Kinetic Models for Thermal Degradation of Strength of Fire-Retardant-Treated Wood

Several types of kinetics-based thermal degradation models were evaluated to predict strength loss of fire-retardant-treated wood as a function of cumulative thermal exposure. The data were taken from previous tests and reports on small, clear specimens of southern pine treated with six different fire-retardant chemicals and subjected to various durations of a steady-state exposure at different temperatures and relative humidity levels. We found that the single-stage full model approach was superior to traditional two-stage approaches. When constrained to 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 nonlinear-weighted two-stage model were the maximized fit and more random error structure when compared to other two-stage models