HMS -H271

HMS -H271 by Gelest (Mitsubishi Chemical) is 25-35% (Methylhydrosiloxane) and 65-70% (dimethylsiloxane) copolymer. Acts as crosslinking agent for vinyl-addition silicones. This hydride functional polymer undergoes three main classes of reactivity: hydrosilylation, dehydrogenative coupling and hydride transfer. It has more readily controlled reactivity than the homopolymers which results in tougher polymers with lower cross-link density. The preferred catalysts for the reactions are platinum complexes such as SIP6830.3 and SIP6832.2. In principle, the reaction of hydride functional siloxanes with vinyl functional siloxanes takes place at 1:1 stoichiometry. HMS -H271 is used in encapsulant applications.