Modeling the dielectric response of epoxy based nanocomposites

The dielectric response of epoxy based nanocomposites is simulated by developing 3D models in Matlab. Two different sets of nanocomposites are simulated. In the first one, aluminum oxide is used as a filler with an average particle size of 25 nm. The second set consists of epoxy filled with hexagonal boron nitride nanoparticles with an average size of 70 nm. Both sets of nanocomposites exhibit the same trend. At a relatively low filler concentration, the relative permittivity of the nanocomposites is lower compared to both the matrix and filler. However, as filler content increases, the relative permittivity increases as well. At 5 and 10 vol.% filler concentration, epoxy - boron nitride nanocomposites exhibit a relative permittivity which is higher than that of the filler and matrix. Re-organization of the polymer matrix due to the presence of fillers and water uptake are taken into account in the developed models. The model results fit well with the experimental data when two layers are considered around the particles. The first layer is a thin layer with a small thickness and high relative permittivity while the second one extends several nanometers in the polymer matrix. The thickness of the outer layer is dynamic and depends on the filler concentration. The relative permittivity of the outer layer is assumed to be lower than that of the base material.