Dielectric constant and breakdown strength of polymer composites with high aspect ratio fillers studied by finite element models

BisGMA-polyvinylpyrrolidone blend based nanocomposites reinforced with chitosan grafted f-multiwalled carbon nanotubes

“…The values of dielectric constant of nanocomposites was enhanced at a frequency of 1 MHz with the incorporation of a nanofiller into the neat blend system which further displayed improvement due to the CS grafted MWCNTs. The values of dielectric constant of nanocomposites increased with increasing content of CS/f-MWCNTs due to its high aspect ratio [22].The surface modification of f-MWCNTs with CS also causes effective nanofiller-matrix interactions i.e. BGP 50 and CS/f-MWCNTs giving rise to a homogeneous phase system with increased dielectric constant.…”

“…The nanocomposites are able to exhibit increased conductivity due to the conductive effect of CS/f-MWCNTs. It was observed that at higher loading (7 wt%), the filler particles tend to come closer to each other, thereby increasing the aggregation at matrix-filler interface which creates a barrier for the conduction of electric current [22]. Fig.…”

Filler orientation effect on relative permittivity of dielectric elastomer nanocomposites filled with carbon nanotubes

“…Although MG rule of mixture predicts the increase of the effective dielectric constant with the dielectric constant of the fillers, it does not consider the effects of the high aspect ratio and its distribution, and the rod-like shape of MWNTs. For nanocomposites with fillers of high aspect ratio and rod-like shape, the effective dielectric constant of the nanocomposites is not sensitive to the dielectric constant of MWNTs when the contrast between the dielectric constant of MWNTs and that of dielectric elastomer is large enough [10]. For instance, when the filler dielectric constant varies from 5000 to 120,000, the effective dielectric constant of the nanocomposites increases for 3.4%, from 3.81 to 3.94, in a model with filler aspect ratio 20 and filler weight fraction of 0.75%.…”

“…As a result, fillers parallel to the applied electric field can significantly enhance the effective dielectric constant, while the ones perpendicular to the applied electric field do not have primary impact on the effective dielectric constant. Many theories have been developed to predict the effective dielectric constant of composite materials such as Maxwell-Garnett (MG) rule of mixture [23,24], and finite-element-based approaches [10,25]. Some works have also focused on the filler orientation effects on both electrical and mechanical properties in extreme cases [18,[26][27][28].…”

“…A high electric field of at least 10-30 V/lm is required for the actuation of DEs, which limits the practical applications especially in biomedical fields [2,7]. A common solution to the disadvantages of DEs is to enhance their relative permittivity by implementing ceramic powders with high dielectric constant such as TiO 2 particles [8], BaTiO 3 nanoparticles [9][10][11] and PbTiO 3 [12,13] to generate high electromechanical responses with lower applied field level. However, high loading, up to 20-30 vol.% of these particles are required for meaningful increase, at which the ceramic powders filled composite materials could lose its flexibility, leading to limited improvement of the electromechanical response.…”