Siloxane Modifiers for Epoxy Resins.

Abstract : Functionally terminated polydimethylsiloxane and its statistical copolymers with either methyltrifluoropropyl (TFP) or diphenyl siloxane have been used to chemically modify bisphenol A-based epoxy resins. Increasing the percentage of TFP or diphenyl units relative to the dimethyl siloxane content of the oligomers enhanced their compatibility with the epoxy resin. This in turn produced smaller rubber particle sizes and altered particle morphology. Improved fracture toughness relative to the cycloaliphatic diamine-cured control resin was achieved in resins modified with polysiloxane copolymers containing 40% or more TFP content or 20% diphenyl siloxane. Comparisons in these and other aspects are made with similarly prepared ATBN- and CTBN-modified epoxies. Wear rate was quite dramatically reduced with some of the modifiers. Wear results are discussed in terms of the fatigue wear theory.