On the ‘curiosity’ of electrical self‐heating, static charge and electromagnetic shielding effectiveness from carbon black/aluminium flakes reinforced epoxy‐resin composites

Abstract

This paper shows the wide application range (such as electrical self‐heating and electromagnetic shielding effectiveness) of composites consisting of conductive carbon black/aluminum flakes (CBA) filler and epoxy insulative matrix. The effect of CBA content on the network structure of epoxy matrix was investigated in detail. Static electrical conductivity increases linearly with the increase of filler concentration at the interface in epoxy composites. The large decrease of the conductivity as a function of the temperature is analyzed in terms of the negative temperature coefficient of conductivity (NTCC) effect. The influence of viscosity, surface energy and barrier highest energy on the NTCC behaviour in the composite is also considered. Based on these results, a new interpretation is proposed to explain the NTCC phenomena by computing the swelling force among conductive phases. The correlations of conductivity during the temperature cycling and activation energy were analyzed. The effects of dynamic ageing at various temperatures on the resistivity are reported. Current–voltage–temperature characteristics for epoxy with different contents of CBA were examined in detail. A model based on the law of energy conservation is proposed to calculate the specific heat and amount of heat dissipation. The static charge of the epoxy–CBA composites was estimated. The correlation between electromagnetic wave‐shielding effectiveness (EMS), conductivity and frequency of epoxy composites with different filler contents is also discussed. Furthermore, the effect of annealing on EMS of epoxy composites was examined. © 2002 Society of Chemical Industry

New antistatic charge and electromagnetic shielding effectiveness from conductive epoxy resin/plasticized carbon black composites

“…Furthermore, increasing the CB content makes CB particles more crowded and linked, leading to the rapid increase of bulk conductivity. This indicates that the conducting particles come into contact with each other or closed up enough to allow the carriers mobility hop by tunneling, thus forming continuous conducting mesh [4]. A feature of interest in this figure is the critical concentration i.e.…”

“…7a and 7b, respectively. It is clear that the real and imaginary permittivity increase with increasing CB content in composites, due to the fact that the CB particles get closer to each other, resulting in an increase of permanent electric dipoles within the composites [4,15]. Also the real and imaginary permittivity decrease with increase in frequency.…”

“…Electrically conductive polymer composite is obtained when conductive particles such as metal powder, carbon black (CB), and carbon fiber etc. are implanted to an insulating polymer matrix [4][5][6][7][8]. The level of electrical conductivity in these heterogeneous materials depends primarily on the concentration and geometry of the filler [9][10][11].…”

Novel V‐shaped negative temperature coefficient of conductivity thermistors and electromagnetic interference shielding effectiveness from butyl rubber–loaded boron carbide ceramic composites

“…The PTCC effect is attributed mainly to two reasons: (1) at T c the separation distance between B 4 C particles becomes so large, simultaneously, the intrinsic conduction attributed to the carriers of the host materials begins to appear; and (2) the diffusion of charge carriers decreases at high temperature because of the increase of viscosity and decrease of the surface energy of the rubber matrix. 1,4 The increase of viscosity and the decrease of surface energy lead to an increase of the compact swelling attributed to the formation of rich liquid phase, thus creating a new stress-swelling stress-in the polymer matrix. This swelling stress increases the anisotropic and surface energy of conductive filler changes, so the conductive networks will be pushed apart from each other, forming a thin screen and/or membrane barrier within the rubber matrix and therefore PTCC appears.…”

Evaluation of gamma rays shielding competence for bentonite clay /PVA polymer matrix using MCNPX code

“…Polymeric composites containing inorganic additives became the most popular shield against gamma rays and many studies investigated their shielding properties [6][7][8]. Polymeric nanocomposites have a great potential for improving shielding properties [9][10][11]. The simulation method for investigation of radiation interaction is found radiologically safer, less time consuming, cost effective and applicable for desired energy of radiation.…”