Significance and Test Method
Compression set at low temperatures is simply the acid test for sealing materials. What is left of the material’s resilience in the cold?
At low temperatures, rubber materials continuously lose their elasticity. As a result, they can only recover and bridge gaps to a limited extent and their resetting rate slows down considerably.
The determination of the compression set at low temperatures provides information about the behaviour of the materials during cooling and the retention of their rubber elasticity
Significance for Application Technology
Not only for seals, but for all components whose function depends on the elasticity of the material, the compression set at low temperatures is a reliable measure of how well an elastomer material performs in low-temperature applications.
For typical static O-ring applications, it we can assume that O-rings will only leak above a compression set value of 90 to 100 %. However, some standards (DIN EN 549), however, define the functional criterion much more strictly.
The Compression Set Test at low Temperatures
(DIN) ISO 815-2 describes test procedures for determining the compression set at low temperatures. Basically, the test is similar to a compression set test at ambient or elevated temperature. The difference is that the loaded sample is not heated but cooled down and the relaxation time before measuring is longer.
Since, due to the low temperatures, the resetting of the sample is much slower than at high temperatures, it may not be completed after 30 minutes. Therefore, the DIN ISO 815-2 or ISO 815-2 standard also provides for a method with measurements up to 2 hours after relaxation.
