Elastomers are pleasantly elastic sealants for many applications. They fill out irregularities by mechanical machining or welding and thereby seal leaks. Furthermore, they dampen the predominantly metallic structure of the vacuum chamber and the piping.
However, they also have properties unpopular in vacuum technology. Firstly, the going through of gases, also called permeation, limits the application to leakage rates of approx. 10-9 to 10-10 Pa m3/s.
Secondly the outgassing, which limits the application to vacuum discharge pressures of approx. 10-5 to 10-7 hPa. The outgassing reduces over time and more while heating the equipment.
In addition, elastomers react with gaseous and liquid media and can generate products of decomposition, which can enter the medium of the whole equipment. The seals themselves can lose substance and thereby let the seal become permeable. Elastomers can also corrode the adjacent material. Elastomers are limited temperature resistant.
Therefore several versions of the extremely diverse material elastomer are available for different applications in vacuum technology.