Management and Economics wood
Reza Jazayeri; Reza Hajihassani; Sedighe Nazari
Abstract
The main purpose of this study was to evaluate the effect of hydrothermal treatment with boric acid impregnation on some physical and mechanical characteristics and fire resistance of poplar (Populus nigra) and radiata pine (Pinus radiata) wood. In this study, two times of 60 and 90 minutes with two ...
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The main purpose of this study was to evaluate the effect of hydrothermal treatment with boric acid impregnation on some physical and mechanical characteristics and fire resistance of poplar (Populus nigra) and radiata pine (Pinus radiata) wood. In this study, two times of 60 and 90 minutes with two temperatures of 150○C and 180○C were used for the hydrothermal treatment, and boric acid with concentrations of 1, 3 and 5% dissolved in water used for the impregnation treatment. The measurement of the characteristics, including bending strength, impact resistance, volumetric swilling and fire resistance (weight loss due to fire) were done by ASTM-D143, ASTM-D256, ASTM 4446-2002 and ISO 11925 standards, respectively. About fire resistance, 5% boric acid treatment showed the least weight loss due to burning in the wood of two species. As a result of the hydrothermal treatment alone, the fire resistance was even lower than the control. In this regard, the combination of hydrothermal treatment with boric acid treatment resulted in results close to those of hydrothermal with boric acid treatment. Positive effect of hydrothermal treatment on the improvement of dimensional stability, is considered as one of the results of the present study. The temperature of 180○C with a time of 90 minutes reduced the swelling of poplar and radiata pine by about 36.8 and 42%, respectively. Regarding impact resistance, the effect of hydrothermal treatment on the wood of both species and the effect of boric acid treatment on radiata pine wood were negative. Hydrothermal treatment at a temperature of 180○C and with a time of 90 minutes decreased the impact resistance by 28.2% in the wood of both species, and 5% boric acid treatment caused a 13.3% decrease in this property in radiata pine wood.
Mechanical conversion of wood and wooden fittings
Mostafa Poozesh; Hamid Reza Mansouri; babak Nosrati; Alireza Samzadeh
Abstract
This objective of this investigation was to modify and improve the water resistance of urea formaldehyde (UF) bonded particleboard adding Boric acid to the resin. Four levels (1, 2, 3 and 4) of boric acid based on the dry weight of the bonder were added to the UF resin. Then these mixtures were ...
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This objective of this investigation was to modify and improve the water resistance of urea formaldehyde (UF) bonded particleboard adding Boric acid to the resin. Four levels (1, 2, 3 and 4) of boric acid based on the dry weight of the bonder were added to the UF resin. Then these mixtures were used to produce particleboard. Physical and mechanical properties were examined according to the ASTM, D1013-04. The results showed that the using of this additive increased the water absorption and thickness swelling resistance after 2 and 24 hours immersion in water. Also using this additive increased the internal bonding of the boards after 24 hours after immersion in water, compared to the control sample but in the case of dry samples, the internal bonding decreased compared to the control sample. However it was not lower than standard value. As the Boric acid levels increased to 2 percent, bending strength of the samples was increased compare to the control sample and after this level it was decreased. Also with increasing the levels to 4 percent, modulus of elasticity of boards were increased compare to the control sample
