Swelling of Synthetic Rubbers in Mineral Oils. Swelling in Mineral Oils Containing Polyolefins and in Mixtures of Nujol and Biphenyl

Abstract

Abstract The true cloud temperature of a 50–50 weight mixture of aniline and mineral oil is a reliable index of the amount of swelling a synthetic rubber undergoes when immersed in mineral oil. This result is also true of mineral oils which contain polyolefins. Since the presence of both haze and cloud points is characteristic of such oils when mixed with aniline, a method has been worked out for distinguishing between them. Conversely, the presence of both haze and cloud points is believed to be indicative of the fact that polyolefins have been added to the mineral oils. The addition of polyolefins to mineral oils reduces the tendency of those oils to swell synthetic rubbers. The logarithm of the percentage swelling varies inversely with the aniline point. Although mixtures of Nujol and biphenyl can be duplicated fairly well, they offer no advantage over mineral oils for testing the tendency of synthetic rubber compositions to swell. Although the logarithm of swelling decreases as the 50 per cent aniline of the mixture increases, the relationship is not the same as that found for mineral oils. for evaluating behavior under service conditions, immersion tests in oils having the same aniline point as oils which may be encountered in service are believed to be more reliable and more significant.