Original paper(Vol.45 No.6 pp.687)
Mechanical properties of wood-mineral composites using the water glass-boron compound system
Furuno Takeshi; Aono Shigeo; Uehara Tohru
Abstract:The mechanical properties such as bending strength, hardness, and abrasion resistance of wood-mineral composites were investigated, which were made by introducing inorganic substances into wood using the water glass (sodium silicate)-boron compound system. The heartwood of Sugi (Cryptomeria japonica D. Don) and five kinds of boron compounds were used for the production of the composites. The impregnated specimens were treated with a 5 % acetic acid solution to minimize the influence of alkali in the water glass solution.
The weight percent gains (WPGs) in the composites varied from 20% to 65%, and the WPG values of 10 - 26 % after the leaching procedure were obtained, demonstrating the formation of inorganic substances. The bending strength of the composites showed an increase of 6 - 25 % in comparison with the untreated wood. The increase in the modulus of elasticity was also 16 - 41 %, and it increased lineally with an increase in WPG. On the other hand, the strain at failure became lower than that of the untreated wood, and it had a tendency to reduce as the WPG increased.
The Brinell hardness in the cross section showed a marked increase of 50 - 150% compared with the untreated wood. Because of increasing lineally with an increase in WPG, the enhancement of hardness in the cross section seemed to be due to the filling effect of inorganic substances. On the contrary, the hardness in the radial and tangential sections showed a reduction, and it tended to reduce with an increase on WPG. The reduction of hardness was considered to be closely related to the bulking and the wood deterioration resulting from soaking in an alkaline solution in the wood surface layer.
The Taber type abrasion index in the radial and tangential sections tended to increase with an increase in WPG, showing the reduction of abrasion resistance. This reduction could be also explained by the influence of the bulking and the deterioration owing to alkali.
Key Words:wood-mineral composite, water glass, boron compounds, mechanical properties, bending strength, hardness, abrasion resistance, insoluble inorganic substances, sugi