Our laboratory carries out measurements Compression Set, according to DIN 53517, each batch of material before they are resolved to produce. The Compression Set is a measure of permanent deformation remaining after the material was subjected to a compressive load. It is calculated as the percentage of residual deformation in relation to deformation applied (generally 25% of the original size):

• after a certain period (24 or 70 hours)
• at a given temperature (70 or 100° C)

A low rating is desirable for dynamic seals, where recovery is important. Compression set is significant in that because most seals are loaded in compression some permanent reduction in dimension or shrinkage will occur, by the amount of set characteristic for that material.

This may, however, be offset by other factors, such as swelling of the seal in contact with the fluid or can be allowed for in seal design.