The effect of synthetic and natural fire-retardants on burning and chemical characteristics of thermally modified Padouk (Pterocarpus soyauxii) wood

This article focuses on flammability and different modification temperatures on selected combustion characteristics and chemical components determined for teak wood (Pterocarpus soyauxii L. f.). The ThermoWood R principle has been used to modify thermally at 160 ◦C, 180 ◦C, and 210 ◦C. After the thermal modification the wood was treated with an immersion process of the wood specimen with ammonium phosphate-based synthetic flame retardant and arabinogalactan based natural flame retardant. Subsequently combustion parameters such as maximum combustion speed, combustion speed, weight loss, the ratio between maximum combustion speed and time to reach maximum combustion speed together with the effect of thermal modification and flame retardant were measured. The chemical variations of wood have been considerable with large variations in cellulose, hemicellulose, holocellulose, lignin and extractives content. Spearman’s correlation was used to study the relationship between chemical changes and combustion characteristics. The results showed that the thermal modification of padauk wood damaged its combustion and ignition properties. After impregnation with the high-quality retardant, the effect of the thermal modification was eliminated. The relative content of lignin, cellulose and extractives had an increase, while the amount of holocellulose and in particular hemicellulose had a decrease.