Thermal conductivity of high density polyethylene: Cold plasma modified graphite composites

Abstract Natural graphite particles (NG) were surface modified via ethylene plasma treatment and characterized by infrared and Raman spectroscopy, thermo‐gravimetric analysis, scanning electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. Ethylene polymerized during plasma treatment forming both a thin layer on the graphite particles surface and polyethylene particles that penetrate into the graphite layers, favoring its delamination or exfoliation. This beneficial effect finally impacts in the thermal properties of the composites: in fact, thermal conductivity (k) determined via modulated differential thermal calorimetry is, in general, larger than that of the pure polyethylene because of the graphite contribution and, with a major increase for graphite composites obtained with the treated than untreated NG because of the better dispersion.