Electron-beam irradiation of injection-molded specimens of polyiminohexamethyleneiminoadipoyl (better known as polyamide-6,6) was carried out in air at ambient temperature (303 K) and a high temperature (393 K). Most of the irradiated specimens were tensile dumbbells, although a few were cylinders for compressive stress relaxation testing. A few representative samples were dipped in triallyl cyanurate (TAC) solution before ambient-temperature irradiation. The gel content of the specimens increased with radiation dose and the temperature of irradiation. Moreover, the TAC-treated specimens showed an increase in gel content over the neat specimens irradiated at the same dose levels. Wide-angle X-ray scattering and differential scanning calorimetry studies revealed that the crystallinity decreased with increasing radiation dose. Irradiation at the high temperature and treatment with TAC further decreased the crystallinity compared to irradiation at ambient temperature. As determined from compressive stress relaxation and mechanical and dynamic mechanical properties, the optimized radiation dose for ambient-temperature radiation was 200 kGy. The gels had a stiffening effect, and the rate of relaxation decreased significantly. The water-uptake characteristics of the tensile specimens were investigated; this revealed a decrease in the water absorption tendency with increasing gel content. (c) 2005 Wiley Periodicals, Inc.