Synergistic effects of multiple carbon fillers on the rheology of liquid crystal polymer based resins
Adding conductive carbon fillers to insulating thermoplastic resin increases composite electrical and thermal conductivity. Often, as much of a single type of carbon filler is added to achieve the desired conductivity, while still allowing the material to be molded into a bipolar plate for a fuel cell. In this study, varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX liquid crystal polymer. The rheology of resulting single filler composites was tested. In addition, the rheological properties of composites containing combinations of two different carbon fillers were studied via a factorial design. In all cases, viscosity increased with increasing filler volume fraction for all shear rates. Over the range of shear rates studied, the viscosity followed a shear-thinning power law model. The factorial design results indicated that each of the single fillers and all of the two filler combinations caused a statistically significant increase in composite viscosity at a shear rate of 1,000 s -1. The composites containing carbon black and synthetic graphite caused the largest increase in viscosity. It is possible that the highly branched, high surface area structure of carbon black 'links' with the synthetic graphite particles, which results in increased composite viscosity. © 2008 Society of Plastics Engineers.
Synergistic effects of multiple carbon fillers on the rheology of liquid crystal polymer based resins.
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