In the wood industry, large quantities of wastes are generated. Bark is one of the typical wastes, and the rate of its utilization is considerably lower than that of other main wood wastes such as slabs and sawdust. Recently, it has become an important matter to develop an effective utilization of woody biomass ; however, the present use of bark is restricted to compost and livestock bedding, etc. Therefore, development of high-valued utilization of bark is greatly anticipated. Condensed tannins are present at very high concentrations in the bark of tree species, and many investigations of their new utilization have been reported. Furthermore, several modifications of condensed tannins have also been studied to improve their function or to develop their efficient utilization. This paper reviews progress made in the fields of chemical characteristics of condensed tannins and their chemical- and enzymatic-conversions, and finally describes prospects of bark tannin utilization.

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Racking tests of floor diaphragms with 30 mm thick particleboard, and the JIS 13 type, were conducted to confirm this board's feasibility as a sheathing material. Racking resistance of the diaphragms was also numerically analyzed. As a result, racking resistance of floor diaphragms with the particleboard sheathed with screws seemed to be stronger than that of floor diaphragms with the particleboard sheathed with nails, but the ductility of floor diaphragms sheathed with screws was less than that of floor diaphragms sheathed with nails. Also, the racking resistance of floor diaphragms with narrow particleboard was lower than that of floor diaphragms with standard size particleboard. Estimated load-shear strain curves of floor diaphragms analyzed with numerical calculation agreed with the observed curves of floor diaphragms sheathed with nails until ultimate deformation, by using load-slip curves of timber joints with nails or screws and the observed shear stiffness of the particleboard. On the other hand, estimated curves of floor diaphragms sheathed with screws somewhat differed from the observed curves after maximum load. This disagreement seemed to depend on the differences in failure modes between the single shear joint tests and racking tests.

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A three-dimensional molding method has been developed to make wood an alternative resource of plastics. This method is an unprecedented way of wood processing which uses deep-draw wood molding. To establish this method, development of stretchable and flexible semi-fixed compressed wood which provides optimum properties for three-dimensional molding by deep drawing, and clarification of its best fabricating steaming conditions are necessary. In this study, semi-fixed compressed woods were fabricated from Cryptomeria japonica and Chamaecyparis obtusa under various temperature and time conditions, and their mechanical properties were examined. The results indicated that the best steaming conditions for Cryptomeria japonica were 2-hour preliminary softening at 110°C, followed by 1-hour softening at 150°C which provided 97.8% elongation. For Chamaecyparis obtusa, it was 2-hour preliminary softening at 110°C, followed by 1-hour softening at 140°C which provided 107.4% elongation.

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To improve the heat resistance of an aqueous vinyl polymer solution-isocyanate adhesive (API), we examined the film properties and the wood bonding performance of polyvinyl alcohol (PVA), which is generally used as a base polymer for API, with addition of montmorillonite, a form of clay. We measured the viscosity of the PVA solution with addition of montmorillonite in terms of the time required for mixing, the dynamic viscoelasticity, and the X-ray diffraction of a film made from the PVA solution with addition of montmorillonite. The viscosity of the PVA/montmorillonite solution increased with increasing mixing time. X-ray diffraction analysis showed that the layer of montmorillonite expanded after mixing with PVA. These properties demonstrated that the interaction between PVA and montmorillonite increased after mixing the two compounds. The storage modulus at high temperatures of the PVA/montmorillonite mixture was ten times that of PVA alone. In wood bonding, the bond strength of the PVA/montmorillonite mixture increased at high temperatures. These results show that adding montmorillonite to PVA increases the heat resistance of the adhesive.

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A butt-rot disease of sugi (Cryptmeria japonica D. Don) wood has recently increased in reforested areas, but its damage level seems to depend on the clone variety. Aya sugi is susceptible to the butt-rot disease, but, Yabukuguri sugi, Measa sugi, and Yanase sugi are relatively resistant to it. The latter three showed relatively higher contents of methanol extractives and quite different constitution of norlignan compared to the former. Main norlignans from the latter three are agatharesinol and sequirin-C whose contents are thought to be crucial for the resistance against butt-rot disease of sugi wood. Antifungal tests of the extractives against the wood-rot fungi isolated from sugi butt-rot woods confirmed the importance of the methanol extractives and these norlignans.

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Short term effects of wooden or vinyl interiors finishes on reducing fatigue/stress after acute psychological stress using Uchida-Kraepelin Test (UKT) were studied. Profile of Mood States (POMS) as psychological parameters and Chromogranin A (CgA), Cortisol and Immunoglobulin A (IgA) in saliva as biochemical parameters, were examined in twenty healthy subjects comprising university students and white collar workers. Average score of negative mood items of POMS, Tension-Anxiety (T-A), Depression-Dejection (D-D), Anger-Hostility (A-H), Fatigue, Confusion, all decreased (p < 0.01) after 30 minutes in wooden finishing interior , on the other hand, there was no significant change found in vinyl finishing interior. Changing pattern of average value of CgA, Cortisol, and IgA at several points in the experimental period suggested that the sympathetic nerve system got excited just after UKT and tended to subside gradually in both interiors, but there was no difference found between wooden and vinyl interior finishes. Further investigations are required using more effective means of inducing acute psychological stress on the subjects, and a larger number of subjects.

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