Synergism of GUP and boric acid characterized by cone calorimetry and thermogravimetry

Wood is treated with a new composite flame retardant, whose components guanyl urea phosphate (GUP) and boric acid (BA) impart flame retardance. The flame retarding behavior of these samples is measured by cone calorimeter. The thermal behavior of samples has been studied by differential thermogravimetry (DTG) and thermogravimetry (TG) in air. The activation energies for different stages of thermal degradation are obtained following the method of Broido, A. (1969). J. Polym. Sci., Part 2, 7: 1761. It is found that the combustion parameters of wood, including rate of heat release (RHR) and total heat release (THR) are decreased considerably by the treatment, especially for wood treated with the composite flame retardant of wood (FRW) because of a strong synergistic effect of flame retardance between GUP and boric acid. The mechanism of synergism is explained by analyzing the TG data. The GUP can accelerate dehydration and carbonization while BA can relatively increase thermal stabilization of wood. Their synthetical actions result in more char and less flammable volatile products, obtaining good flame retardance.