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© 2018, The Japan Wood Research Society. Transmittance and reflectance of visible light by sugi wood (Cryptomeria japonica) were investigated in the longitudinal (L) and tangential (T) directions. Transmittance was the highest in the L direction and reflectance was the highest in the T direction, suggesting that structural anisotropy influences transmittance and reflectance. Intra-ring variations observed with a microspectrometer indicated that T transmittance was higher for latewood than for earlywood, but there was no such trend in for L transmittance in which the highest levels occurred near the annual ring boundaries, on either the earlywood or latewood side, and the lowest at the transition from earlywood to latewood. Dependence of L transmittance on wavelength also showed variations according to the intra-ring position. The increasing of transmittance of earlywood at wavelengths < 500 nm with increasing wavelength was observed, but this was not confirmed for latewood because of absorption by lignin. These observations supported a previously published finding, which was based on measurements in the radial direction, that the number of internal cell wall reflections, rather than density, determines wood lightness. Indeed, in the L direction, most of the incident light passes through lumens in earlywood and through cell walls in latewood, while it is subjected to numerous internal reflections at the interface between lumens and cell walls. This was further confirmed by the transmittance of earlywood being greatly decreased by radial compression.

DOI： 10.1007/s10086-018-1751-7

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Language：Japanese   Publisher：The Japan Wood Research Society  

<p>To investigate the relationship between reflection and transmission intensities in the visible light region of wood, total light transmittance and total reflectance of sugi samples compressed at various compression rates were measured. Before compression, samples were impregnated with low molecular weight phenolic resin in order to maintain compressive deformation. Regardless of the rate of compression, both reflection and transmission were low in the short wavelength region. In the long wavelength region, the transmittance of the sample increased when exceeding the rate of compression to reduce lumen volume to less than 30% of initial volume, but the reflection of these samples decreased. These effects were not related to sample weight. This result contradicts the theory, proposed by Kataoka, that the transmission depends on the absorption of light. We checked the relationship between transmittance and reflection. We could confirm that the relationship is inversely proportional. Therefore, we presume that the amount of reflection within wood is important to transmit light in the long wavelength region. Assuming a model where the diameter of the cell is 30µm and the refractive index of the cell wall is 1.6, there is strong agreement between the model and measured data in terms of the relationship between transmission and thickness. These results suggest that the reflection of light, that is, the lightness of wood, not only depends on density but also more on the amount of reflections in the layer, especially at long wave lengths.</p>

DOI： 10.2488/jwrs.64.66

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

© 2016 Author(s). We have developed novel wood composite with optical transparency at arbitrary region. Pores in wood cells have a great variation in size. These pores expand the light path in the sample, because the refractive indexes differ between constituents of cell and air in lumen. In this study, wood compressed to close to lumen had optical transparency. Because the condition of the compression of wood needs the plastic deformation, wood was impregnated phenolic resin. The optimal condition for high transmission is compression ratio above 0.7.

DOI： 10.1063/1.4949710

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WALTER DE GRUYTER GMBH  

The thermal expansion behavior of dry solid wood was investigated by dynamic dilatometry and thermal mechanical analysis. Anomalous thermal expansion behavior was observed concerning the displacement change under a constant compression pressure, which was not previously reported. Wood submitted to temperatures below 0 degrees C under dry conditions exhibited a large increment in the linear thermal expansion coefficient (CLTE) and a sudden drop in the CLTE around 50 degrees C as well as above 130 degrees C during heating. In subsequent cooling/heating processes, these anomalous behaviors remained at temperatures below 100 degrees C, although less pronounced, and disappeared at temperatures above 100 degrees C. These behaviors were clearly perceptible in the radial and tangential directions but not in the longitudinal direction. The CLTE depended strongly on the heat and moisture history of the samples and the effects are species-specific.

DOI： 10.1515/hf-2013-0103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INDERSCIENCE ENTERPRISES LTD  

In order to facilitate the generation of a flow phenomenon due to the slipping of wood cells under a specific temperature condition, a phenol formaldehyde resin of low molecular weight was introduced into wood cells. The effects of the presence of phenol formaldehyde molecules in wood cells on the flow behaviour of solid wood were investigated experimentally by means of a free compression test. The effectiveness of using phenol formaldehyde resin as an adsorbent to act as both binding and plasticising agents in the proposed wood flow forming shaping technique was examined, and an application to wood flow forming was demonstrated. The results revealed that the flow phenomenon of solid wood occurred at a certain resin content, even under compression at less than 25 MPa. An increase in the moisture content led to further improvement of the flowability of solid wood, which resulted from weakened facial strength among wood cells and intercellular layers due to a local increase in the volume of nano-level pores. Finally, the effectiveness of introducing phenol resin into wood for wood flow forming through backward extrusion was confirmed.

DOI： 10.1504/IJNT.2014.060572

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Language：English   Publisher：Springer  

Friction that arises during processing for the deformation of wood under relatively high pressure levels (ca. &gt; 1 MPa) is an important factor to be taken into account when wood is processed. However, few studies on such friction have been published. The present study was undertaken to evaluate the influence of surface finishing conditions on the nominal friction coefficient (mu) of the wood and metal tool surfaces. Sticking friction was likely to arise on a relatively coarse metal surface, and the type of metal tool surface finishing was found to have large impact on the friction mechanism. The friction characteristics during exposure to high pressure seem to be affected not only by the interface contact characteristics, but also by the deformation characteristics of wood during compressive load or measurement. The value of mu on water-saturated wood was equal or higher than that on dry wood, which suggests that the contact characteristics between these two types of wood are significantly different. The water content in wood was shown to affect both the interface contact and deformation characteristics of wood. The value of mu was not significantly affected by the wood surface finishing conditions; however, changes in mu during sliding differed slightly, depending on the finishing conditions.

DOI： 10.1007/s10086-012-1295-1

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Language：Japanese   Publisher：The Japan Wood Research Society  

Friction between wood and metal is an important factor in the wood deforming process. To investigate the friction characteristics under high pressure conditions (above 1MPa) which are generated during deforming processing, we examined the influence of the moisture content of wood. The friction coefficients were measured in various normal loads <i>N</i> (1, 5, 10kN). The value of friction coefficients during sliding (<i>&mu;</i>_s) increased with moisture content of the wood sample. <i>&mu;</i>_s of water swollen wood decreased since water acts as a lubricant. <i>&mu;</i>_s decreased by the wood deformation. However, <i>&mu;</i>_s increased as the wood was more compressed. These results suggested that the friction characteristics during exposure to high pressure are greatly affected by deformation characteristics of wood. On the other hand, it appeared that <i>&mu;</i>_s affected the wood deformation.

DOI： 10.2488/jwrs.58.302

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Enthalpy relaxation of dry wood has been investigated by temperature-modulated differential scanning calorimetry. The reversing and non-reversing heat flow changes revealed that enthalpy relaxation occurred in dry wood, which did not exhibit any clear glass transitions. This enthalpy relaxation behavior seemed to differ significantly from those of previously reported isolated lignins, which implies that the microstructure of dry wood possesses a rigid amorphous state derived from interactions among wood components. The observed enthalpy relaxation is considered to be related to other components besides lignin, and the time-dependent physical properties due to unstable states or physical aging of wood originate not only from lignin but also from other components, such as cellulose and hemicellulose and the interactions between them.

DOI： 10.1007/s10086-012-1264-8

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The thermal properties and transitions of solid and ground wood samples conditioned at different humidity conditions were investigated by temperature-modulated differential scanning calorimetry. A time-dependent transition was detected as an endothermic peak in the total and non-reversing heat flows and as a step change in the reversing heat flow during the first heating run of samples with moisture contents above 5 %, but it disappeared in the second heating run. These different thermal behaviors indicate that the effect of heat and moisture on the thermal properties of wood is history dependent. This step change in the reversing heat flow is considered to be a glass transition of moist wood. Other relaxation processes (e.g., enthalpy relaxation) occur simultaneously with this glass transition. The temperature ranges of the transition and the relaxation decreased drastically as the moisture content increased up to 11 %, while they remained almost constant at higher moisture contents. In addition, the transitions of the ground wood occurred at lower temperatures than those of the solid wood at similar moisture contents. Kissinger plots revealed that the apparent activation energy for the glass transition of the solid wood with a moisture content of 11 % was about 600 kJ/mol, whereas that of the ground wood was 220 kJ/mol.

DOI： 10.1007/s10086-012-1259-5

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Language：Japanese   Publisher：The Society of Materials Science, Japan  

To investigate the friction characteristics between wood and metal tool under high pressure conditions, we analyzed the nominal friction coefficient between them in various normal pressures (1.1&sim;11MPa). The effects of anisotropy of wood were examined by changing friction surfaces and sliding directions of wood samples. The wood samples were slid about 10mm. The results showed as follows. 1) The nominal friction coefficient behaviors varied according to normal loads and friction surfaces or sliding directions of the wood samples. 2) In longitudinal compression conditions, the nominal friction coefficient could be considered that there were no effects of the normal loads. In tangential or radial compression conditions, the nominal friction coefficient decreased as the normal load increased. The nominal friction coefficients of longitudinal direction were larger than that of radial direction in the edge grain friction surface. 3) By observation of friction surfaces after sliding, it appears that the nominal friction coefficients were more influenced by deformation force in the wood sample.

DOI： 10.2472/jsms.61.335

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Language：Japanese   Publisher：社団法人日本材料学会  

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Language：Japanese   Publisher：The Japan Society for Technology of Plasticity  

Various global environmental problems are caused by the volume consumption of fossil resources. As a solution to these problems, the development of wood plastic composites (WPC) and natural fiber reinforced plastics (NFRP) as substitutes for oil-based plastic is being furthered. However, the investigation of the environment resistance of injection molding products made from only wood-based material as a basic study of WPC and NFRP has not been carried out. In this study, a basic examination of resistance to water, heat-drying and light was performed on injection molding products made from only steamed bamboo powder. The results show that the products did not deteriorate after soaking in water for two weeks. Sectional area and weight increased after soaking in water, but they decreased by more than 10% after air-drying. Vickers hardness decreased after soaking in water, but it recovered after air-drying. Heat-drying at 80℃ for two weeks did not change the appearance of the products markedly. However, shrinkage between 4% and 8% was observed and weight decreased by about 5%. On the other hand, Vickers hardness and bending strength increased. By irradiation with ultraviolet rays, the color and shape of the products did not change markedly, but brightness markedly increased.

DOI： 10.9773/sosei.53.826

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To investigate the effect of drying time on the thermal behavior as well as the dynamic viscoelastic behavior of wood, thermal analyses such as modulated temperature differential scanning calorimetry (MT-DSC), thermal gravimetry (TG) and dynamic mechanical analysis (DMA) were performed under a similar temperature schedule in which three times cyclical heating and cooling processes between 105 and 180°C was conducted after drying at 105°C for from 15 to 960 min. Results obtained showed as follows. 1) From the TG measurements, mass losses were hardly recognized during drying and heating-cooling processes, whereas heat flows in the first heating process of the DSC measurements showed different behaviors. The heat flow got exothermic around 140°C compared with those of the second and third heating processes. The beginning of the exothermic behavior showed at a higher temperature when the drying time set longer. The release of some amounts of energy seen as an exothermic behavior during the first heating could be believed that finestructure of wood changed to a lower energy level, and it was thought that a longer drying time resulted in a lower energy level in the finestructure of wood which was likely observed in an enthalpy relaxation of a glassy polymer during annealing. 2) Dynamic heat capacities obtained from MT-DSC measurements showed different behaviors in the first heating process, and it was slightly larger than those of the second and third heating processes. For a longer dry time, the dynamic heat capacity was decreased at temperatures lower than about 150°C. This decreased heat capacity suggested a packing of finestructure occurred during the first heating. 3) tanδ from DMA measurements showed a similar temperature dependency to the dynamic heat capacity, and this supported the finestructure change of wood deduced from the DSC results.

DOI： 10.2472/jsms.60.300

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Relationship between thermal-softening properties and deformation appearing after heating and cooling processes with loading was investigated. In the heating process, an obvious decrease in relative relaxation modulus due to thermal-softening of lignin was found at around 60 degrees C. After the cooling process, around 70% of residual deformation was measured. Also, the residual set depended on the maximum temperature reached in the heating process and the unloaded temperature in the cooling process. It was thought that these results suggest that the glass transition of lignin from the rubbery to glassy state is important to fix the deformation. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.energy.2010.02.035

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To obtain new information about destabilization of wood microstructure caused by drying, effects of drying history on physical properties of wood were studied using the measurements of dynamic viscoelastic properties and gas adsorption. First, dynamic viscoelastic properties of dry wood in the radial direction were measured between 100°C and 200°C. Unstable states of dry wood still existed after heating at 105°C for 30 min and were modified by activated molecular motion in the first heating process to higher temperatures above 105°C, and dry wood subjected to higher temperatures showed larger dynamic elastic modulus (E′) and smaller loss tangent (tan δ). The phenomena thought to be caused by the unstable states reappeared after wetting and drying again. Secondly, carbon dioxide adsorptions onto dry wood at ice-water temperature (273 K) were measured, and micropore size distributions were obtained using the Horvath-Kawazoe (HK) method. Micropores smaller than 0.6 nm exist in dry wood. They decreased with elevating drying temperatures from 50°C to 160°C and increased again after rewetting and drying. In conclusion, it was confirmed that wood components in the microstructures were destabilized by drying and that physical properties of dry wood changed with drying histories. © 2011 Taylor &amp
Francis.

DOI： 10.1080/17480272.2010.551545

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Language：Japanese   Publisher：The Society of Materials Science, Japan  

In a production of compound-type wood plastic composite (WPC), hydrophobic treatments of wood elements were expected to improve interfacial adhesion between hydrophilic woods and hydrophobic plastics. However, some of results obtained by such process did not show improvements on mechanical properties of resultant products. This difference in an effectiveness of hydrophobic treatments of wood seemed to be caused by the mixing and compounding conditions for treated woods and plastics used in previous studies. There were a few studies focused on the mixing condition in WPC productions for treated wood elements. From these points of view, WPC was prepared from hydrophobized wood flour by acetylation (A-WF) and commercialized polypropylene (PP) to investigate the mixing properties as well as the mechanical properties. A blend of wood flour with PP in same weight was compounded in a closed mixing blender under the condition that mixing time was varied from 5 to 30 min at a constant temperature of 180&deg;C with a constant blender revolution of 30rpm. The mixing properties were evaluated by measuring the torque change during the mixing and the dispersion state of the untreated/treated wood flour in the PP compounded in each mixing time. As evaluation of the mechanical properties, the static bending modulus and the impact strength were measured. Results were summarized as follows; 1) It was found from microscopic observations that A-WF has poor dispersiveness than that of the untreated wood flour. 2) By increasing mixing time, the flexural modulus of the WPC tended to be slightly decreased, although the impact strength was obviously improved. 3) By the SEM examination, the A-WF improved interfacial wetting between the wood flour and the PP and increased mutual contact surface by deformation due to softening in the mixing temperature. From the results, it appeared that dispersiveness was changed by hydrophobization of wood and the mechanical properties were consequently affected by this change.

DOI： 10.2472/jsms.60.306

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A large deformation of bulk wood using slipping between the wood cells has been found just like a plastic deformation generated by slip band in metallic materials. This phenomenon is caused by the hierarchical structure of the wood cell, and the intercellular layer becomes selectively softened in moistened states of wood. In such conditions, bulk wood subject to compression at elevated temperatures can easily be deformed perpendicular to the longitudinal direction of the cells by shear flow stress after being collapsed. © 2011 Materials Research Society.

DOI： 10.1557/opl.2011.609

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Language：Japanese   Publisher：The Society of Materials Science, Japan  

To investigate the effect of drying time on the thermal behavior as well as the dynamic viscoelastic behavior of wood, thermal analyses such as modulated temperature differential scanning calorimetry (MT-DSC), thermal gravimetry (TG) and dynamic mechanical analysis (DMA) were performed under a similar temperature schedule in which three times cyclical heating and cooling processes between 105 and 180&deg;C was conducted after drying at 105&deg;C for from 15 to 960 min. Results obtained showed as follows. 1) From the TG measurements, mass losses were hardly recognized during drying and heating-cooling processes, whereas heat flows in the first heating process of the DSC measurements showed different behaviors. The heat flow got exothermic around 140&deg;C compared with those of the second and third heating processes. The beginning of the exothermic behavior showed at a higher temperature when the drying time set longer. The release of some amounts of energy seen as an exothermic behavior during the first heating could be believed that finestructure of wood changed to a lower energy level, and it was thought that a longer drying time resulted in a lower energy level in the finestructure of wood which was likely observed in an enthalpy relaxation of a glassy polymer during annealing. 2) Dynamic heat capacities obtained from MT-DSC measurements showed different behaviors in the first heating process, and it was slightly larger than those of the second and third heating processes. For a longer dry time, the dynamic heat capacity was decreased at temperatures lower than about 150&deg;C. This decreased heat capacity suggested a packing of finestructure occurred during the first heating. 3) tanδ from DMA measurements showed a similar temperature dependency to the dynamic heat capacity, and this supported the finestructure change of wood deduced from the DSC results.

DOI： 10.2472/jsms.60.300

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To investigate micropores and mesopores in the cell walls of dry wood, CO2 gas and N-2 gas adsorption onto dry wood were measured at ice-water temperature (273 K) and liquid nitrogen temperature (77 K). CO2 gas adsorption isotherms obtained were used for determining micropore volumes smaller than 0.6 nm by the HK method (Horvath-Kawazoe method), and N-2 gas adsorption isotherms obtained were used for determining the mesopore volume between 2 nm and 50 nm by the Barrett-Joyner-Halenda (BJH) method. Micropores and mesopores existed in cell walls of dry wood, and the cumulative pore volume was much larger for micropores than for mesopores. Micropores in the cell wall of dry wood decreased with elevating heat treatment temperature, and the decreased micropore was reproducible by wetting and drying. Mesopores did not decrease so much with elevating heat treatment temperature. Micropore volumes for the softwood Hinoki and the hardwood Buna were compared. A larger amount of micropores existed in hardwood Buna than in softwood Hinoki, and this relationship was considered to correspond to the difference in thermal softening properties for lignin in water-swollen Hinoki and Buna. This result probably indicates that micropores in the cell walls of dry wood relate to the structure of lignin.

DOI： 10.1007/s10086-009-1063-z

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

In this study, wood (cedar) powder ranging from 53 &micro;m to 1 mm sizes, recycled polypropylene (PP) / polyethylene (PE) and acid-modified PP as a compatibilization agent were used to produce a wood-plastic recycled composite (WPRC). For discussing the effects of the wood powder sizes on the mechanical properties of the WPRC, a mixing process of the wood powder and the plastics in a constant wood content of 50% weight was firstly performed by a mixing machine controlled temperature and rotation of mixing blade. And then, to obtain WPRC panels the wood and plastics mixtures were compressed in a mould under a constant pressure and a temperature for a certain holding time. WPRC specimens for mechanical tests were cut from the WPRC panels, and a tensile strength and a size-stability were acquired. The results show that the successful mixing process runs above 180&deg;C, where the mixing torque required compounding keeps constant or slightly increases. The tensile strength of the WPRC increases when the smaller size of wood powder is used for wood/plastic compound under successful mixing conditions. It is shown from thickness change rate of specimens that mixing temperature of wood/plastic compound affects a size stability of the WPRC.

DOI： 10.1299/jmmp.3.624

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Water is an essential part of the structure of biological materials. To estimate how the physical state of water adsorbed on cellulose affects various properties, the dielectric properties of moist cellulose were investigated. Three dielectric relaxations were obtained. The relaxation with the lowest frequency was due to electrode polarization. The direct-current conduction calculated from the dielectric loss leaving out the relaxations appearing in mid and high frequencies increased rapidly from 7% or more moisture content (MC). Free water, which can dissolve electrolytes, was increased in the adsorbed water of materials with 7% or more MC. The relaxation appearing in the mid-frequency range was due to interfacial polarization in the heterogeneous structure which consists of adsorbed water with large electrical conductivity within the insulating cellulose. The relaxation appearing at higher frequencies was due to the motion of adsorbed water in cellulose. The relaxation was investigated from relationships between activation enthalpy and entropy in the relaxation. The relationships in low MC cellulose were close to those of sugar, while the relationships in high MC cellulose were close to the relationships extrapolated from bulk water. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnoncrysol.2008.01.003

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In this study, the vapor steaming, by which high moisture condition can be created at elevated temperature up to 170 degrees C, were used to produce wood powder materials (WPM). The effects of production conditions, especially vapor steaming temperature, on the mechanical properties of the WPM were investigated, and feasibility and problems in the production of alternative material for plastics from wood powder without any adhesives were discussed. Results show that the WPM could be produced by lower pressure with vapor steaming as compared with that of a process without steaming since wood components such as lignin and hemicelluloses are remarkably softened by saturated water. The bulk density and the static bending strength of the WPM obtained in the experiment improved linearly when higher temperature vapor steaming up to 150 degrees C was applied with an initial compression of wood powder. However, any increases in the density and strength of the WPM could not be seen at all vapor temperature conditions from 130 to 170 degrees C without an initial compression. This difference in mechanical properties of the WPM for applying an initial compression comes from a degree of degradation of hemicelluloses. For the Charpy impact strength decreases as the vapor temperature was increased regardless of the initial compression conditions. However, a size stability against water obtained from an expansion rate in thickness improved by higher vapor temperature. The maximum static bending strength of the WPM showed about 75 MPa, which is almost same as existing plastics, however the WPM has brittle fracture. The Charpy impact strength was as small as 6.0 kJ/m(2), which should be improved by further works. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2007.08.010

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Plastics depend strongly on underground resources such as petroleum. To produce novel wood materials as a substitute for plastics, the fine structure of wood impregnated with various organic solvents - ethylene glycol(EG), tri-ethylene glycol, dimethyl folmamyde(DMF), dimethyl sulfoxide(DMSO) - was examined. The dynamic Young's modulus and tanδ - frequency curves of every sample indicated that the relaxation process due to the glass transition of lignin in wood exists. To obtain basic data about the processes, the apparent activation energies (ΔE) were examined. The values of ΔE of the sample impregnated with water and EG were higher than that with DMSO and DMF. These results may not only be due to the hydrogen bonding per volume, but also the confined effect in wood. In fact, the CP/MAS spectra of EG - Wood sample indicates the existence of slow movement EG at higher temperatures of the melting point. © 2008 American Institute of Physics.

DOI： 10.1063/1.2988978

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Recently, a plastic-like material has been obtained by compression of wood powder only under an appropriate temperature and pressure conditions. It is considered that this change in a surface texture like transformation comes from auto-condensation of wood components. The static bending strength of the wood powder material (WPM) at 23 degrees C is roughly the same as that of plastics such as ABS, and due to the auto-condensation of wood components the WPM can be enhanced and hardened. These good outcomes mean that the WPM might be applied as a substitute material for plastic without using any petroleum-based adhesives. Such kinds of techniques have become very important for future material. To achieve utilization of the WPM for a plastic application, other properties such as impact characteristics must be investigated. Furthermore, an efficient processing of the WPM using vapor steaming should be developed to reduce processing energy. In this study, a new wood-based product aiming at an alternative material for plastics and its processing with vapor has been researched using wood powder only. Effects of production conditions, namely compression pressure, vapor steaming temperature, heat treatment time and size of wood powder, on the mechanical properties such as bulk density, impact bending strength, bending Young modulus and Charpy impact strength of the WPM were experimentally investigated, and feasibility and problems in the production of alternative material for plastics from wood powder were discussed. Results showed that the impact bending strength and Young modulus were improved with elevated vapor steaming temperature up to about 140 degrees C, and they level off above 150 degrees C. However, the Charpy impact strength only tends to be decreased above 150 degrees C. The impact characteristics of WPM are improved by increasing the compression pressure up to 30 MPa at constant vapor temperature of 160 degrees C. They are hardly changed when the pressure and temperature are applied for more than 5 min of the heat treatment time. The impact characteristics of the WPM have their maximums when the wood powder ranging roughly to 100 mu m in size is compacted under the vapor steaming condition of 160 degrees C. In comparison of the impact characteristics among WPM and engineering plastics, WPM has the maximum Young modulus but has poorest Charpy impact strength. Therefore the Charpy impact strength of the WPM must be improved in our further study. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2007.04.078

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To investigate the possibility and problems in recycling techniques for wood powder compacted material (WPCM) obtained by steam compression, a dynamic mechanical thermal analysis (DMTA) was conducted in dry and wet conditions. The results obtained show that mechanical properties such as the static Young's modulus and bending strength of WPCM increased with an increasing steam temperature up to 170 °C during the compression of the wood powder. It is emphasized that WPCM having a bending strength of 80 MPa with a Young's modulus of 8 GPa can be prepared by steam compressing of wood powder only due to a auto-condensation of wood components. The DMTA showed that the relative storage Young's modulus of WPCM dramatically decreased in water exposure by heating, although it slightly increased in the dry condition. This indicates that WPCM is softened under heat in the presence of water, but it becomes harder by heating without water. The loss tangent peaks showed that the softening behavior of WPCM seems to result from lignin. Consequently, it is thought that WPCM can be shaped by compressing in water, and after obtaining the desired shape, the drying process should be conducted to fix the shape and harden the WPCM. © 2007 Springer Science+Business Media, LLC.

DOI： 10.1007/s10853-007-1723-6

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Language：Japanese   Publisher：The Japan Wood Research Society  

To investigate the fine structure of wood in the non-equilibrium moisture condition, X-ray diffraction (XRD) analysis was conducted during moisture content changes in Japanese red pine specimens. The XRD analysis used a novel measurement system consisting of an X-ray diffraction analyzer with a differential scanning calorimeter (DSC) and a humidifier attached. Moreover, thermogravimetric (TG) measurements were also carried out under the same condition as XRD to estimate the moisture content (MC) during XRD measurement. It was confirmed from TG measurements that MC changed exactly as the humidity changed. However, the value of heat flow of adsorption/desorption of moisture still changed even after MC finished its increase/decrease. Both the (200) peak due to cellulose crystal and the halo peak due to non-crystalline regions shifted to a higher angle with increasing moisture content, and shifted to a lower angle with decreasing MC. Moreover, there was a delay in the (200) peak shift in the desorption process compared with the change of MC. Furthermore, a similar delay in the relative crystallinity change was also observed. These results suggest that the fine structure does not follow RH changes regardless of the agreement between the changes of MC and of RH.

DOI： 10.2488/jwrs.53.82

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The dielectric relaxation due to motions of water molecules adsorbed on wood treated at various temperatures up to 550°C was investigated based on the relationships between activation enthalpy (ΔH) and entropy (ΔS) in relaxation. The relationships indicated two straight lines with different slopes, depending on the treatment temperature. Given the same ΔS, ΔH values for water molecules adsorbed on wood treated at temperatures below 400°C were greater than for those treated above 450°C. It was considered that before heat treatment, water molecules were adsorbed mainly on hydroxyl groups by strong hydrogen bonds and formed ice-like structures. On the other hand, hydroxyl groups were not detected in wood after heat treatments above 400°C. We assume that water molecules are condensed in nanometer-scale micropores that are formed during the carbonization of wood. The relationship between ΔH and ΔS for the motion of water adsorbed on wood treated above 450°C was similar to the value extrapolated from that for bulk water at temperatures below 0°C. We suggest that water molecules are adsorbed on charcoal in a supercooled state. © 2007 by Walter de Gruyter.

DOI： 10.1515/HF.2007.014

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ARBORA PUBLISHERS  

To estimate the physical state of adsorbed water in wood, dielectric properties for wood, paper and charcoal specimens conditioned at various levels of relative humidity were measured in the frequency range from 20 Hz to 10 MHz over the temperature range from 150 degrees C to 20 degrees C. Three relaxations were observed in wood and paper specimens conditioned at high levels of relative humidity. Because the relaxation in the lowest frequency range was affected by the extraction with alcohol-benzene solvent, the relaxation may be due to the electrode polarization. The relaxation in the middle frequency range was also observed in MMA impregnated wood specimen, the magnitude was very large, and the distribution of the relaxation times was very narrow. These facts suggested that the relaxation was assigned to the interfacial polarization in the heterogeneous structure including portions with large electric conductivity of adsorbed water in an insulator of wood. The relaxation in the highest frequency range was ascribed to the motions of adsorbed water molecules. Interestingly, the relaxation was also observed in the charcoal. The theory of rate process was applied to the dielectric relaxation due to the motions of adsorbed water molecules. And the structure of adsorbed water was examined by comparison of the activation energies of the relaxations.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Dielectric properties in three main directions for hinoki wood (Chamaecyparis obtusa) specimens conditioned at various levels of relative humidity were measured in the frequency range from 20 Hz to 10 MHz over the temperature range from -150 degrees C to 20 degrees C. Three relaxations were observed in the specimens conditioned at high levels of relative humidity. The relaxation in the highest frequency range was ascribed to the motions of adsorbed water molecules. The relaxation in the middle frequency range remained unchanged by the ethanol-benzene extraction of specimens. The relaxation location was independent of measuring directions. The relaxation in the lowest frequency range was not detected in the specimens impregnated with methyl methacrylate (MMA). This result suggested that the relaxation was due to electrode polarization. The Cole-Cole circular arc law applied well to two relaxations recognized in the specimens impregnated with MMA. The relaxation magnitude in the middle frequency range was extremely large, and the distribution of relaxation times was very narrow. These characteristics suggested relaxation of the Maxwell-Wagner type resulting from the interfacial polarization in the heterogeneous structure, which included adsorbed water with large electrical conductivity within the insulating cell walls.

DOI： 10.1007/s10086-004-0688-1

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

Delignified hinoki wood and cellulose as well as hinoki and lauan woods were carbonized at 590 degrees C for 1 h. The dielectric properties of these specimens were measured at 20 degrees C in a frequency range of 20 Hz to 1 MHz. Inflection points in the dielectric constant (epsilon') versus the logarithm of frequency (log f) curves as well as in the logarithm of the electric conductivity (log sigma) versus log f curves for all specimens prepared were recognized. Peaks in the dielectric loss and the imaginary part of the complex conductivity versus the log f curves were detected in the frequency location corresponding to the inflection point in the epsilon' and log sigma versus log f curves. It was considered that this relaxation was responsible for the interfacial polarization observed in heterogeneous materials because no permanent dipoles existed in the specimens carbonized above 500 degrees C. The Cole-Cole circular arc law was applied to account for this relaxation. Similar average relaxation times were obtained for all specimens. These results suggested that the observed relaxation was ascribed to interfacial polarization at microscopic levels in the cell walls.

DOI： 10.1007/s10086-005-0705-z

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The dielectric properties of totally dried sugi (Cryptomeria japonica) wood block and powder specimens treated at various temperatures up to 800 degreesC were measured in the range from 20 Hz to 1 MHz and from - 150 to 20 degreesC. Relaxation ascribed to the motion of methylol groups was detected in specimens treated at temperatures below 300 degreesC and its magnitude decreased with increasing temperature. The electric conductivity decreased with increasing temperature up to 400 degreesC. Another form of relaxation was recognized for block specimens treated at temperatures between 500 and 600 degreesC. Cole-Cole's circular arc law was applied to the experimental results. The relaxation magnitude was 60-75 and 24-28 in the longitudinal and radial directions of the block specimens, respectively. Identical relaxation was also observed in the powder specimen. The electric conductivity began to increase remarkably from 500 degreesC. These results suggested that a small volume fraction of particles with large conductivity is formed at microscopic levels in the cell walls. It is considered that this relaxation is due to interfacial polarization. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2003.10.013

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Language：Japanese   Publisher：The Society of Materials Science, Japan  

Changes in the dielectric relaxation of sugi (Cryptomeria japonica) specimens by heat treatment were investigated. Dielectric properties in the longitudinal direction for the oven-dried specimens were measured in the range from 20Hz to 1MHz and from -150&deg;C to 20&deg;C. The relaxation due to the orientation of methylol groups was observed for the specimens treated at the temperature up to 300&deg;C. The relaxation magnitude obtained from the Cole-Cole plots did not change by the heat treatment up to 200&deg;C, but it decreased remarkably above 200&deg;C and became 0 at 300&deg;C, showing the disappearance of methylol groups. Any relaxation was not detected within the range measured for the specimens treated at the temperature between 300&deg;C and 450&deg;C. However, one relaxation was recognized for the specimens treated at the temperature between 500&deg;C and 600&deg;C. Regarding the specimen treated at 500&deg;C as a system in which a small amount of ellipsoids of graphite disperses in the medium of an insulator, the applicability of the Maxwell-Wagner's theory to the tan&delta; versus logarithmic frequency curve at 20&deg;C was examined. A good agreement between the experimental and calculated results was obtained in the case that long and narrow ellipsoids oriente to the direction of the electrical field. These results suggested that the relaxation was due to the interfacial polarization.

DOI： 10.2472/jsms.52.362

CiNii Books

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Language：English   Publisher：Wood Research Institute, Kyoto University  

CiNii Books

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Language：Japanese  

DOI： 10.1299/jmmp.3.624

CiNii Books

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Applicant：奈良県, 国立研究開発法人産業技術総合研究所

Application no：特願2010-028501  Date applied：2010.2

Announcement no：特開2011-161835  Date announced：2011.8

Patent/Registration no：特許第5864078号  Date issued：2016.1

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Applicant：独立行政法人産業技術総合研究所

Application no：特願2009-178319  Date applied：2009.7

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Patent/Registration no：特許第5500541号  Date issued：2014.3

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Applicant：奈良県, 株式会社ヨコタニ, 国立研究開発法人産業技術総合研究所

Application no：特願2009-005578  Date applied：2009.1

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Applicant：独立行政法人産業技術総合研究所

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Applicant：独立行政法人産業技術総合研究所

Application no：特願2008-335354  Date applied：2008.12

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Patent/Registration no：特許第5327791号  Date issued：2013.8

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Applicant：独立行政法人産業技術総合研究所

Application no：特願2008-204631  Date applied：2008.8

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Applicant：独立行政法人産業技術総合研究所, 清水建設株式会社

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Applicant：独立行政法人産業技術総合研究所

Application no：特願2006-213305  Date applied：2006.8

Announcement no：特開2008-036941  Date announced：2008.2

Patent/Registration no：特許第4849609号  Date issued：2011.10

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