Effects of epoxy content on dynamic mechanical behaviour of PEI-toughened dicyanate–novolac epoxy blends

By varying the cyanate/epoxy ratio, three polyetherimide(PEI)‐modified bisphenol A dicyanate–novolac epoxy resin blends with different epoxy contents were prepared. The effects of epoxy content on the dynamic mechanical behaviour of those blends were investigated by dynamic mechanical thermal analysis. The results showed that the glass transition temperature of the cyanate–epoxy network ( T g1 ) in the modified blend decreases with epoxy content. When the epoxy content increases, both the width of the glass transition of the cyanate–epoxy network and its peak density are depressed substantially. Although the tangent delta peak value of PEI is basically independent of epoxy content, the T g of PEI ( T g2 ) decreases with epoxy content. T g1 is independent of the PEI loading. When T g1 is lower than T g2 , however, the T g1 in the blend with revised phase structure is substantially lower than other blends. Copyright © 2004 Society of Chemical Industry