A silicone sheet was dipped into n-butyl methacrylate, monomer including benzoyl peroxide and was swollen for 0.5 h at 23degreesC. Then, the sheet was put into a glass tube equipped with a three-way stopcock and was deoxygenated by freezing under dry nitrogen. Polymerization was carried out by heating at 80degreesC for 2 h under dry nitrogen. The resultant sheet was a component gradient silicone sheet with poly-n-butylmethacrylate. The content of poly-n-butylmethacrylate increased gradually from either surface to the middle of the sheet. This phenomenon was assumed to occur because of the volatilization of n-butyl methacrylate monomer during the polymerization. The properties of the sheet include increased tear strength and decreased gas permeability.