MOKUZAI HOZON (Wood Protection)

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For evaluation of the fire performance of cellulosic materials treated with boron compounds mixed with alkaline metal chemicals, filter paper and Douglas fir veneers were impregnated with them at different chemical weight gains and tested by oxygen index method. Filter paper and veneers were treated by dipping in the aqueous solutions of boron (boric acid) and alkaline metal chemicals (lithium hydroxide, sodium hydroxide and potassium hydroxide) mixed at the molar ratios of 1:0, 1:0.5, 1:1, and 1:2.
The results attained were as follows;
1) The oxygen index of filter paper and veneers could be raised up at higher rate by impregnation with the mixed chemicals of boric acid and alkaline metal hydroxide than each separate chemical, showing additive effects obtained by the combined use of them on suppression of flammability of cellulosic materials.
2) The molar ratios of boron and alkaline metals which showed the best flame-supperssion ability were 1:0.5 for lithium and sodium, and 1:2 for potassium, respectively, at 30% of chemical weight gain.
3) The remarkable additive effects obtained by the combination of boron and alkaline metals were observed for lithium, and then sodium and potassium in the order. The al-kaline metal chemicals with the lower atomic number were assumed to be more effective on the flammability suppression.
4) The treated veneers performed higher values of oxygen index than filter paper at the same weight gains due to chemical treatment, though no significant difference was recognized for untreated ones.
5)The solubility of boron in water could be raised up by mixing with alkaline metals, and the weight gains of the samples due to dipping in the mixed solutions were remarkably increased.

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