Study of the Complex Permittivity of a Polyurethane Matrix Modified by Nanoparticles

This study presents the influence of various types of nanoparticle (NP) fillers incorporated into a polyurethane (PU) (VUKOL 022) matrix and its subsequent changes in complex permittivity. Two types of surface modification of SiO
₂
fillers were investigated. The frequency dependence of the real and imaginary parts of complex permittivity was measured within the frequency range of 1 mHz to 1 MHz using the capacitance method. The 1 wt.% NPs in PU caused an increase (MgO, TiO
₂
, n-SiO
₂
, and f-SiO
₂
) or a decrease (d-SiO
₂
) in the real permittivity. The α-relaxation and intermediate dipolar effect were observed at the temperature dependence of the imaginary permittivity. The change in permittivity by various surface modifications of SiO
₂
and other nanofillers was discussed based on the multi-core model. Moreover, the NPs caused a shift in the local maximum of the permittivity, which was a result of the interfacial polarisation and a charge multiplication of the α-relaxation process.