Effect of filler size on thermophysical and electrical behavior of nanocomposites based on expanded graphite nanoparticles filled in low-density polyethylene matrix

Abstract

Various aspects of electrical and thermophysical properties of nanocomposites based on low-density polyethylene matrix filled with nanostructuralized expanded graphite (EG) and standard, microsized graphite are presented in this article. A periodical method developed in the laboratory was used to measure simultaneously thermal conductivity, specific heat, and diffusivity of composites at room temperature. The effect of micro- and nanosized fillers on the final thermophysical and electrical behavior is investigated. It was found that the electrical conductivity of composites strongly depends not only on the filler content but also on the filler size. When the microsized graphite was used, the percolation concentration of the filler was found to be 15 vol%, whereas the percolation concentration of the filler in nanocomposites filled with EG of large sizes was significantly lower. Similarly, it was shown that the graphite significantly improves the thermophysical behavior of composites filled with micro- and nanofiller sizes. The thermal conductivity measured values were also compared with some theoretical models for the prediction of the thermal conductivity.