Bismaleimides (N,N′-bismaleimide-4,4′diphenylmethane and N,N′-bismaleimideo-4,4′diphenylsulphone) modified bisphenoldicyanate-epoxy matrices for engineering applications

An interpenetrating network of cyanate ester (CE)-bismaleimide (BMI)-epoxy matrix systems was developed. Epoxy systems modified with 4%, 8%, and 12% (by wt) of cyanate ester were made by using epoxy resin and cyanate ester with diaminodiphenylmethane as curing agent. The cyanate-ester-toughened epoxy systems were further modified with 4%, 8%, and 12% (by wt) of bismaleimides, namely N,N'-bismaleimido-4,4'-diphenylmethane and N,N'-bismaleimido-4,4'-diphenylsulphone. BMI-CE-Epoxy matrices were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and heat deflection temperature (HDT) analysis. The DSC thermograms of cyanate-ester-modified epoxy and BMI-modified epoxy during cure show unimodal reaction exotherms. The studies indicate that thermal stability and resistance to water absorption of epoxy resin has been enhanced by the introduction of cyanate ester. The incorporation of bismaleimide into unmodified epoxy and CE epoxy enhanced the thermal and mechanical properties according to its percentage content. The morphologies of fractured surfaces of modified epoxy systems were compared with the unmodified epoxy system.