The final requirement for effective vacuum sealing involves the specification of o-ring elastomers with good compression set characteristics. Employing a seal squeeze of up to 40% inhibits media flow through the seal. This squeeze also forces the o-ring to conform to the surface irregularities of the gland, helping to further prevent leakage. Keep in mind, however, that because of the decreased groove depth, increased groove width is essential.
In terms of compression set resistance, Fluorocarbon Silicone (Fluorosilicone) exhibits excellent compression set at high temperatures. Compression set is a factor of temperature and time, and most compounds work best in room temperature applications.