DURAMID with 45 % of glass fibre (PA 9T) have been successfully modified using beta rays. PA 9T samples were prepared by injection moulding technology and then were irradiated from 33 to 198 kGy in electron accelerator RHODOTRON. The thermal properties (e.g. DSC and TGA) of modified PA 9T samples by beta rays were measured. The tested samples showed significant changes of thermal properties after irradiation. From this point of view, new applications could also be seen in areas where more expensive materials (metals, composites etc.) are used, especially for application in automotive and military industry.