We evaluated the water and gas adsorption performances of sugi (Cryptomeria japonica D. Don) crosscut and quarter-sawn specimens, which were given three or six repetitions of dry-and-wet treatments under the room temperature or high temperature conditions. Equilibrium moisture content of all specimens decreased with the progress of repeated wet-and-dry treatments, regardless of the effect of heating. On the other hand, amounts of nitrogen gas adsorption increased with the progress of repeated wet-and-dry treatments, especially in the quarter-sawn specimen. These phenomena, observed in both water and nitrogen gas adsorption, suggest that repeated drying and re-swelling decreased the amount of hydrophilic regions such as noncrystalline cellulose at the microscopic level. It is also considered that cracks and pores would arise on the surface of wood cell walls at the submicroscopic level.

View full abstract

Surface colors are very important properties of timbers. However, there were few studies which examined relations between drying conditions and the surface colors of timber. In the present study, the surface colors of sugi timbers (Cryptomeria japonica) dried by five different conditions (air drying, medium temperature drying, vacuum drying, high frequency drying, and high temperature drying) were measured using an imaging spectrometer. This device was a spectroscopic colorimeter based on imaging technology, and the surface colors of the four parts of each specimen (sapwood-earlywood, sapwood-latewood, heartwood-earlywood and heartwood-latewood) were measured separately. This minute color measurement revealed the following results: 1. Kiln dried sugi specimens became darker than the air dried specimens, especially in the sapwood-earlywood part. 2. Reddish colors in the heartwood-ealrywood part were selectively reduced by the drying process which includes the high temperature setting. 3. The surface colors became monotonous because the sapwood became darker and more yellowish, and the contrast between sapwood and heartwood was reduced.

View full abstract

Warm color of wood is a very important design factor for building materials, furniture, and so on. Therefore, color measurements for the surfaces of timber and wood products are often performed using a colorimeter. However, most of such color data are mean values inside a confined measurement area, and these values are entirely compared and evaluated based on L^*, a^*, b^* and ΔE^* values. In the present study, surface colors of sugi timbers (Cryptomeria japonica) dried by five different conditions were measured using an imaging spectrometer, and surface colors of 4 parts (heartwood-latewood, heartwood-earlywood, sapwood-latewood, and sapwood-earlywood) were examined for each drying condition based on the three color attributes (lightness L^*, chroma C^*, and hue angle H °). The color analysis revealed very clear linear relations between H ° and L^* regardless of drying conditions. Although the surface colors of the 4 parts were clearly distinguished from each other in the air-drying condition, the range of hue angle became narrow as the drying conditions became more severe and it was difficult to distinguish the two parts of heartwood-earlywood and sapwood-latewood by their colors. Originally bright surfaces such as the sapwood-earlywood part selectively darkened (lower lightness) and deepened (higher chroma) by the kiln drying.

View full abstract

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate the distribution of inorganic elements and a heartwood compound, hinokinin, in discolored ancient woods of hinoki cypress derived from Sanjusangen-do and Horyuji Temple. The tendency of the distribution of hinokinin in the heartwood was similar for the ancient woods and a wood sample freeze-preserved immediately after cutting. In contrast, the distributions of the inorganic ions in the ancient woods were inconsistent with those of the freeze-preserved wood, as the concentrations of the inorganic ions, Na, K, and Ca were higher in the sapwood than in the heartwood of the ancient woods. The result suggests that the concentrations of the inorganic elements in the heartwood and sapwood were altered during the long-term drying process in the ancient woods. The TOF-SIMS analysis also showed that detecting the distribution of the inorganic ions is useful to distinguish the sapwood from heartwood in dendrochronological dating of ancient woods.

View full abstract

To improve the durability of a particleboard subjected to outdoor exposure, the surfaces of the board were coated with a polyurethane resin. After five-year exposure, the retentions of modulus of rupture and internal bond strength for the uncoated board were 70.6% and 67.6%, respectively, whereas those for the coated board were 91.3% and 85.0%, respectively, showing that coating of surfaces improves its modulus of rupture and internal bond strength. The surface of an uncoated board is vulnerable to damage by rainwater and sunshine; further, rainwater can easily penetrate into board's interior. However, it is difficult for rainwater to penetrate into the interior of a coated board, which makes such a surface well protected from damage. Therefore, coating increases the durability of the board.

View full abstract

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a powerful tool to reveal the chemical distribution in many materials. We have applied TOF-SIMS to investigate the distribution of organic biomolecules and inorganic metals in plants. The positional, temporal, and quantitative information of water-soluble chemicals in a living state are essential information to elucidate many biological mechanisms. However, traditional quantification of water-soluble chemicals such as coniferin and sucrose depends on a bulk-analysis providing an approximate position of them. To analyze the position and quantity of the water-soluble chemicals in more detail, we developed the cryo-TOF-SIMS/SEM system. The system consists of a glove box, a cryo-SEM, and a cryo-TOF-SIMS, which were interconnected by a cryo-vacuum shuttle. By using the system, successive TOF-SIMS measurements and SEM observations are possible for the frozen-hydrated samples. We applied the system to freeze-fixed Ginkgo biloba and estimated the distribution of water-soluble chemicals: coniferin and sucrose. The quantity of coniferin and sucrose were evaluated by HPLC and ion chromatography, respectively. As a result of cryo-TOF-SIMS/SEM analysis, the secondary ion derived from coniferin and sucrose was unevenly distributed in phloem, tracheids, or ray cells.

View full abstract

In the present study, we modified micro-fibrillated cellulose (MFC) mechano-chemically by a surface treatment with calcium silicate hydrate, in order to develop an effective filler material for producing wood-plastic composites (WPC). The surface modification could be performed efficiently by the combination of a wet ball-milling process in the presence of silica powder and Ca(OH)₂ and a subsequent hydrothermal treatment, giving rise to a formation of tobermorite crystals of calcium silicate hydrate. The surface-treated MFC products exhibited high heat resistance and no irreversible aggregation even after normal heat-drying at 60°C. By an addition of the modified MFC filler to polypropylene-based WPC, the composite materials demonstrated high mechanical strength and high elastic modulus.

View full abstract

This paper deals with testing the stress distributions and strength in single-lap adhesive joints of bamboo plate adherends after being subjected to static bending moments. Stress and strain were calculated using an elastic and orthotropic finite-element method (FEM). In addition, the surface strain distributions of single-lap adhesive joints under static bending moments were measured using strain gauges. Reasonable correlation was found between the numerical and the experimental results. It was found that the maximum value of the maximum principal stress, σ₁, appears at the interface between the adhesive layer and the adherend. The normal stress in the direction perpendicular to the fiber was greatest near the singular points. Bending strength tests were performed. In the case where the width of the joints and the lapped length were equal, it was found that the bending strength was maximal. Furthermore, the joint strength was predicted using two singularity parameters from the calculation results. Fairly good agreement was found between the predictions and the experimental results.

View full abstract

Properties of deodorizing filters for tobacco gas with activated carbon made from pruned apple branches on H₂O-activation with loaded reagent was investigated by comparison with the commercial activated carbon from coconut shells. The results are as follows. Both external specific surface area and mesopore volume were larger in the experimental than in the commercial activated carbon. Besides it was not found that in the range where it was limited, the distribution of micropores and mesopores was lower. Activated carbon from pruned apple branches showed a faster removal time of tobacco gas from an early period of use in a fixed period of time. This was assumed to be caused by the large external specific surface area and mesopore volume.

View full abstract