Polymer-filler interactions and polymer chain dynamics in the interphase in silicon nanocomposites

Enhanced electrical properties of nanocomposites are attributed to the so called interphase which can be formed between the polymer matrix and the filler particles. It was shown that Electric Force Microscopy (EFM) is an appropriate method to give an evidence for the existence of the interphase in polymeric nanocomposites and to determine its extension. The aim of the present work is to give an insight in polymer-filler interactions and polymer chain dynamics in the interphase in silicones filled with nanoscale silica filler particles. Two materials based on the same silicon matrix material with different filling degrees of two different types of spherical silica nanofillers (F1 and F2) were prepared. For the different materials the resistance to high voltage arcing was investigated and EFM was applied to determine the thickness of the interphase in both systems. Investigations on polymer-filler interactions and polymer chain dynamics in the interphase were performed with Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR). FTIR measurements show that there is no chemical bonding between the filler particles and the polymer matrix. From NMR investigations it can be concluded that the addition of fillers has an influence on the dynamic of the polymer chains in both materials. However, from a comparison of the resistance to high voltage arcing of the different investigated materials and the results of the NMR investigation it seems that polymer chain dynamics seem not to be the main factor of influence on the resistance to high voltage arcing of the used materials.