Investigation on thermal stability and flame spread behavior of new and aged fine electrical wires

Thermal properties and fire propagation performance were studied for the new and aged electrical wires. Two fine electrical wires were tested using the DSC-TG and a flame spread apparatus. The main objective is to understand the thermal aging effect because the aging of electrical wire is inevitable in real service conditions. The significant discoloration occurs for PC sample during the thermal aging, while slightly changes for PN sample. The microstructure of all samples surface presents relatively smooth. The diffusion of metal from inner core to polymer insulation was discovered by the XPS. The change of these parameters including melting temperature, heat of melting, onset temperature of decomposition, mass loss, etc., is observable and complicated. The metal core also has the effect on properties of polymer insulation during the thermal aging. The difference of thermal properties between new and aged electrical wires shows that the chemical composition and structure of polymer insulation change due to thermal degradation and metal catalysis. Finally, the influence of thermal aging on the flame spread rate was also discussed. This study indicates that thermal aging coupled with the metal catalysis can promote the degradation and change the thermal or fire spread properties of polymer materials.