Polydimethylsiloxane containing isocyanate group-modified epoxy resin: Curing, characterization, and properties

A synthesized polydimethylsiloxane containing an isocyanate group was used to improve the flexibility and to reduce the internal stress of epoxy resin cured with MDA (4,4'-methylene dianiline). The effect of polysiloxane cont ent on the curing kinetics of a novolac-type epoxy modified with an isocyan ate group was investigated. It was found that the modified epoxy resin show ed significant improvement in impact strength. The polysiloxane containing isocyanate groups effectively depressed the internal stress of cured epoxy resins by reducing the flexural modulus and the coefficient of thermal expa nsion, while the glass transition temperature was increased. (C) 1999 John Wiley & Sons, Inc.