Preparation of epoxy-methacrylate prepolymer and electron beam curing of its mixture with monomers

Epoxy methacrylate prepolymer was synthesized from methacrylic acid and a diglycidyl ether type low molecular weight epoxy resin, and the electron beam curing of the prepolymer was studied using styrene and polyethyleneglycol dimethacrylates as comonomers. The esterification was carried out quantitatively without any side reaction by adding more than 250 ppm hydroquinone and less than 1 %(wt) triethanolamine by wt. of methacrylic acid, respectively. In the radiation curing under air atmosphere, the maximum gel fraction was observed at 10-13% monomer contents. The rate of gel formation was decreased by the presence of unreacted epoxy group and acid in the prepolymer and increased with increasing degree of polymerization of polyethyleneglycol block in the dimethacrylates. Considerable oxygen effect in the curing, particularly when polyethyleneglycol dimethacrylate was used as a comonomer, was recognized through the differences of the product properties, though no remarkable differences were found in the rate of gel formation in air and nitrogen atmosphere. (author)