Epoxy networks modified by unsaturated oligoesters and acrylates or methacrylates

We have studied the formation of networks on the basis of an epoxy resin called ED-20, the same resin modified with tert -butylhydroperoxide (called ED-20P), unsaturated oligoesters and polyethylenepolyamine in the presence of acrylates and methacrylates at 20 degrees C, 100 degrees C and 130 degrees C. The gel-fraction contents in the blends and the pendulum damping hardness of films made from the blends have been determined. The progress of gelation has been related to the composition, time and crosslinking temperature. The presence of peroxide groups enhances the extent of gelation. When those groups are present, acrylates and methacrylates provide still higher values of the ultimate gel fractions, acting as diluents ( lowering viscosity of the initial blends) and simultaneously as crosslinking agents. The pedulum damping hardness tests for organic films performed as a function of time provide results parallel to those obtained by the gel fraction determination via Soxhlett extraction with acetone. Thus, both methods can be used to pursue the progress of gelation.