Behaviour of Elastomeric Seals at Low Temperature

The properties of elastomer 0-ring seals (Viton, silicone rubber, EPDM) at low temperature have been investigated by measuring the gas leakage rate and the sealing force during thermal cycling between + 20°C and -70°C. For all materials it has been found that at a well defined (critical) temperature the leakage rate sharply rises from permeation level to a high value which is determined by gas streaming through the leak path between the 0-ring and the flange surfaces arising from thermal contraction of the elastomer in the glassy state. At the critical temperature the sealing force has been found to be zero or even negative due to adhesion between the elastomer material and the flanges. For all seals the critical temperature is well below the glass transition of the elastomer and also significantly below the temperature where the compression set becomes 100 %. Warming up the sealing system restores leak tightness. Low temperature cycles of elastomeric seals have been found to be entirely reversible.