Elastic Recovery of Rubber Vulcanizates at Very Short Times

Abstract

Elastic recovery is a measure of the extent to which a rubber specimen regains its original dimensions after release of an imposed strain. A recoverable strain and rate of recovery after prolonged aging under compression in the environment of intended use are important factors in characterizing rubber performance characteristics. So far the recoverable strain and its rate at very short time intervals have not been studied. Therefore, the present study describes an instrument and reliable method for measuring elastic recovery after release of compressive strain within time periods from 0.007 to 0.1 s. Significant differences are observed in both recoverable strains and their rates measured within these short time periods for the different rubber vulcanizates after aging. Data obtained for various rubbers aged in different environments are fitted to power law and Williams-Watts equations relating elastic strain with time after release of stress. The intercept in the power law equation and characteristic time in Williams-Watts equation are found to be very sensitive to changes in the elastic recovery of various rubbers during aging. The designed testing procedures will make possible the ability to discriminate different rubber materials intended for use in sealing applications, especially those used in dynamic seals. A comparison between novel and traditional measurements is also given.