In 1926-1936, H. Staudinger clarified scientifically the existence of “macromolecules” in which low molecular substances link together by covalent bonds. In the experiments for this clarification, he used the solutions of cellulose and its derivatives. At the present time, it seems that many researchers in the field of cellulose science are interested in the structure and properties of the solid (crystalline) state of cellulose. However the investigations for the solution properties are also very important for characterizing cellulose as a “macromolecule”. This review provides an insight into the molecular characteristics of cellulose through its solution properties using light scattering and rheological methods.

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The lateral impact vibration method is a non-destructive and high through-put method to estimate heartwood moisture content (MC) in living trees. We applied this method to an investigation of 37 clones of Cryptomeria japonica (in total over 1000 trees) in a clonal test stand. With two measurements in 2000 and 2001, the repeatability of this method was very high for the fundamental frequency (f) of vibration of the stem resonated by lateral impact. The value of 1/f could be shown to be a function of stem diameter (d). The regression lines differed between clones, and the relationship between d and 1/f characterized each clone. Fifteen clones (in total 103 trees) from this test stand were harvested and the MC of the trees was measured. Although 1/df could predict MC, the precision of the prediction was not good enough. However, the rank of the clonal means of 1/df was almost identical to the rank of the clonal means of MC. It is concluded that the lateral impact vibration method is suitable for the ranking of clones, and therefore for selecting clones, and that this method is applicable and useful for genetic improvement of MC in C. japonica.

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In contrast to exterior materials, house interior materials are not directly exposed to rain and only receive the sunlight that penetrates through window glass. Recently, various kinds of double-glass panes have often been used for windows in Japanese houses in place of a conventional single-plate glass. Wavelength and irradiance of transmitted light vary greatly according to the kind of window glasses. Therefore, to establish a method of evaluating the photo-stability properties of interior materials, we designed a new accelerating-test apparatus with a metal halide lamp as the light source and a pane of glass between the lamp and the samples. Both the spectrum of transmitted sunlight through glasses and that of transmitted light in this apparatus were measured.
With respect to the spectrum of transmitted sunlight through glasses, the irradiance decreased especially in the low wavelength of the ultraviolet range, in the order of single glass, double glass, low emissivity double glass, solar reflection double glass, and laminated solar reflection double glass. On the other hand, the spectrum of transmitted light in this apparatus showed similar changes, especially in the ultraviolet range. These results prove that the apparatus is effective in the evaluation of the photo-stability properties of house interior materials.

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This research is a continuation of part 1¹⁾, and focuses on studying the effect of cyclic humidity changes. It also evaluates the anti-relaxation effect by deformation recovery of the komisen(wooden square key) made of sugi(Japanese ceder ;Cryptomeria japonica D. Don) compressed wood on the contact stress within the hozo-komisen joint (traditional wooden mortise and tenon joint stiffened by the inserted wooden square key) in the Japanese traditional post and beam structures.
The summery of this paper is as follows.
The contact force on small load cells in joints with compressed sugi komisen inserted is shown to higher(40N) than that of joints made of shirakashi (Quercus myrsinaefolia Blume) at 80% relative humidity(RH), and reaches 56N at RH 85%.
The contact force on small load cells in joints with compressed sugi komisen inserted increased from 20N to 27N, but in joints with shirakashi komisen inserted it decreased from 14N to 13N at RH40% of the complete cycle. It is concluded that compressed sugi komisen has the effect of preventing relaxation of the contact stress between joint parts by cyclic changes of relative humidity.
As to change of maximum swelling stress(σ_max) due to the cyclic changes of relative humidity at 40%-80% in the restraint condition, in shirakashi it decreased to 3.3 MPa at the 3 rd cycle, but compressed sugi attained 4.6 MPa at all cycles. This clarified the reason why compressed sugi komisen has a higher anti-relaxation effect than shirakashi komisen.

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Lagscrewbolts were developed as simple and economical moment-resisting connectors for glulam constructions. A lagscrewbolt has two threads :a screw type thread on the outside surface at one end and a bolt type thread at the other end of the shank. A lagscrewbolt is embedded into a glulam member by the screw thread and connected to another piece by the bolt thread. The theory on pull-out resistance of an embedded lagscrewbolt parallel to the grain direction was developed in a previous paper. The purpose of this study was the development of a theory on pull-out resistance perpendicular to the grain direction and its verification using experimental results. The theory for perpendicular to the grain was developed on the basis of Volkersen theory, similar to the theory of parallel to the grain. Shear strength perpendicular to the grain direction fv₉₀ and shear stiffness Γ₉₀, both necessary parameters in the theoretical formula, were determined by pull-out tests of thin 15-mm specimens made of glulam. The effective area of glulam (A_w) was determined by an energy equivalent concept, the deformation energy by the theory of a beam on an elastic foundation or the bending theory of a short beam as being equal to the deformation energy of work at the effective area of the glulam. A verification experiment was conducted by using three kinds of lagscrewbolts, in which the top threat diameters were 25, 30 and 35mm, and influences of various embedment depths on the pull-out properties were examined. The developed theory predicted maximum pull-out load and slip modulus well.

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In order to prepare wood specimens for subsequent measurements of mechanical properties, we examined the selective and uniform elimination of wood constituents from a 4 mm thick cross section of hinoki (Chamaecyparis obtusa Endl.). The results are summarize as follows:
1) Lignin was uniformly eliminated by a modified Klaudiz's method (45°C, ∼72h) throughout the block. Moreover, the amount of remaining lignin could be controlled by varying the reaction duration. The uniformity was confirmed also by a consideration of reaction kinetics.
2) The elimination of hemicellulose was carried out in an 0.4% aqueous solution of NaOH under high temperature and pressure. These conditions promoted the instantaneous and uniform diffusion of the reagent into the interior of the wood block. As a consequence hemicellulose was easily eliminated even from the thick cross section. The amount of remaining hemicellulose could be controlled by varying the concentration of NaOH.
The method proposed here assures the uniformity of wood constituents throughout the wood block, and would be widely applicable to purposes other than the mechanical tests, although the lack of ununiformity between inner and outer layers of cell wall may remain.

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We developed a continuous press machine to manufacture compressed laminated veneer lumber(c-LVL) using a high frequency (HF) heating method. The materials were compressed between metal plates followed by HF heating and were then conveyed to the cooling process via bearing rollers attached to the metal plates. As a result, the separation between the heating and cooling processes improved production efficiency.
The 6-ply c-LVL was manufactured from Sugi (Criptomeria japonica D. Don) sapwood, 2000mm (L)x12mm (R)x75mm (T) under 50% compression. Following the heating and cooling, the c-LVL shows little set recovery except for the area at the longitudinal ends. We found that a suitable adhesive for HF heating method was a water-based vinyl polymer-isocyanate resin. The increase in number of pieces of laminated veneer enhanced the dimensional stability of the c-LVL, restrained warping after pressing, and had no effect on the bending strength.

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