Effect of temperature on electrical conductivity of green sapwood of Pinus radiata (radiata pine)

Joule heating of green Pinus radiata, if controlled in a range 60–90 °C, has the potential to be used for veneer cutting, improving the peeling process and the quality of veneer. This research attempts to study the wood’s electrical conductivity, one of the key variables in controlling the Joule heating effect. Electrical conductivity of green New Zealand grown radiata pine sapwood was studied over a 20–90 °C temperature range. The sapwood studied had moisture content in the range of 100–200%. The effects of wood parameters such as grain orientation, moisture content, and basic density were evaluated. The effects of temperature and grain orientation on the conductivity were found to be much greater than those of moisture content and basic density. At 23 °C, conductivity in the longitudinal direction was around 20 times higher than in the tangential and 10 times higher than in the radial direction. Between 23 and 90 °C the longitudinal conductivity increased threefold, near linearly with temperature, whereas the tangential and radial conductivities increased nonlinearly by factors of 6 and 4, respectively. A statistical model based on the experimental results has been developed using the linear mixed effect model.