This paper highlights a number of articles on research and development on wood composites. The coefficient of variation in the mechanical properties of wood components tends to decrease when the thickness of the wood elements decreases. This finding was utilized in the manufacture of hollow cylindrical columns of laminated veneer lumber (LVL) from Cryptomeria plantation thinnings. In the future, the marketing of wood composite boards will tend toward two types: thick boards with low density properties and thin boards with fiber orientation. For the production of thick boards, fundamental parameters and application of steam-injection pressing have been studied, and continuous steam-injection pressing has been developed. For thin board production, generation principles of aligning torque in high-voltage system and the application has been studied. A new oriented mat former with electrodes positioned only at the reverse side of a forming belt has been developed. Various synthetic resins of low-molecular weight have been applied to improve dimensional stability of laminated products, such as LVLs and particleboards. Acetylation and formalyzation of fibers and particles were investigated to provide stabilized panels. High pressure steam treatment during pressing of wood composites has been studied and the process has been found effective and promising.
Introfluction
The use of glued-laminated wood has lately increased remarkably in Japan in heavy timber constructions with revision of building regulations. For the sake of future wood resources in Japan, however, there is a need for development of structural wood composites that could be made from lower-grade resources such as thinnings, industrial residues and others, aside from those used for glue-lam.
For structural panels in Japan, wood composition boards can be substituted for plywood. As a substitute, it is predicted that attention will be focused on the development of production technology for boards with a high moment of inertia (thick boards) or oriented or other functional boards manufactured from smaller strands (semi strand) than those used for ordinary oriented strand board (OSB) in North America. Physical and chemical processing will also be useful in improving board properties to meet structural requirements.