Retraction Test for Serviceability of Elastomers at Low Temperatures

Abstract

Elastomer vulcanizates progressively stiffen as the temperature is lowered. Additional stiffening, due to crystallization, may occur as exposure to low temperatures is prolonged. The available methods of testing the low temperature flexibility of rubber and rubberlike materials do not reveal the losses in flexibility caused by crystallization except by using prolonged storage at low temperatures. A retraction test employing large deformations, which greatly increases the rate of crystallization, has been developed. This test rapidly gives a temperature index correlating with the stiffness of elastomer vulcanizates after storage at low temperatures, and can be used to measure the merit for low temperature applications of both crystallizable and noncrystallizable elastomers. This test in conjunction with conventional (room temperature) tests has been used successfully to study the low temperature performance of Hevea, GR-S, Paracril, and polybutadiene vulcanizates along with vulcanizates of many experimental elastomers. Correlation of results with cold compression set and hardness after low temperature storage has been excellent and substantiates the usefulness of the test.