Preparation and properties of thioglycollic acid modified epoxidised natural rubber and its blends with natural rubber

Solution prepared epoxidised natural rubber (ENR) was modified while still in solution with thioglycollic acid (TGA) (0.3 mol phr) to yield a material with 17% conversion of its initial NR epoxide. This material (ENR–TGA) and its blends with natural rubber were black filled and vulcanised using the semi-EV system. The modified ENR material exhibited low tensile strength (4.4 MPa), but showed better resistance to solvent and mineral oil than a similar natural rubber compound. Blending natural rubber with the modified ENR material at a level of 10 parts ENR–TGA phr increased the modulus values by 46%. At the aforementioned blend composition, the hardness and resistance to swelling in solvents and mineral oil were also increased, but the reverse were the case for tensile strength and elongation at break. Cure behaviour and flex-cracking properties of the blends were also studied.