The Cold-Compression sets of Natural and Synthetic Vulcanizates

Abstract

The behavior of certain large synthetic rubber gaskets on naval vessels during the past winter points to the necessity for a cold compression-set test in the specifications for these gaskets. It has been found, for example, that Neoprene gaskets on large valves, which perform satisfactorily at temperatures of 60° F and above, are not usable at temperatures of 40° F and below. They take a cold compression-set, while the valves are closed, so that when the valves are opened and then again closed, the leading edge or surface of the valve does not seat properly. This cold compression-set is not permanent; when the gaskets which exhibit cold compression-set are removed to a warm atmosphere (about 80° F), they slowly regain their original shape. A survey of the literature dealing with the effects of low temperatures on rubber compounds yielded no information on cold compression set. The set test proposed by Morris, James, and Evans in connection with their low temperature stiffness test is not directly applicable to the present problem because it is conducted in tension. Therefore to investigate cold compression-set, it was necessary to devise a new testing procedure.

Elastic recovery after compression in HNBR at low and moderate temperatures: Experiment and modelling

“…The observed set is not permanent. As already noticed by Morris et al [2], putting the cold CS specimens back to the ambient condition leads to relatively quick (10-20 min) restoration of the major portion of their original shapes. More quantitative CS experiments at various temperatures down to -30 °C followed.…”

“…Despite its importance in many practical applications, the elastic recovery or set properties at low temperatures are covered rather scarcely in academic literature. Morris et al [2] reported high compression set values for several rubber systems exposed to cold environment and noticed that the set effect is reversible upon warming to the ambient temperature. Similar effects of low temperatures on the elastic recovery in styrene butadiene rubber (SBR) and nitrile butadiene rubber (NBR) were later described in [3].…”