Most rubber compounds contain small quantities of oil and other ingredients that will become volatile under vacuum conditions. Evidence of this “outgassing” is apparent as a thin film deposited on surrounding surfaces. Optical and electrical contact applications are of special concern in this situation as they incorporate sensitive surfaces that must remain uncontaminated. Other compounds exhibit some degree of weight loss in the form of water vapor which may act as a contaminant in some applications. While this process is inevitable, it is accelerated at elevated temperatures and in high vacuum situations.
“Post curing” elastomeric compounds such as Viton™, Fluorosilicone, and Silicone prior to service removes many of the unwanted volatiles and improves physical properties by increasing the degree of crosslinking. Other compounds, such as Nitrile and natural rubber, do not usually benefit as much from this process as the previous compounds.