The Dielectric Properties of Wood IV : On Dielectric Dispersions of Oven-dried Wood

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。In this paper, the dielectric absorptions of oven-dried wood were investigated. There existed three dielectric absorptions in wood. The position of dielectric absorption in high frequency range at low temperature coincided with that of viscoelastic one, and the relaxation process may be associated with the motion of CH_2OH groups in the disordered region of wood substances. The absorption of oven-dried KUSUNOKI appeared in low frequency range at room temperature may be due to the existence of the conductive material and was influenced by the shape of the material in wood. The absorption in very low frequency range at high temperature may be associated with the segmental motion of molecules in the amorphous region accompanied by thermal degradation

<Note>Some Physical Properties of Wood and Cellulose Irradiated with Gamma Rays

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。The effect of gamma irradiation from cobalt-60 on specific gravity, degree of crystallinity, thermal softening temperature, tensile strength and torsional creep behavior of wood and cellulose were investigated and the following results were obtained. 1) A dosage up to about 10^8 rad had little effect on the specific gravity of wood and cellulose. 2) The degree of crystallinity of wood and cellulose remained almost unchanged up to 3×10^7 rad, but started to decrease rapidly at about 1×10^8 rad. 3) The softening temperature of cellulose shifted gradually to a lower temperature region up to about 3×10^7 rad and abruptly in the range exceeding 3×10^7 rad. 4) Strength of wood decreased with increasing irradiation dosage, depending remarkably on loading modes. 5) The value of creep compliance of wood at time 0.1 min did not change up to 1×10^7 rad, but increased markedly in the range exceeding about 3×10^7 rad

<Preliminary>Thermal Softening of Wet Wood in the Temperature Range of 0 to 200℃

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました

<Preliminary>The Influence of the Temperature Change Rate on the Humidity Control Effect of Wood

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました

Stabilization of Acoustical Properties of Wooden Musical Instruments By Acetylation

Because variable humidity affects the acoustic properties of wood, manufacturers of wood instruments must minimize dimensional changes caused by the absorption of water. Acetylation reduces the moisture content of the cell wall, thereby increasing the stability of the acoustic and dimensional properties of wood under conditions of changing humidity. The acetylation of wood slightly reduces sound velocity (by about 5%) and also reduces sound absorption when compared to unreacted wood. Hence, acetylation does not change the acoustic converting efficiency

Effect of Humidity on Vibrational Properties of Chemically Modified Wood

Changes in vibrational properties of wood can be used to determine changes in the wood cell wall resulting from chemical modification. The dynamic Young's modulus to specific gravity ratio (E'/γ) and internal friction (tan δ) for chemically modified wood compared to those for untreated wood showed major differences in cell-wall modification and lumen filling modification. Increasing the moisture content of the cell wall also has a major effect on the vibrational properties of chemically modified wood. In general, treatments that resulted in lowering the moisture content of the cell wall also lowered internal friction within the cell wall. Vapor phase reactions with formaldehyde had the greatest effect in stabilizing the cell wall against changes in dynamic mechanical properties with increasing moisture content

Dimensional Stability, Decay Resistance, and Mechanical Properties of Veneer-Faced Low-Density Particleboards Made From Acetylated Wood

Veneer-faced low-density particleboards were made using four combinations of control and acetylated veneers and particles. These boards were tested for dimensional stability in both liquid water and water vapor, for decay resistance in standard soil-block tests with Tyromyces palustris and Trametes versicolor, for strength losses during attack by T. palustris, and for mechanical strength in bending-creep and mechanical tests. Boards made from acetylated veneers and acetylated core particles showed excellent dimensional stability in both liquid water and humidity tests and were resistant to attack by both fungi in an 8-week soil-block test. During the 150-day bending-creep test, the totally acetylated boards showed no strength or weight loss during exposure to T. palustris. Modulus of elasticity and modulus of rupture were slightly reduced for totally acetylated boards compared to boards with control veneers and control particles, and internal bond strength was reduced by about 30%. Screw-holding capacity of the totally acetylated boards and boards with control veneers and particles was essentially the same

Fixation of Compressed Wood Using Melamine-Formaldehyde Resin

Methods to maximize wood hardness and dimensional stability include various combinations of compression, heating, and chemical treatment. In this study, wood was treated with increasing concentrations of a low molecular weight, water-soluble melamine-formaldehyde resin solution (mol wt 380) and compressed while heated. This method achieved a maximum bulking efficiency of 5% and an antishrink efficiency of 45%, showing that the chemical had not completely penetrated the cell wall. Once the wood was treated, its ability to retain the compressed state was tested by immersing wood specimens in water at different temperatures. Specimens treated with an 8% resin solution retained almost complete fixation when soaked in room-temperature water, while those treated with a 25% solution retained fixation in boiling water. Moreover, a 25% solution of resin and a compression of 54% increased hardness from 0.48 to 0.72 MPa

Dielectric Properties of Wood

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<Original>Three Dimensional Analysis of Elastic Constants of the Wood Cell Wall

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。The elastic constants of wood cell wall were theoretically analyzed using two cell wall unit models and three sets of elastic constants for lignin-hemicellulose matrix. The Young's modulus of the cell wall layers in the direction perpendicular to the microfibril orientation increased remarkably with increasing Young's modulus and shear modulus of the matrix, although that in the microfibril direction didn't change significantly. The Young's modulus and shear modulus of the cell wall layers differed between the models depending on the volume fraction of cellulose and the presence of non-crystalline cellulose. The decrease in the longitudinal Young's modulus of the cell wall with the S_2 microfibril angle became more gentle with increasing Young's modulus and shear modulus of the matrix. A comparison between calculated and experimental results indicated that the wood cell wall would contain a non-crystalline cellulose with lower elastic moduli than crystalline cellulose and the Young's modulus of the lignin-hemicellulose matrix is at least more than 2 GPa