MECHANICAL PROPERTIES OF NATURAL RUBBER / POLY BUTADIENE RUBBER BLENDS PREPARED USING FATTY ACID INCORPORATED NATURAL RUBBER

摘要

Natural rubber(NR) can be sensitized for quick coagulation by addition of suitable fatty acid salts as stabilizers. A portion of the fatty acids formed remains on rubber after coagulation fatty acids play a major role on cure characteristics and mechanical properties of recovered rubber. Use of this rubber in blends with polybutadiene rubber (BR) can alleviate some of the problems of rubber blends like cure mismatch and unequal filler distribution. In this paper an investigation on the preparation, cure characteristics and mechanical properties of NR/BR blends prepared using fatty acid incorporated NR is carried out. Natural rubber latex is treated with a required quantity of fatty acid soap and then coagulated by addition of suitable acids. The coagulum is washed well to remove acids and then dried at 70 °C in an air oven to get dry rubber. Rubber compounds based on pure NR, 80/20 and 60/ 40 NR/BR blends are prepared using conventional mixing methods. The compounds are vulcanized and tested as per standard test methods. The fatty acid soaps added to latex get adsorbed or rubber particles and get converted to the corresponding fatty acids by reaction with acids during the process of coagulation. Due to presence of fatty acids, the pure and NR/BR blends show better cure characteristics as revealed from a higher level of vulcanization. Due to the higher level of crosslinking and better filler dispersion, pure and blend vulcanizates show a higher modulus, tensile strength, and hardness along with comparable dynamic properties like heat build-up and compression set in relation to conventional rubber vulcanizates. The presence of fatty acids also helps in a better dispersion of filler in pure rubbers as revealed from scanning electron microscopy (SEM) studies. A noticeably higher ageing resistance is also observed for NR/BR blends prepared by the new process due to the presence of better interaction of filler with rubber.