Preparation Of Allyl-Containing Or Epoxy-containing Siloxanes

Introduction of functional groups to polysiloxane chains can receive modified polysiloxane or siloxane copolymer with special properties and applications. Among them, the double bond in vinyl-containing polysiloxane can be croosslinked with hydrogen siloxane or with peroxide, which means it can be used in the preparation of additional silicone rubber and high temperature vulcanization silicone rubber. On the other hand, epoxy-containing siloxane has basic properties of siloxane and the reactivity of epoxy group, which can be reacted with a variety of functional groups so that the siloxane can be further modified and a series of derivatives can be obtained.In this paper, several allyl-containing or epoxy-containing siloxanes or polysiloxanes were synthesized from o-allyl phenol, 1,3-bis(chloromethyl)-1,1,3,3- tetramethyl-disiloxane,γ-chloropropyl methyl dimethoxysilane, epichlorohydrin and hydrosiloxane, and the application properties of the resultants were briefly tested. A series of allyl-containing siloxanes which have potential in application were prepared from 1,3-bis(chloromethyl)-1,1,3,3-tetramethyl-disiloxane,γ-chloropropyl methyl dimethoxysilane, octamethylcyclotetrasiloxane and o-allyl phenol through the Williamson reaction, which include 1,3-bis(o-allyl phenoxymethyl)- 1,1,3,3-tetramethy-disiloxane,α,ω-bis(o-allyl phenoxymethyl)-capped dimethyl siloxane oligomer,γ-(o-allyl phenoxy)-propyl methyl siloxane oligomer andα,ω-bis(o-allyl phenoxymethyl)-cappedγ-(o-allyl phenoxy)-propyl methyl siloxane oligomer. Reaction conditions were optimized, and 1H NMR and IR were applied to characterize the structures of the products.On this basis, formic acid and hydrogen peroxide were used to epoxidizeγ-(o-allyl phenoxy)-propyl methyl siloxane oligomer in situ to get epoxy-containing siloxane. Studies on reaction factors were carried out to get the optimized reaction conditions, in which formic acid/allyl (molar ration) 1.40, hydrogen peroxide/allyl (molar ration) 3.00, the catalyst concentrated sulfuric acid 0.9%(mass ratio), at 65℃for 6 h. Under these conditions, the optimized epoxide value was 0.149.In addition, siloxane with epoxy in the side chain was also be prepared from o-allyl phenyl glycidyl ether and hydrogen siloxane through hydrosilylation reaction with chloroplatinic acid as the catalyst. 1H NMR and IR were applied to characterize the structure of the products. Compared with the previous method, the reaction condition of this way was relatively easy to control and epoxy-containing siloxane could be received with set epoxide value.Curing tests were also carried out in this paper. Allyl-containing polysiloxanes can be crosslinked with hydrogen siloxane with chloroplatinic acid as the catalyst. Thermal analysis indicated that the cured siloxane showed good heat resistance performance in nitrogen atmosphere and air atmosphere, with the initial decomposition temperature above 350℃. Epoxy-containing siloxane received from hydrosilylation was cured with diethylenetriamine or with aminopropyltriethoxysilane, with the initial decomposition temperature above 300℃. Meanwhile, a small amount of this kind of epoxy-containing siloxane could be added to the composition containing epoxy resin and carboxyl-containing siloxane, so that the adhesive properties, flexibility and thermal properties of the cured composition could be improved to a certain extent.