High strength silicone-urethane copolymers: synthesis and properties

Abstract

High molecular weight silicone-urethane segmented copolymers were synthesized by the reaction of 4,4'-isocyanatocyclohexylmethane (HMDI), α,ω-hydroxyhexyl terminated polydimethylsiloxane olígomers (PDMS) and 1,4-butanediol (BD). Reactions were conducted in two steps in tetrahydrofuran/dimethylformamide solvent mixture under the catalytic action of dibutyltindilaurate. PDMS oligomers with molecular weights of 900 and 2300 g/mole were used during the synthesis. Hard segment contents of the copolymers were varied between 23 and 50% by weight. Thermal (DSC) and thermomechanical (DMTA) characterization of the copolymers showed the formation of two-phase morphologies. Mechanical strengths of these silicone-urethanes were superior to those of conventional polyether based polyurethanes with similar structures and hard/soft segment compositions.