Moisture dependent softening behavior of wood

An improved understanding of material behavior during the manufacture of wo od-based composites can increase the efficiency of wood utilization and pro vide insight into the development of new processes and products that manipu late the viscoelastic nature of wood. One specific area where additional kn owledge can be of great benefit is the influence of heat and moisture on th e softening behavior of wood. The thermal softening behavior of wood at four moisture levels from 0 to 20 % was evaluated using dielectric thermal analysis (DETA). Coincident in sit u relaxations attributed to the softening of amorphous wood components in t he range of 20 to 200 degreesC were observed and found to exhibit the chara cteristics of a glass transition. The moisture dependence of this transitio n was characterized, and differences in the observed T-g were detected betw een juvenile and mature wood. Time-temperature superposition was also shown to be applicable to the wood and water system.