhance the tensile properties and ageing resistance of the CR vulcanizates incorporated with CTNR (CR-CTNR). The enhancement in properties may be attributed to the increased bound-rubber content owing to the large surface area of the nano-sized filler. The characteristics of the NS-filled CR vulcanizates containing CTNR (NS CR-CTNR) were compared with those containing amorphous silica. The NS CR-CTNR vulcanizates showed superior ageing and oil resistance due to the finer rubber filler interaction modified by ionic cross linking.
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.
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