Dielectric and mechanical properties correlated to physico-chemical characteristics of a polyester-imide resin used in rotating machines insulations

This work is focused on the characterization of dielectric, mechanical and physicochemical properties of a commercially available PEI resin. The complex shear modulus is determined using the Dynamic Mechanical Analysis (DMA). The complex dielectric permittivity is measured using the broadband dielectric spectroscopy. In order to complement the mechanical and dielectric results, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) experiments are performed. The dynamic mechanical results show an important and continuous decrease in the storage modulus. The dielectric results present a significant increase in the dielectric losses, especially for the low frequencies. Both of these results show an important diminution in the material viscosity. The increase in dielectric values suggests an increase in the ionic conduction. On the other hand, the decrease in elastic modulus implies a rubber-like behavior of the material. The mechanical and dielectric results are in a good agreement with the DSC and TGA results.