KINETIC-MODELS FOR THERMAL-DEGRADATION OF STRENGTH OF FIRE-RETARDANT-TREATED WOOD

Several types of kinetics-based thermal degradation models were evalua ted to predict strength loss of fire-retardant-treated wood as a funct ion of cumulative thermal exposure. The data were taken from previous tests and reports on small, clear specimens of southern pine treated w ith six different fire-retardant chemicals and subjected to various du rations of a steady-state exposure at different temperatures and relat ive humidity levels. We found that the single-stage full model approac h was superior to traditional two-stage approaches. When constrained t o using a two-stage approach, the best alternative two-stage model was a nonlinear model with additive error for each temperature, followed by a weighted regression across temperatures. The advantages of the no nlinear-weighted two-stage model were the maximized fit and more rando m error structure when compared to other two-stage models.