The Influence of the Rubber Mix Composition on the Ageing Resistance of Vulcanisates Based on Nitrile Butadiene Rubbers of Different Polarity

We studied the influence of the composition of rubber mixes based on nitrile butadiene rubbers of different polarity (BNKS-18, BNKS-28, BNKS-40) on the physicomechanical and relaxation properties of vulcanisates produced using sulphur and peroxide vulcanising systems under conditions of oxidation in an oxygen atmosphere and heat ageing. By electron spin resonance (ESR) spectroscopy it was established that the values of the correlation time before and after the oxidation of vulcanisates based on BNK-28 nitrile butadiene rubber hardly differ from one another, which is indirect evidence of the absence of degradation. The introduction of a vulcanising system and the process of vulcanisation itself activate the oxidation of specimens, increasing the oxidation rate and the amount of bound oxygen. The replacement of the sulphur-containing vulcanising system with a peroxide system increases the induction period of oxidation by a factor of 6–7. The introduction of nanosized titanium dioxide (NTD) (Degussa) into the rubber mix leads to a certain reduction in tensile strength and elongation at break. The addition of 1% NTD into the pure rubber hardly affects the kinetics of oxidation. The introduction of 3% NTD leads to a reduction in the correlation time after oxidation (from 19 × 10−10 to 16 × 10−10 s).