| 摘要 |
A composition curable at room temperature comprising an organopolysiloxane having terminal groups consisting of -OH or radicals hydrolysable by ambient moisture and with an organic chain grafted to it. The organo-portion of the organopolysiloxane may comprise methyl groups, other low m.w. alkyl groups and up to 25% of aryl groups. The chain length of the siloxane should give degree of polymerisation 100-1,000 and an equivalent viscosity 100-30,000 cp. The organic monomer may be 25-75%, preferably 40-65% of the reaction mixture. Suitable monomers include vinyl chloride, vinyl esters, styrene, acrylic acids etc. Styrene and butyl acrylate in combination give excellent properties. A cross-linking agent such as ethyl silicate and a catalyst such as dibutyl tinbutoxychloride may be used. When the compositions contain radicals hydrolysable by ambient moisture these are derived subsequent to grafting by reaction of the siloxane of formula XSiY3 where X is an inert group and Y acyloxy, oximo, dialkylaminooxy etc., particularly methyltriacetoxysilane. Room temperature curing compositions of improved strength which can be used in the unreinforced condition. |
