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

Abstract

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.

Influence of Nanoparticles on the Dielectric Response of a Single Component Resin Based on Polyesterimide

“…The direct dispersion method was used for this purpose. As was demonstrated in previous studies [ 26 , 32 , 33 ], this mechanical method, coupled with other technological procedures, can lead to proper dispersion of nanoparticles in polymer matrices. A controlled dispersion procedure using ultrasound was used next as an efficient, clean and rapid technological procedure.…”

“…The nanofillers used in this experiment were also selected on the base of previous works [ 11 , 13 , 26 , 32 , 47 , 48 ], where they provide improvement of the insulating and dielectric properties of the studied NCs. Due to their experimental results, the NCs with these nanoparticles are adapted to the strict insulation requirements of high-voltage power equipment to meet the demands of growing power generation and consumption.…”

“…The frequency-temperature dependencies of the real and imaginary parts of the complex relative permittivity were measured within the frequency range of 1 mHz to 1 MHz with increasing temperature from +20 °C to +120 °C. IDAX 350 dielectric analyzer (Group Limited, Dallas, TX, USA) and a QuadTech 7600+ precision LCR meter (IET Labs, Inc., Boston, MA, USA) with a self-designed three-electrode system were used for this purpose, like in previous works [ 26 , 32 ].…”

“…A number of different processes (such as the -, - and -relaxations and the Maxwell-Wagner-Sillars (MWS) effect) in an AC electric field, the intermediate dipolar effect (IDE), and DC conductivity were described in [ 26 ] relation to polarisation mechanisms. It is generally observed that molecule-to-molecule motion among chains is activated during the glass-transition process, and that the -relaxation observed on NCs is connected with the glass transition process.…”

A Comprehensive Study of Polyurethane Potting Compounds Doped with Magnesium Oxide Nanoparticles

“…The size and uniformity of the agglomerates vary with the filler content within the polymer matrix, which applies to both studied materials and the final shape is most likely due to the predominance of MgO particles with ellipsoidal morphology. From previous experience [ 26 , 48 ], an inferior level of filler dispersion is expected from the beginning of the experiment, as a simple oxide filler is purposefully used without any surface treatment. It is of course possible to apply a surface treatment for better particle dispersion [ 49 , 50 , 51 ], but the relatively high viscosity (related to the polymer molecular weight) of the base material is more important in this case [ 52 , 53 ].…”