RUBBER COMPOSITION AND SEALING MATERIAL FOR PLASMA TREATMENT DEVICE

A rubber composition which comprise (a) a cross linkable fluoro elastomer, (b) a reactive fluorine-containing compound (except the cross linkable fluoro elastomer (a)) having a divalent perfluoropolyether structure or divalent perfluoroalkylene structure and containing, in the terminal or a side chain thereof, two or more of alkenyl groups capable of conducting an addition reaction at least with a hydroxyl group in the following organosilicon compound (c), and (c) a reactive organosilicon compound having two or more of hydroxyl groups in the molecule thereof and being capable of conducting an addition reaction with an alkenyl group in the above compound (b), in such amounts wherein the total amount of (b) and (c) is 1 to 10 parts by weight relative to 100 parts by weight of said rubber (a), and further comprises a vulcanizing agent and optionally a crosslinking agent; and a sealing agent for a plasma treatment device, which is produced by subjecting said composition to the primary vulcanization and forming, and then subjecting unreached components in the resultant formed article to the secondary vulcanization in a vacuum oven, to thereby reduce the amount of a gas which is an unreacted component and may be discharged. The above sealing agent for a plasma treatment device is less prone to cause the tackiness or adhesion onto a counter face, is free from the problem of generation of particles and from the contamination by a discharged gas, even in the case of continuous use for a long period of time at a high temperature, in particular, in a semiconductor manufacturing process or the like, and can be produced at a low cost.