A novel way of enhancing the electrical and thermal stability of conductive epoxy resin–carbon black composites via the Joule heating effect for heating‐element applications

Abstract

ABSTRACT:The influence of Joule heating treatments and carbon black (CB) on the electrical and thermal behavior of epoxy resin composites is well described in this article. The effect of CB and Joule heating on network structure characteristics, such as shrinkability, interparticle distance between conductive particles, crosslinking density, hardness, thermoelectric power, thermal conductivity, the thermal expansion coefficient, and scanning electron microscopy, of epoxy composites was investigated. The electrical conductivity () of epoxy resin correlated with the volume fraction of CB and Joule heating treatment. increased continuously with increasing CB content, and Joule heating increased the level of , which makes it attractive for electronic utilization. The for fresh and Joule heating samples was recorded during heating-cooling cycles. The conduction mechanism of for epoxy composites was identified. The activation energy and hopping energy for two batches of epoxy as a function of CB content were estimated. The hopping distance, the state density at the Fermi level, and the radius of localized wave function versus CB content were evaluated. The current-voltage-temperature characteristics of fresh and Joule heating samples of epoxy composites were demonstrated. The thermal reliability was tested by means of temperature-time characteristics when certain applied power was on and off for several cycles. The specific heat and amount of heat transfer by radiation and convection were calculated based on the energy balance model for two batches. The results indicate that the Joule heating effect is a very effective and prospective way of enhancing the electrical and thermal stability of epoxy-CB composites for consumer use as heaters and in other electronic areas such as electromagnetic shielding effectiveness.

An experimental study of dynamic behaviour of graphite–polycarbonatediol polyurethane composites for protective coatings

“…Since polymers are, in general, insulating materials, many efforts have been directed to improve their electrical conductivity [1,2,3]. Electrically insulating polymers such as polyurethane can be specifically modified in order to increase its conductivity by dispersing conductive fillers [4,5].…”

Room temperature resistance relaxation behavior for carbon black filled conductive polymer composites

“…22 Particularly, since the gap distance between filler aggregates critically depends on u, it is expected that the amplitude of Joule heat induced resistance relaxation also exhibits marked concentration dependence. As shown in Figure 2(a), PMVS/CB composite containing 9.1 vol % CB shows more obvious resistance decrease than that containing 13.1 vol % CB because the closer to the percolation threshold the farther away from perfect is the percolation network and therefore more fragile.…”

“…The PTC effect strongly depends on the time related thermal history, 19,20 so that thermal aging is becoming a common method to eliminate the thermal history and to stabilize the conduction behavior. 21,22 Tao et al 23 and Park et al 24 found that annealing at temperatures below and above T m has different influences on the redistribution of filler aggregates in the matrix and also on the PTC/NTC behavior of CPCs. Their observations were confirmed by Song and Zheng,20 and were explained with respect to the breakdown and reformation of the percolation network at lower temperatures, as well as the agglomeration of carbon black (CB) aggregates and formation of percolation network in the melts.…”

Plasticized/graphite reinforced phenolic resin composites and their application potential

“…1,2 The increasing requests for thermistors, temperature controllers, self-heaters, gas sensors, electrostatic charge dissipation, and electromagnetic interference (EMI) shielding are pushing many researchers to explore new concepts and related materials. [3][4][5][6][7][8][9][10] Electrically conductive polymer composites (CPCs) are obtained by the blending of an insulating polymer matrix with conductive fillers such as carbon black, carbon fibers, and graphite or metal particles.…”