摘要:
Block copolymers are prepared by coupling a poly-.alpha.-methylstyrene block with a polydiorganosiloxane block through a small amount of coupling units of the formula ##STR1## where R denotes an alkyl radical of 1 to 4 carbon atoms. The resulting block copolymers have an improved glass transition temperature, reaching a value of approximately the glass transition temperature of an analogous poly-.alpha.-methylstyrene when R is tertiary-butyl.
摘要:
The impact strength of certain thermoplastic vinylic polymers is improved by polymerizing the corresponding monomers in an emulsion of a diorganosiloxane containing units of the formula HSR'SiR.sub.n O.sub.3-n/2. For example a styrene acrylonitrile copolymer containing 20 percent by weight of a dimethylsiloxane-3-mercaptopropylsiloxane copolymer having 1 mol percent mercaptosiloxane has an Izod notched impact strength of 10.8 foot pounds per inch.