Investigation of Thermally Stimulated Depolarization Current in Epoxy Polymers with Varied Morphology for the Characterization of Interfacial Relaxation Behavior

Adhesive bonds are essential in the field of composite materials, and quality control in composite manufacturing relies on accurate characterization of bonded interfaces. Thermally Stimulated Depolarization Current (TSDC) is a valuable tool for studying relaxation behavior in polymer materials. This behavior can be linked to polarization mechanisms to identify interfacial polarization, a critical feature of bonded joints. Other techniques, such as broadband dielectric spectroscopy, have also been used to characterize dielectric relaxation in polymers. However, interfacial polarization is typically observable only at very low frequencies, which are often challenging or beyond the reach of available instruments. In this study, the TSDC method is employed to identify and characterize interfacial polarization behavior, differentiating between secondary bonding and co-cured bonding in epoxy resin samples. Changes in interface morphology are reflected in relaxation times and corresponding depolarization currents at different temperatures. This method can also be extended to the characterization of the fiber-matrix interface in composite materials.