Development of rubbery materials with excellent barrier properties to H2, D2, and T2

Abstract Various acrylonitrile-butadiene copolymers, known as NBR, are known to have much lower gas permeabilities than other rubbers. The purpose of this study is to prepare chemically modified NBR membranes having even lower tritium permeability than unmodified NBR, combined with good antiradiation properties. NBR 41, an acrylonitrile-butadiene copolymer in which the content of acrylonitrile is 41 mol%, was used. Bromination of the NBR 41, to give Br-NBR-41, was carried out by immersing an NBR 41 membrane in saturated bromine water at 20°C and irradiating with a low pressure mercury UV lamp. Membranes of a polymer blend of NBR 41 with poly(vinyl chloride)-N,N-dimethyldithiocarbamate, or PDM, known as Blend-NBR-41, were prepared. PDM was synthesized by the reaction of poly(vinyl chloride) with sodium N,N-dimethyldithiocarbamate. The bromination of Blend-NBR-41, to give Br-Blend-NBR-41, was carried out by the technique used for preparation of the Br-NBR-41 membranes. Temperature dependence of the apparent permeability of NBR-41, Blend-NBR-41 and Br-Blend-NBR-41 to H2, D2 and He was studied. These modified NBR membranes showed excellent barrier properties for H2, D2 and He over a wide range of temperatures. The permeability of T2 through the Br-Blend-NBR-41 membrane at room temperature was about 6% lower than that of H2. The gas evolution from NBR-41 on gamma-ray irradiation was compared with that from the modified NBR-41. The small amount of gaseous products from the modified NBR-41 suggests that this material has excellent antiradiation properties.