IMPROVEMENT OF THE FIRE RETARDANCY OF STRANDBOARD BY SURFACE-TREATMENT WITH MELAMINE AND BORIC OR PHOSPHORIC-ACIDS

An effective and simple method of providing fire retardant properties to wood-based materials was developed by the surface coating and subse quent hot pressing of melamine containing fire retardants. The fire re tardants were mixtures of trimethylol melamine and phosphoric acid (TM P) or boric acid (TMB), and those of trimethylol melamine, dicyandiami de, and phosphoric acid (TMDP) or boric acid (TMDB). All chemical form ulations improved the fire retardant performance of strandboards. Both TMB and TMP treatments caused remarkable delays of ignition times whe n coated at 200 g/m(2); however, TMB was more efficient in protecting samples from burning through at the lowest level of treatment. The add ition of dicyandiamide was effective in delaying the burning through t ime for phosphoric acid; however, it improved the fire retardancy in t he early stage of combustion for boric acid. The TMB and TMDB treated strandboards formed uniform charred layers on the surfaces, and the ho mogeneity of the charred layers contributed to homogenous heat distrib ution resulting in better fire retardant properties. Much information on heat distribution and fire retardancy during the testing was obtain ed from a thermographic analysis.