Low-Frequency Dielectric Response of Epoxy-Based Polymer Composites

The low-frequency dielectric response of polymeric materials, typically in the range of 10^-5 to 10² Hz at room temperature, is related to various phenomena. Direct conduction, quasi DC conduction also known as low-frequency dispersion, alpha dipolar relaxation mechanisms, which are located in the low-frequency part of the spectrum for glassy polymers, are included in these phenomena and appeared generally below 1 Hz. The presence of a load, nano or micrometric in size, is known to significantly affect the low-frequency dielectric properties of the based matrix. New mechanisms related to the morphology and interfacial effects, such as the Maxwell-Wagner interfacial polarization, could then superimpose to the already existing relaxation mechanisms. In order to further investigate the low-frequency response of various reinforced epoxy-based composites, both time and frequency domain spectroscopy were conducted. Different types of epoxy microcomposites containing a high content of quartz, i.e. 60% wt. and microcomposites load with SiC particles, were prepared. Measurements were also performed on epoxy-mica composite made of paper-backed mica flakes bonded by the resin.