Studies on blends of epoxy-functionalized hyperbranched polymer and epoxy resin

An epoxy-functionalized hyperbranched polymer (HBP) was used to toughen a conventional epoxy resin, diglycidyl ether of bisphenol A (DGEBA) cured with diethyltoluene-2,6-diamine (DETDA). There was little change in gel time as a result of addition of HBP, even though the HBP reacts at a slower rate with amine hardeners compared to DGEBA alone. Phase separation was investigated for various HBP contents and as a function of cure conditions as well. The thermal and dynamic viscoelastic behavior of the modified matrices have been examined and compared to the DGEBA epoxy matrix. It appears that the HBP which phase separates does not react as fully as when it is reacted with the amine alone. Nonetheless, good improvement in impact strength as a result of incorporation of HBP were observed and explained in terms of morphological behavior for a DGEBA matrix modified with various amounts of HBP. (C) 2003 Kluwer Academic Publishers.