Effects of various fire retardant (FR) chemicals on mechanical and fire properties of plywoods were investigated. Boron compounds such as, borax and boric acid; and phospate compounds such as, monoammonium phosphate and diammonium phospahate were used as fire retardant chemicals in the plywood panels. An exterior liquid phenol formaldehyde resin with 47% solids content was used as adhesive. The 2.2 mm thick Tetraberlina wood veneers were treated with the liquid solution of FR chemicals. The plywoods having 5-layers were produced from the treated wood veneers. The mechanical properties of the plywoods produced with treated veneers was found to be lower than that of the control group. Among the treated plywoods, The plywoods treated with borax had highest mechanical properties, followed by diammonium phosphate (DAP), monoammonimum phosphate (MAP), and, boric acid, respectively. The FR chemicals improved the fire resistance of the plywoods. The chemicals showed individually different effects related to improvement of fire resistance of the panels. For example, the OSB panels treated with diammonium phoshate were the latest ignited group (52.8 s) which were followed by the panels treated with boric acid (49.2 s), borax (44.5 s), and monoammonium phosphate (41.2 s), respectively. As compared to the control group (7.5 cm), the plywoods treated with borax (3.6 cm) had the shortest flame length after burner was turn off, followed by diammonium phosphate (4.2 cm), boric acid (5.1 cm), and monoammonium phosphate (5.8 cm).
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