Thermal conductivity of flat-pressed wood plastic composites at different temperature and filler content

The thermal conductivity of wood flour (WF) filled high density polyethylene composites (wood plastic composite, WPC) is investigated experimentally as a function of filler content and temperature. Samples are prepared by compression molding process of previously blended and extruded WPC pellets, up to 50% weight content of WF. The thermal conductivity is measured by the heat flow meter technique in a temperature range from 15°C to 80 °C. Experimental results show that the WPC thermal conductivity decreases with temperature and WF content, with the last effect due to the increase in porosity with the filler content, as confirmed by density measurements. Using the thermal conductivity of bare WF, the thermal conductivity of the wood material in WPC (WM) is estimated. This value successfully predicts the upper and lower bounds of the WPC thermal conductivity by means of the parallel and series conduction model of a multi-phase composite material.