Thermal conductivity enhancement of electrically insulating syndiotactic poly(styrene) matrix for diphasic conductive polymer composites

Abstract

In co‐continuous conductive polymer composites (CPCs) designed for heat generation by the Joule effect, thermal conductivity km of the electrically insulating matrix is the limiting factor to obtain good heat dissipation. To prevent the establishment of non‐desirable high temperature gradient in heating elements, it is necessary to enhance the thermal conductivity of the composite, kc, independently from its electrical conductivity, σ (already optimized). Several adequate fillers for this purpose have been selected, boron nitride (BN), talc (Mg3Si4O10 (OH)2), aluminum nitride (AlN) and aluminum oxide (Al2O3) particles, and their impact on thermal properties and syndiotactic polystyrene phase transition temperatures have been studies. Lewis and Nielson, Cheng and Vachon, Agari and Uno models were used to predict the evolution of thermal conductivity with filler content and were found to describe correctly thermal conductivity of CPCs after the determination of ϕm the maximum packing fraction, A = f(D/l) the shape factor, C1 and C2 parameters function of respectively modifications of crystals and ability of the filler particles to associate into chains. These models show that whatever the filler and unlike electrical conductivity, thermal conductivity does not go through a sharp insulator/conductor (percolation threshold). Only BN shows a real exponential increase of conductivity over 20% v/v filler. Consequently, in best conditions introducing 30% v/v of BN allows the thermal conductivity to be multiplied by six. BN particles were also found to shift the CPCs glass transition temperature (Tg), the non‐isothermal crystallization temperature (Tc,n) and the melting temperature Tm. Copyright © 2006 John Wiley & Sons, Ltd.

Functional composites with core–shell fillers: I. Particle synthesis and thermal conductivity measurements

“…The values of A and u m for many geometric shapes and orientations are available in the literature or can be easy calculated, if parameters of the particles are known [3,39,40]. This model successfully describes the effective thermal conductivity when the thermal conductivity of the matrix is much smaller than that of the filler.…”

“…However, thermal conductivity of neat epoxy resin is the lowest among all the known full-solid materials. Although filled epoxy stands somewhat higher in this respect, with the application of the most common fillers (e.g., talc, glass, quartz, boron nitride, alumina), the thermal conductivity of the material is only a few times higher than for the unfilled epoxy, far from what would be desirable for the effective heat evacuation in many applications [3].…”

Thermal Conductivity of Nanoparticles Filled Polymers

“…Droval and co-workers (Droval et al, 2006) investigated the effect of boron nitride (BN), talc (Mg 3 Si 4 O 10 (OH) 2 ), aluminum nitride (AlN) and aluminum oxide (Al 2 O 3 ) particles, and their impact on thermal properties. Lewis and Nielson, Cheng and Vachon, Agari and Uno models were used to predict the evolution of thermal conductivity with filler content and were found to describe correctly thermal conductivity.…”

Synthesis and characterization of thermoplastic composites filled with γ‐boehmite for fire resistance

“…The impact of filler onto the polymer crystal phase can be assessed by measuring the transition temperatures. The crystallization temperature depends on the nuclei speed which can be improved by a nucleation effect of the filler, and the melting temperature is generally related to the crystallite thickness [25].…”