This test method assesses the force decay upon rubber in various conditions, both physical and chemical. Also known as compression set relaxation, this standard covers two differing methods for determining the decrease in counterforce exerted by a test specimen of thermoplastic elastomer or vulcanized rubber which has been compressed under controlled conditions at a constant deformation. This method covers testing in both air and liquids.
When rubber undergoes a constant strain, the force needed to maintain that strain decreases over time. Either physical or chemical processes may be responsible for this force decay; at low temperatures and/or short times, force decay is dominated by physical processes whereas at high temperatures and/or long times, chemical processes dominate. It is not safe to extrapolate force decay curves in order to predict ongoing trends in stress relaxation, nor use tests at high temperatures in lieu of accelerated tests for force decay at lower temperatures.
Types of products / materials generally tested under this method
This test is commonly used to determine service life for seals and gaskets.
*Please Note: The information outlined above is to be used as reference for ASTM D6147 Standard Test Method for Vulcanized Rubber and Thermoplastic Elastomer—Determination of Force Decay (Stress Relaxation) in Compression and ISO 3384 Rubber, vulcanized or thermoplastic -- Determination of stress relaxation in compression -- Part 1: Testing at constant temperature. Please refer to the appropriate standards agency for full details and the most current revision.