Moisture Dependent Softening Behavior of Wood
Keywords:Viscoelastic behavior, wood, thermal softening, high-temperature, glass transition
An improved understanding of material behavior during the manufacture of wood-based composites can increase the efficiency of wood utilization and provide insight into the development of new processes and products that manipulate the viscoelastic nature of wood. One specific area where additional knowledge can be of great benefit is the influence of heat and moisture on the 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 situ relaxations attributed to the softening of amorphous wood components in the range of 20 to 200°C were observed and found to exhibit the characteristics of a glass transition. The moisture dependence of this transition was characterized, and differences in the observed Tg were detected between juvenile and mature wood. Time-temperature superposition was also shown to be applicable to the wood and water system.
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