Thermal properties of carbon nanofiber reinforced high-density polyethylene nanocomposites

Reinforcing polymers with the appropriate nanofillers is an effective way to obtain a variety of enhanced material properties. In this paper, high-density polyethylene nanocomposites reinforced with either pristine or silane-treated carbon nanofibers at various weight percentages (0.5wt%, 1wt%, and 3wt%) were fabricated through melt-mixing and compressive processing. Silane coatings with two thicknesses, 2.8nm and 46nm, were applied on the oxidized carbon nanofibers to improve the interfacial bonding between the carbon nanofibers and the matrix. Scanning electron microscopy and transmission electron microscopy demonstrated the dispersion of carbon nanofibers and the strongly improved interfacial adhesion between the carbon nanofibers and high-density polyethylene matrix due to the silane coating. The thermal properties of high-density polyethylene / carbon nanofiber nanocomposites were characterized and compared with those of the neat high-density polyethylene. The measurement results showed that the thermal conductivity of the high-density polyethylene /carbon nanofiber nanocomposites increased with the carbon nanofiber loading. The enhancement of thermal conductivity was not only due to the high thermal conductivity of carbon nanofibers but also due to the interfacial quality between the carbon nanofibers and the high-density polyethylene matrix. The interfacial thermal contact resistance between the carbon nanofibers and the matrix was determined to be in the range of 0.88x10-6m2K/W to 3.89x10-6m2K/W. Furthermore, the coefficient of thermal expansion of the nanocomposite was found to be reduced by the incorporation of carbon nanofibers.