Control of Dielectric Parameters of Micro- and Nanomodified Epoxy Resin Using Electrophoresis

This work presents the results of research on submicro- and nanocomposites with gradient properties, produced in a planned electrophoretic process. Epoxy-resin-based samples were filled with TiO2 particles of three different sizes (13 nm, 38 nm, and <1 µm) at four different values of average electric field Eav (0.0 Vmm−1, 125 Vmm−1, 250 Vmm−1, and 500 Vmm−1) for 1 h each. Changes in selected dielectric parameters (dielectric constant εr and dielectric loss factor tanδ) of the composites were analyzed using broadband dielectric spectroscopy (10−1 Hz to 105 Hz). The influence of the Eav and the current i(t) flowing through the sample material and the Joule heat generated in it on the resin curing process and the final gradient of dielectric parameters were investigated. The results show that the degree of modification of the εr gradient increases with increasing Eav and is more pronounced in the case of TiO2 nanoparticles. The largest modifications in the εr and tanδ were obtained for nanoparticles with a diameter of 13 nm at Eav = 500 Vmm−1, while the lowest for particles < 1 µm at Eav = 125 Vmm−1. The effect of electrophoresis on the dielectric parameters is significant, especially near the anode region. Increasing the concentration of TiO2 particles at the anode occurs at the expense of reducing their concentration in the remaining volume of the sample. The test results clearly demonstrate the importance of particle dimension and electric field strength for the gradient modification of the properties of the epoxy composite using electrophoresis. Numerical simulations of electric field stresses in the epoxy resin during the electrophoresis process, performed in the COMSOL program, revealed a significant increase in the E field strength in the areas close to the anode and cathode.