This study was to investigate the high temperature steaming for plastic working of softwood, the property of heat-compressed Pinus radiata wood and the bending process of Pinus densiflora wood as dividing into three chapters. Chapter 1 were studied physical property change, shrinkage change and stre...
This study was to investigate the high temperature steaming for plastic working of softwood, the property of heat-compressed Pinus radiata wood and the bending process of Pinus densiflora wood as dividing into three chapters. Chapter 1 were studied physical property change, shrinkage change and strength property by high temperature steaming from Larix kaempferi wood and property of thermal softening by condition of high temperature steaming from Pinus densiflora wood. In shrinkage changes of high temperature steaming Larix kaempferi wood were used the bomb. The density was decreased with increasing the times and temperatures of steaming. It was considered that the steaming treated specimen's higher shrinkage compared to control was due to change of composition and structure in cell wall. The warpage of half edge grain specimen was decreased by high temperature steaming. Bending strength and compression strength were decreased with increasing the treatment temperatures. Bending modulus was increased with increasing treatment temperatures. But compression modulus was decreased with increasing treatment temperatures. The property of thermal softening by condition of high temperature steaming from Pinus densiflora wood caused by the removal of external resistance of wood by water and heat. The Bending strength and compressive strength along the grain were slightly decreased with increasing the treating temperatures. There was no significant relations between wood strength and steaming temperatures. At the range from 120℃ to 130℃ of steaming temperature, it was considered that the change of composition and structure in cell wall was changed due to release of stresses. Water absorption characteristics were not affected by steaming temperature. In this experiment limits, it was concluded that physical properties of wood by steaming treatment were affected more largely by wood density than by treating temperature. This study of chapter 2 was to investigate the physical properties of Pinus radiata heat-compressed wood by compression condition. Heat-compressed wood is used to improve physical and mechanical properties. In the presence of heat, the objective of wood compression is to increase its physical and mechanical properties and this process might be result in a new material depending on process conditions. Wood color was measured using a colorimeter and evaluated by the NBS(National Bureau of Standards) unit. As a result, the whiteness decreased with increasing compression temperature. In contrast, redness and yellowness was increased with increasing compression temperature. All of the color difference showed the 'Very Much' by NBS unit. The whiteness decreased with increasing compression time. The redness and yellowness were insignificant effect on compression temperature. In other words, the effect of compression temperature was much greater than compression time in the change of wood color. Dimensional recovery test results showed that fixation of compression set improved with increasing compression temperature. However, the fixation effects were negligible by press time. Contact angle increased with increasing press temperature and time. The mechanical properties by compression set were carried out temperature at 180℃ and press time for 60 minutes. The mechanical property of heat-compressed wood increased with increasing compression set. Increase of the specific gravity has led to increase in mechanical property. The maximum compression set of Radiata pine was investigated approximately 65%. It was almost the same result with porosity 68% of Radiata pine in specific gravity 0.48. In case of the mechanical properties by compression temperature and time, the compressive strength and bending strength of heat-compressed wood increased with increasing compression temperature and time. But the compressive strength and bending strength decreased with press temperature 220℃. It was considered due to thermal degradation during high temperature conditions. The surface hardness of heat-compressed wood increased with increasing compression temperature. However, the effect of compression time was negligible. The nail holding power was not affected by compression temperature and time but grain directions. Chapter 3 was to investigate the effect of grain angle, to evaluate the effect of the metal strap thickness and to study the sorption property of steamed wood for bending process from Korean red pine(Pinus densiflora) wood. The density of wood species was the main factor to determine the bending quality. As for relationships between annual ring orientation and metal strap thickness, the bending quality of specimens with intermediate annual ring orientations was better than that of flat-grained specimens in the strap thickness of 1.0㎜ and 0.8㎜, while the reverse result was obtained in the strap thickness of 0.6㎜ and 0.4㎜. These findings suggested that it was important to determine the appropriate strap thickness in relation to wood species, thickness of specimens, form radii and annual ring orientations in specimens. The effect of microwave(2450MHz) irradiation on wood bending was investigated. The specimens irradiated with microwave were bent around a form by using pedestal-steel and clamps. Saturated specimens were boiled in water for an hour. The most suitable time for microwave irradiation seems to range from 60 to 90 seconds. Wood moisture content decreased remarkably with the increase of irradiation time. When a softened wood piece is bent, its convex side was stretched while the concave side was compressed. It can be compressed considerably, but stretched very little. Therefore, the failure will be governed by the tensile breaking strain and occur mainly on the convex face. The thermal treatment of proper temperature and time was suitable for effective dimensional stability of bentwood. The steaming conditions for dimensional stability of bentwoods were 140℃~160℃ of treatment temperature and 20~30 minute of treatment times. In the results of our study, the plastic working of softwood is made possible by decrease of MOE(modulus of elasticity) and plasticization of lignin and hemicellulose from high temperature steaming. In addition, these results showed that the dimensional stability for plastic working of softwood was practicable as a high temperature steaming for hygroscopic degradation on loss of moisture adsorption.
This study was to investigate the high temperature steaming for plastic working of softwood, the property of heat-compressed Pinus radiata wood and the bending process of Pinus densiflora wood as dividing into three chapters. Chapter 1 were studied physical property change, shrinkage change and strength property by high temperature steaming from Larix kaempferi wood and property of thermal softening by condition of high temperature steaming from Pinus densiflora wood. In shrinkage changes of high temperature steaming Larix kaempferi wood were used the bomb. The density was decreased with increasing the times and temperatures of steaming. It was considered that the steaming treated specimen's higher shrinkage compared to control was due to change of composition and structure in cell wall. The warpage of half edge grain specimen was decreased by high temperature steaming. Bending strength and compression strength were decreased with increasing the treatment temperatures. Bending modulus was increased with increasing treatment temperatures. But compression modulus was decreased with increasing treatment temperatures. The property of thermal softening by condition of high temperature steaming from Pinus densiflora wood caused by the removal of external resistance of wood by water and heat. The Bending strength and compressive strength along the grain were slightly decreased with increasing the treating temperatures. There was no significant relations between wood strength and steaming temperatures. At the range from 120℃ to 130℃ of steaming temperature, it was considered that the change of composition and structure in cell wall was changed due to release of stresses. Water absorption characteristics were not affected by steaming temperature. In this experiment limits, it was concluded that physical properties of wood by steaming treatment were affected more largely by wood density than by treating temperature. This study of chapter 2 was to investigate the physical properties of Pinus radiata heat-compressed wood by compression condition. Heat-compressed wood is used to improve physical and mechanical properties. In the presence of heat, the objective of wood compression is to increase its physical and mechanical properties and this process might be result in a new material depending on process conditions. Wood color was measured using a colorimeter and evaluated by the NBS(National Bureau of Standards) unit. As a result, the whiteness decreased with increasing compression temperature. In contrast, redness and yellowness was increased with increasing compression temperature. All of the color difference showed the 'Very Much' by NBS unit. The whiteness decreased with increasing compression time. The redness and yellowness were insignificant effect on compression temperature. In other words, the effect of compression temperature was much greater than compression time in the change of wood color. Dimensional recovery test results showed that fixation of compression set improved with increasing compression temperature. However, the fixation effects were negligible by press time. Contact angle increased with increasing press temperature and time. The mechanical properties by compression set were carried out temperature at 180℃ and press time for 60 minutes. The mechanical property of heat-compressed wood increased with increasing compression set. Increase of the specific gravity has led to increase in mechanical property. The maximum compression set of Radiata pine was investigated approximately 65%. It was almost the same result with porosity 68% of Radiata pine in specific gravity 0.48. In case of the mechanical properties by compression temperature and time, the compressive strength and bending strength of heat-compressed wood increased with increasing compression temperature and time. But the compressive strength and bending strength decreased with press temperature 220℃. It was considered due to thermal degradation during high temperature conditions. The surface hardness of heat-compressed wood increased with increasing compression temperature. However, the effect of compression time was negligible. The nail holding power was not affected by compression temperature and time but grain directions. Chapter 3 was to investigate the effect of grain angle, to evaluate the effect of the metal strap thickness and to study the sorption property of steamed wood for bending process from Korean red pine(Pinus densiflora) wood. The density of wood species was the main factor to determine the bending quality. As for relationships between annual ring orientation and metal strap thickness, the bending quality of specimens with intermediate annual ring orientations was better than that of flat-grained specimens in the strap thickness of 1.0㎜ and 0.8㎜, while the reverse result was obtained in the strap thickness of 0.6㎜ and 0.4㎜. These findings suggested that it was important to determine the appropriate strap thickness in relation to wood species, thickness of specimens, form radii and annual ring orientations in specimens. The effect of microwave(2450MHz) irradiation on wood bending was investigated. The specimens irradiated with microwave were bent around a form by using pedestal-steel and clamps. Saturated specimens were boiled in water for an hour. The most suitable time for microwave irradiation seems to range from 60 to 90 seconds. Wood moisture content decreased remarkably with the increase of irradiation time. When a softened wood piece is bent, its convex side was stretched while the concave side was compressed. It can be compressed considerably, but stretched very little. Therefore, the failure will be governed by the tensile breaking strain and occur mainly on the convex face. The thermal treatment of proper temperature and time was suitable for effective dimensional stability of bentwood. The steaming conditions for dimensional stability of bentwoods were 140℃~160℃ of treatment temperature and 20~30 minute of treatment times. In the results of our study, the plastic working of softwood is made possible by decrease of MOE(modulus of elasticity) and plasticization of lignin and hemicellulose from high temperature steaming. In addition, these results showed that the dimensional stability for plastic working of softwood was practicable as a high temperature steaming for hygroscopic degradation on loss of moisture adsorption.
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