Poplar wood heat treatment: effect of air ventilation rate and initial moisture content on reaction kinetics, physical and mechanical properties

Abstract

The kinetics of heat treatment as well as its effect on some physical and mechanical properties of poplar wood (Populus alba L.) were analysed in this research. Kinetic tests were performed at different treatment temperatures and two different air ventilation settings [low and high air exchange rate (AER) with the exterior]. The treatment kinetics was studied, starting from the oven-dry condition, according to the mass loss during time. The time–temperature equivalency was checked, the mass loss versus time formalised through a master curve. The analysis clearly showed how the heat treatment at low and high AER presents different degradation kinetics even if similar activation energy values were found. Some physical and mechanical properties of wood after treatments up to a mass loss of 7 and 10 % starting from oven-dry or standard environmental conditions state were also studied. All of the treated samples showed statistically significant differences compared to the untreated one. The treatments performed at 7 or 10 % of dry mass loss showed homogeneous behaviour. The same tendency was observed for the treatments starting at oven-dry or standard environmental conditions with the exception of Young’s modulus, which resulted in smaller reductions in wet starting condition when compared to dry samples.