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An investigation of the efficiency of heat stabilisers Bisphenol-5 and Vulcanox BKF in the production of nitrile butadiene rubber*

The properties of heat stabilisers Bisphenol-5 [4,4′-bis(2,6-di- tert-butylphenol)] and Vulcanox BKF [2,2-methylene-bis(4-methyl-6- tert-butylphenol)] and their efficiency in stabilising nitrile butadiene rubbers (SKN-1865 and SKN-2665) were investigated. The efficiency of the antioxidants was assessed from the thermooxidative ageing of the rubbers at 150°C over the course of 1 and 3 h. The Mooney viscosity and solubility of specimens with Bisphenol-5 change less during oxidation than those of specimens with Vulcanox BKF. The good stability of the Bisphenol-5 dispersion after additional treatment in a ball mill for 12 h was shown. Stability was assessed from the sedimentation rate of antioxidant particles and from the ratio of sediment to dispersion volume. The vulcanisation time and physicomechanical properties of compounds based on rubbers containing Bisphenol-5 and Vulcanox BKF were compared. The recommended content of Bisphenol-5 in SKN-1865 rubber is 0.23 parts, and in SKN-2665 rubber 0.3 parts. Bisphenol 5 can be recommended as a replacement for imported Vulcanox BKF for the stabilisation of nitrile butadiene rubbers.