ELASTIC RECOVERY OF RUBBER VULCANIZATES AT VERY SHORT TIMER

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 c ompression in the environment of intended use are important factors in characterizing rubber performance characteristics. So far the recover able strain and its rate at very short time intervals have not been st udied. Therefore, the present study describes an instrument and reliab le method for measuring elastic recovery after release of compressive strain within time periods from 0.007 to 0.1 s. Significant difference s are observed in both recoverable strains and their rates measured wi thin these short time periods for the different rubber vulcanizates af ter aging. Data obtained for various rubbers aged in different environ ments are fitted to power law and Williams-Watts equations relating el astic strain with time after release of stress. The intercept in the p ower law equation and characteristic time in Williams-Watts equation a re found to be very sensitive to changes in the elastic recovery of va rious rubbers during aging. The designed testing procedures will make possible the ability to discriminate different rubber materials intend ed for use in sealing applications, especially those used in dynamic s eals. A comparison between novel and traditional measurements is also given.