Heating Effects on Structural and Electrical Properties of Polyetherimide

Problem statement: Polyetherimide (PEI) has several uses such as electrical insulation. It can undergo different constraints like heat or high voltage which influence its performances as insulator. In this study, the effects of heating on structural and electrical properties of polyetherimide (Ultem 1000) are studied. Approach: PEI samples were heated at different temperatures below the glass transition temperature (175, 190 and 205°C). Different complementary techniques were used to investigate structural alterations and dielectric relaxations. These are infrared (IR) spectroscopy, Differential Scanning Calorimetry (DSC), Thermally Stimulated Depolarisation Current (TSDC) technique and Dielectric Spectroscopy (DS). Results: Physical ageing was revealed in heated samples by DSC analysis. DS and TSDC results have shown that dipolar relaxations are affected by heating. The amount of relaxing dipoles decreases when the material is heated at 190°C. Conclusion/Recommendations: The heating of polyetherimide at 190°C leads to a stabilisation of charges in deeper energetic levels which influences the insulating character of the material.