Time/temperature equivalence in the dry wood creep response

Abstract

Abstract Rheology of wood molecular and supramolecular organization has mostly been conducted with dynamic methods, and the application of time/temperature equivalence typically requires plasticizers to observe segmental relaxation. Dry wood rheology offers the experimental advantage of easy moisture control, but only weak secondary relaxations are observed with dynamic methods. Static methods allow for the longer relaxation times in glassy polymers, and these relaxations are strongly stimulated by lower less damaging temperatures. This study describes the application of creep mode time/temperature equivalence to dry yellow-poplar (Liriodendron tulipifera) and southern yellow pine (Pinus spp.). It was found that time/temperature equivalence was valid from 10–170°C, but only for specimens that received a prior 30-min thermal treatment (with minor desiccation) in the range of 100–170°C. The two woods exhibited clear differences in the temperature dependence of the dry wood creep relaxation, and in the sensitivity to free volume manipulation. These findings are believed to reflect polymer structural differences in hardwoods and softwoods indicating that creep mode time/temperature studies of dry wood may be useful for the analysis of xylem polymer behavior.