Synergistic Effects of Carbon Fillers in Thermally Conductive Liquid Crystal Polymer Based Resins

Abstract

Thermally conductive resins are needed for fuel cell bipolar plates. Varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX Liquid Crystal Polymer. The resulting single filler composites were tested for thermal conductivity. In addition, the effects of single fillers and combinations of two different carbon fillers were studied via a factorial design. Synthetic graphite caused the largest statistically significant increase in composite through plane and in plane thermal conductivity. Composites containing synthetic graphite/carbon black and synthetic graphite/carbon fiber caused a statistically significant increase in through plane and in plane thermal conductivity.

Effects of carbon fillers on the thermal conductivity of highly filled liquid‐crystal polymer based resins

“…Carbon black did increase the composite thermal conductivity, which is shown in Figure 4 21,24 created pathways that increased the composite thermal conductivity even at low filler concentrations. Again, because of the large increase in composite melt viscosity, carbon black was only used at low loading levels.…”

“…22,23 The properties of this polymer are summarized in Table I, and additional information has been reported elsewhere. 21,22 The first filler used in this study was Ketjenblack EC-600 JD. This is an electrically conductive carbon black available from Akzo Nobel, Inc. (Chicago, IL) The highly branched, high-surface-area carbon black structure allows it to contact a large amount of polymer, which results in improved electrical and thermal conductivities at low carbon black concentrations (often 5-7 wt %).…”

“…24 A diagram of the carbon black structure has been given elsewhere. 21,24 The second filler used in this study was Asbury Carbons' Thermocarb TC-300 (Asbury, NJ). This is a synthetic graphite that was previously sold by Conoco, and its properties are shown in Table I.…”

“…A photomicrograph of these synthetic graphite particles has been shown elsewhere. 21,25 Fortafil 243 carbon fiber, sold by Toho Tenax America, Inc., was the third filler used in this study. Fortafil 243 is a polyacrylonitrile-based, 3.2-mm chopped and pelletized carbon fiber that is often used to improve the electrical and thermal conductivities and tensile strengths of resins.…”

“…However, the carbon black/carbon fiber combination was not statistically significant. 21 Hence, the filler levels chosen did change the filler effect terms.…”