Role of interface in highly filled epoxy/BaTiO₃ nanocomposites. Part II-effect of nanoparticle surface chemistry on processing, thermal expansion, energy storage and breakdown strength of the nanocomposites

Highly filled dielectric polymer nanocomposites with high dielectric constant nanoparticles (e.g., BaTiO₃) have promising application in many fields such as energy storage. The effectiveness of these nanoparticles to increase the dielectric constant and energy density of the resulting nanocomposites has already been demonstrated. However, the role of interface between the nanoparticles and polymer matrix on thermal expansion, energy storage and breakdown strength-the three parameters that are important for practical application of the dielectric polymer nanocomposites, has not been systematically documented. In this contribution, we investigated the effect of six kinds of nanoparticle surface chemistry on the processing, coefficient of thermal expansion, energy storage and breakdown strength of highly filled epoxy/BaTiO₃ nanocomposites. It was found that all these aspects, in particular the processability of the nanocomposites, are associated with the nanoparticle surface chemistry. Combining the processability, coefficient of thermal expansion, energy storage and breakdown strength of the nanocomposites, we conclude that the nanoparticles functionalized by silane coupling agents with terminal groups capable of reacting with the epoxy matrix are more suitable for preparing highly filled dielectric polymer nanocomposites.