Heretofore, reactive liquid polymer (RLP) epoxy adducts have been used for many years for toughening composites and adhesives. They provide outstanding improvement at room temperature, but are only minimally effective at lower temperatures. An epoxy adduct using CTB can improve low temperature performance, but the CTB, with no or low bound acrylonitrile content, is not miscible in uncured epoxy and will separate upon aging.