Maleic acid was esterified with ethylene or/and 1,2-propylene glycols under addn. of cyclopentadiene and the resulted polyester was dissolved in styrene, diethylene glycol dimethacrylate or their mixt. and crosslinked with Co octanate and N,N-dimethyl-p-toluidine under control of the styrene emission. The emission was decreased when styrene was partly replaced with the dimethacrylate. Addn. of the dimethacrylate resulted, however, in deterioration of mech. properties of the crosslinked polymer.