Effects of fire retardant chemicals on the bending properties of wood at elevated temperatures.

Fire retardant chemicals are designed to lower the temperature at which thermal degradation occurs. When these chemicals are used for roof sheathing, the combination of chemicals, elevated temperatures, and moisture can sometimes prematurely activate the fire retardant mechanism. The objectives of our study were to determine what kind of fire retardant chemicals are most susceptible to accelerating thermal degradation and at what temperature or temperatures this acceleration occurs. Small, clear Southern Pine specimens were treated with six different fire retardant chemicals and exposed to three environments for up to 160 days. The exposure conditions were (1) 80°F (27°C), 30 percent relative humidity, (2) 130°F (54°C), 73 percent relative humidity, and (3) 180°F (82°C), 50 percent relative humidity. Static bending tests were performed on the treated specimens and untreated controls to determine the effect of treatment and exposure on modulus of