Compression set

The compression set (ASTM D395, ISO 815, …) of a material is the permanent deformation remaining after removal of a force that was applied to it. Compression set is normally measured in two ways: compression set
A – constant force and compression set
B – constant displacement.

Compression Set test is intended to measure the ability of rubber compounds to retain elastic properties after prolonged action of known compressive stress under static loading.

Measuring formula – The compression set A is given by CA = [(to – ti) / to] * 100 where to is the original specimen thickness and ti is the specimen thickness after testing.