This experiments were carried out to know the mechanical properties of the plywood treated with two fire retardant chemicals and the untreated plywood. In this study, a special grade of defect-free, Southern pine plywood was used. Specimens were cut into 15- by 60-cm dimensions from 120-by 240-cm panel. Two group’s specimens were treated with chemicals: guanylurea phosphate/boric acid(GUP /B) and monoammonium phosphate(MAP). The chemicals were pressure impregnated using a full-cell pressure process and concentration of the treating solution was adjust ε d to give approximately 1.58 kg/(30cm)³ retention. Two other specimens were used for untreated controls. After treatment, the specimens were dried in a kiln under varying mild drying conditions. After redrying, specimens were exposed to a 24hr cycle consisting of 14hr at 26.6 C, followed by 2hr of ramping the temperature to 65 C, maintained at 65 C for 7hr, then ramped down to 26.6 C for 1hr, and duration times for the exposures were 0,21,60, 160 and 400 days for the 12% equilibrium moisture content exposures. Afrer removal from the environmental chambers, specimens were weighed and reconditioned to constant weight at 23 C and 65% relative humidity prior to bending tests. After conditioning, treated and untreated specimens were tested for bending stiffness and strength using the general procedures to determine modulus of elasticity (MOE), modulus of rupture (MOR) and work to maximum load(WML). The results were summarized as follows; 1. The MOE values for th ε 12% moisture content were a significant difference at the 5% level between the treated specimens and the controls, but not between the two treatment groups. The untreated controls have higher MOE values than the two fire retardant chemicals by approximately 5 to 10%. 2. The MOR values have a slight negative trend during exposure, but the trend was not statistically different for the two treatments. The MOR values for the two treatment groups were approximately 15 to 20% lower than those of th ε untreated controls 3. The most effected strength property was work to maximum load. Treated specimens showed a greater tendency for degrade than did untreated specimens. The monoammonium phosphate treatment appeared to be more susceptible to degrade than did the guanylurea phosphate/boric acid.
1.緖言
2.材料 및 方法
3.結果 및 考察
4.結論
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