Polymer composites containing plasma‐treated mica. II. Dielectric properties

Abstract

SynopsisThe complex relative permittivity K* ( w ) of polymer-mica composites has been studied in the frequency range extending from about to lo7 Hz. Microwave plasma treatment in ethylene of the mica flakes leads to significant alterations of K * ( w ) for three matrix polymers used-polyethylene, polystyrene, and a mixture of these two polymers. The origins of the dispersion characteristics were investigated using a series of polyethylene samples containing up to 50 wt-% of untreated mica. Comparing experimental results with theoretical analyses of the.Maxwel1-Wagner interfacial polarization effect, it is possible to identify two major contributions to K*(w): a Debye-like dispersion centered near lo2 Hz and a charge-diffusion mechanism which contributes primarily at low frequencies (510 Hz).

Dielectric permittivity and breakdown characteristics of polymer-mica composites

“…Very briefly, we may conclude the following: 1. Referring to Figure 2b, the losses are composed of two terms: the expected "Debye" peak, and a lal'l frequency term K" ~ Cf-x (x -+ 0.5) (5) This latter contribution, due to diffusion of space charges, has been predicted theoretically by Goffaux 10 . 2.…”

Dielectric relaxation and electro-optical switching behavior of nematic liquid crystal dispersed in poly(methyl methacrylate)

“…The phenomenon called interfacial polarization is observed in a heterogeneous dielectric system; which is governed by MaxwellWagner effect. This polarization is perceived as being the migration of charge carriers to the boundaries between components of the heterogeneous system under the influence of applied electric field [15]. In such a system LC organization within the droplets is governed primarily by polymer-LC interfacial interactions and LC-LC interactions [28].…”

“…The study of dielectric property can be used to detect these electric complexities over a wide temperature and frequency range, and is also very sensitive to the DC conductivities due to conducting impurities and the interfacial charge layer effect. The existing theories on dielectric behavior in these kinds of heterogeneous systems can be adapted to the PDLC systems as a result of its phase separated nature [15]. The Maxwell-Wagner (MW) effect due to charge accumulation between boundaries of LC droplets and surrounding of polymer matrix has been observed by J. Liu et al [16].…”

Investigation of liquid crystal dispersion and dielectric relaxation behavior in polymer dispersed liquid crystal composite films

“…The interfacial charge layer effect giving rise to polarization is also known as the Maxwell-Wagner effect [12]. This polarization is generally attributed to the migration of charge carriers to the boundaries between components of the heterogeneous system under the influence of an applied electric field [13]. B.R.…”