PARTICLEBOARD HYGROSCOPICITY - ITS PREDICTION AND THE INFLUENCE OF HOT-PRESSING

As part of a systematic study for an understanding of the hygroscopici ty of wood-based panel products, the effect of hot-pressing on wood-pa rticle hygroscopicity was investigated. The equilibrium moisture conte nt (EMC) of hot-pressed particles ranged from 73% to 93% of non-hot-pr essed particles, and was found to be related closely to the maximum te mperature reached during pressing. There was a tendency for particle h ygroscopicity to decrease as acidity and crystallinity increased. The hot-pressing also caused particle colour change, which was closely rel ated to the changes in hygroscopicity. By combining adsorption isother ms of the heated particles and binders, the EMCs of panels were predic ted. The differences in EMC between the surface and the core lawyers w ere found to be greatest at low relative humidities; the differences b ecoming negligible above 80% relative humidity. Each panel EMC predict ed was less than the EMC of the non-hot-pressed particles.