Equilibrium moisture content of wood in high-temperature pressurized environments

Experiments were conducted on the water sorption characteristics of three w ood species, for both juvenile wood and mature wood, at conditions above an d below 100 degreesC. A pressurized chamber was constructed for this purpos e. At 50 degreesC, equilibrium moisture content (EMC) behavior deviated onl y slightly from predictions based on the published data for Sitka spruce. A t 160 degreesC, the sorption behavior was distinctly different from the 50 degreesC data, or any extrapolation from published low-temperature data. Th e data suggested that a change in the sorptive properties of the wood occur red as temperature and moisture conditions exceeded the glass transition te mperature for lignin. At 50 degreesC, juvenile wood tended to equilibrate a t a higher moisture content than mature wood. At 160 degreesC, however, juv enile wood exhibited a markedly lower EMC than mature wood. Thermal degrada tion of wood was detected during the experiments. Reduction in the sorptive behavior as a result of thermal degradation is proposed as a possible expl anation for differences in EMC behavior for juvenile and mature wood at 160 degreesC.