Thermoplastic materials can be used as electrical insulation in various indoor applications when the proper electrical design and suitable manufacturing method are combined. The aging property of these thermoplastic materials is of great interest, in addition to their basic mechanical, thermal and electrical properties. A non-standard method has been developed within this work, where flat thermoplastic material specimens could be stressed by temperature, electrical field and pollution. Standard inclined-plane tracking and erosion test electrodes were used. A leakage current monitoring system has also been developed to detect the failure. Various thermoplastic materials were tested and differences in performance were noted. The relationship of this test method to the relevant IEC standards was also discussed.