Thermal Conductivity of Carbon-filled Polypropylene-based Resins

Varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon nanotubes) were added to polypropylene, and the resulting single-filler composites were tested for thermal conductivity using the nanoflash test method. In addition, the effects of single fillers and combinations of different carbon fillers were studied via a factorial design. Each single filler caused a statistically significant increase in through-plane thermal conductivity at the 95% confidence level, with synthetic graphite causing the largest increase, followed by carbon nanotubes, and then carbon black. The synthetic graphite/carbon nanotube formulations, followed by the carbon black/synthetic graphite formulations also caused a statistically significant increase in composite through-plane thermal conductivity. Composites containing 75 and 80 wt% synthetic graphite in polypropylene had an in-plane thermal conductivity of 24 and 34 W/m·K, respectively. This meets the thermal conductivity target of >20 W/m·K for fuel cell bipolar plates.