The mechanical, thermal and optical properties of a transparent thermoplastic resin which is based on non-crystalline nylon with cross-linking agents were improved by electron beam (EB) irradiation cross-linking. When the EB irradiation power was increased, the yield stress improved by 34% and the glass transformation temperature increased from 116 to 165 degrees C. Transformation from the brittle to the ductile state was observed by the dependence of a strange elastic module on the temperature and EB irradiation power. Above the glass transformation temperature, an optical element produced using this resin could maintain its shape. The birefringence decreased when the EB irradiation power was increased. The decrease of the birefringence was dependent on the initial birefringence value before EB cross-linking. The molecular orientation was relaxed by EB cross-linking. POLYM. ENG. SCI., 2012. (c) 2011 Society of Plastics Engineers