Properties of thermally modified medium-density fibreboards

Thermal treatment of solid timber and oriented strandboards (OSB)improves durability against fungal decay and dimensional stability (swelling and shrinking). It is not clear whether thermal treatment of medium-density fibreboards (MDF)has the same effects. In this work, four variants of phenolformaldehyde (PF)-bonded MDF with varying contents of resin and hydrophobing agent were thermally post-treated according to the Mühlböck procedure at three different maximum temperatures. The short-term properties internal bond, modulus of rupture, modulus of elasticity, thickness swelling and equilibrium moisture content and the long-term property creep behaviour of treated variants and of one untreated variant have been tested. The results are presented and discussed in comparison with the respective European standards. Altogether, the thermal treatment had a positive effect on most of the tested mechanical short-term properties. The moisturerelated properties, i.e., thickness swelling and equilibrium moisture content, were also positively influenced. The creep behaviour of heat-treated MDF could also be improved by thermal modification.