Effects of furfurylation on interactions between moisture sorption and humidity conditioning of wood

To investigate effects of furfurylation on interactions between moisture sorption and humidity conditioning of wood, Pinus spp. wood was impregnated with furfuryl alcohol solution. After oven drying, furfurylated wood and untreated wood were subjected to two environments where initial relative humidity (RH) was, respectively, about 60% and 80% at 25 °C. Dynamic mass and RH were continuously recorded with a self-assembled device. Furfural resin polymerized in cell walls, cell lumina and some pits, which caused mass gain and cell wall bulking. Furfurylation weakened humidity conditioning performance and hygroscopicity of wood, and the RH increased by over 20.7% while moisture content decreased by over 33.6% for furfurylated wood compared to untreated wood after conditioning at initially about 80% RH. Humidity conditioning process was generally divided into four stages according to changing rate, where RH exhibited sharp increase, slow increase, slight decrease and sub-equilibrium, respectively. Moisture content showed a negative linear relation with RH in the first three stages. This was a result of combined effects of the pressure from water vapor gradient and moisture content gradient, the temperature changes during sorption, the hindrance from capillary systems and attraction of other water molecules. The interaction rate between humidity conditioning and moisture sorption was decelerated for blocking of water passages, reduction in sorption sites and hydrophobicity increase due to furfurylation. Over 45.2% decrease in moisture change rate with RH was caused by furfurylation in the first stage. The study can help in understanding the effects of furfurylation on interactions between moisture sorption and humidity conditioning of wood and facilitate better application of modified wood in human settlement practically.