Miscibilization of Low Molecular Weight Functionalized Polyethylenes in Epoxy Resins. Part 2. Effects of Curing on Morphological Features and Mechanical Properties

An investigation was carried out to study the toughening of diglycidyl ether of bisphenol A epoxy resins (DGEBA) with several chemically modified low molecular weight polyethylenes, possessing hydroxyl functionality. The miscibility of the functionalized polyethylenes in DGEBA resin was found to be strictly dependent on the number of functional groups contained in the chains. Solubilization in the epoxy resin was achieved by reacting the functionalized polyethylenes with a monofunctional epoxy resin homologue, in order to produce telechelic branches attached to the chains. The addition of such chemically modified polyethylenes to an anhydride/hardener/epoxy resin mixture has given rise to the formation of a two-phase microstructure in the cured systems, consisting of small spherical aggregated particles strongly bonded to the surrounding matrix, thereby providing the required mechanism for toughness enhancement. The morphology and mechanical properties of such systems are compared to those obtained with a traditional toughening agent for DGEBA epoxy resins