Measurement of dynamic sorption behaviour of small specimens of Pinus radiata - Influence of wood type and moisture content on diffusion rate

Abstract

Sorption behaviour of radiata pine has been investigated by weighing small specimens continuously during isothermal step changes in relative humidity. The use of wood specimens shorter in the longitudinal direction than the average tracheid length of radiata pine ensures that all tracheids in a specimen are exposed, reducing the effect of wood structure on bound water transport. The small size also allows the specimens to be prepared from a single band of earlywood or latewood.

Using the dynamic sorption platform developed at Scion, a number of sorption experiments were undertaken comparing dynamic sorption behaviour of individual bands of earlywood and latewood, which had been heat treated to mimic the chemical changes that occur during high temperature drying.

Diffusion coefficients and surface emission coefficients have been calculated from the sorption data, and are presented here. Earlywood and latewood had different sorption behaviour, but no measurable changes in sorption behaviour were seen with the different heat treatments. Diffusion coefficients were strongly dependent on moisture content.