Effects of filler on electrical and rheological properties of polypropylene thermally conductive composites

Polypropylene thermal conductive composites with different hybrid fillers were prepared, and the thermal conductivity, electrical conductivity and rheological properties were tested. The results show that the thermal conductivity is improved by adding hybrid parts. By adding 10% of carbon black and carbon nanotube simple mixture and chemical bonded filler to PP/Al2O3 composite, the thermal conductivity is improved to 0.60 W/mk and 0.63 W/mk, respectively. Using pure carbon black and pure carbon nanotubes as hybrid parts, the thermal conductivity is only 0.36 W/mk and 0.45 W/mk. The volume resistance declines 106 order of magnitude for the composite using carbon nanotube and the simple mixture, whereas the composite filled with pure carbon black or chemical bonded fillers show insulation behavior. An obvious shear thinning phenomenon appears in η* vs. ω curves after adding hybrid parts. A second plateau at low frequency region is observed, but it is very weak for the chemical bonded filler modified composites. For this composite, the microstructure shows that the filler distributes well in the matrix and connecting bridges are formed between the fillers. The results show that the thermal conductivity cannot be improved pronouncedly by pure carbon black or pure carbon nanotube. The simple mixture of carbon black and carbon nanotube can induce better thermal conductivity, but it will also lead to some electrical conductivity. The application of chemical bonded carbon black and carbon nanotube can meet the demand of thermally conductive and insulated composites. ©, 2015, Chengdu University of Science and Technology. All right reserved.