Question: How is compression testing done for liquid silicone?
Answer: Compression set measures the permanent deformation of parts that have been subjected to high temperatures for some predetermined amount of time. One standard for compression set used in supplier literature is ASTM D395 A or B. Basically a standard puck is compressed between two plates and subjected to temperatures in the range of 250F at constant force or constant deflection. The sample is allowed to recover for 30 minutes and then measurements are taken. Alternative tests like ISO 815-B heat for 22 hours at 175 degrees C. The test method dictates the calculation but basically the compression set is a measurement of how well the puck returns to the initial thickness, so lower values indicate higher resistance to permanent deformation.