Synergistic effects of multiple carbon fillers on the rheology of liquid crystal polymer based resins

Abstract

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 21 . 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.

Comparison of rheological properties of carbon nanotube/polycarbonate and carbon black/polycarbonate composites

“…In Figures 14 and 15, as CB is added to the PC, the steady shear viscosities of the resulting composites are observed to increase from 700 to 2000 Pa s. This is the expected behavior, as most carbon/thermoplastic composites show an increase in viscosity as filler loading is increased 27, 42–46. At all shear rates, the viscosities rise as CB is added to the polycarbonate.…”

“…11). This is unusual behavior, as most carbon/thermoplastic composites show an increase in viscosity as filler loading is increased 27, 42–46. At still higher loadings (4–8 wt % CNT in Fig.…”

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

“…9). Figure 9 includes data reported here and previously reported,39 which include combinations of fillers with 4 wt % CB (4CB), 40 wt % SG (40SG), and 10 wt % CF (10CF). Two‐filler blends of SG and CF with Vectra follow the same curve of the relative viscosity versus the volume fraction of carbon as was traced by the single‐component composites of these materials.…”

A Review of Thermoplastic Composites for Bipolar Plate Materials in PEM Fuel Cells

“…The bipolar plates had density of 1.6 gcm -3 , specific bulk conductivities 150 Scm -1 and material prices between 2 and 10 Euro kg -1 . Even though, the investigations showed that the electrical conductivity and ability of injection moulding process can be improved significantly, three carbon fillers always resulted in an increased viscosity [44] . Fig.…”