Wood and Fiber Science (E-Journal)
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Modeling Wood Moisture Sorption Hysteresis Based on Similarity Hypothesis. Part 1. Direct Approach
Get PDFA similarity-hypothesis approach to modeling sorption hysteresis in porous media has been applied to wood. The method, which uses the adsorption and desorption relative humidities directly as similarity statement parameters, is simpler than previously reported techniques based on the independent-domains theory since only the boundary curves of the main hysteresis loop are required in order to generate the scanning curves at a given temperature. A comparison of the predicted scanning curves with actual experimental data for yellow-poplar (Liriodendron tulipifera) indicates that the approach is highly reliable, with predicted values within 0.01 to 1.05 of the actual equilibrium moisture content of the samples at different relative humidity levels
A Multivariate Model of Power In The Relationship Among Suppliers And Resellers of U.S. Forest Products Entering Selected Markets of The European Union
Get PDFIssues relating to power in marketing decision-making in forests products trade are seldom analyzed and are poorly understood. Consequently, no reliable analytical models are in place. This paper presents the results of a univariate and a multivariate statistical analysis that describes power in the relationship between different types of intermediaries for three countries in the European Union (EU). Understanding this dimension of the channel relationship will assist forest products firms in developing effective policies for dealing with intermediaries in the EU.To analyze power, a survey instrument identified eleven areas of responsibility/power among suppliers and resellers of U.S. hardwood, softwood, and softwood plywood in the United Kingdom, Germany, and the Netherlands. The results clearly illustrated that resellers from the EU countries perceived that they hold more responsibility/power than their U.S. suppliers over the majority of marketing decisions. In general, the results of a univariate analysis found that on a broad level there were major differences between resellers that took title versus resellers that did not take title. The largest differences between these two groups were among the variables associated with distribution and pricing.The results of a multivariate analysis indicated that power among resellers can be summarized by two factors termed "Strategic Planning Responsibility" and "Service Responsibility." The analysis indicated that the difference in perceived power between resellers that take title versus those who do not take title is in the strategic planning dimension, where emphasis is on pricing and distribution responsibility
Selected Mechanical Properties of Fast-Growing Poplar Hybrid Clones
Get PDFTwenty-eight nine-year-old trees from ten clones of the hybrid Populus x euramericana from one site in Quebec were sampled to study the variation of selected mechanical properties within trees, within clones, and among clones. Four small and clear ASTM wood samples were taken from each tree at breast height, as well as a 10-mm diameter increment core. The parallel-to-grain compliance coefficient and ultimate crushing strength were evaluated on the ASTM samples for air-dry and green conditions. The dynamic compliance coefficient was measured on increment cores using an ultrasonic wave propagation method. Differences in all mechanical properties among clones were highly significant, while variation among trees was generally not significant. The dynamic compliance coefficient tended to be lowest near the pith, increased to a maximum at one third of the tree diameter, and then decreased outward towards the bark. There was also a highly significant correlation between mechanical properties of ASTM samples and dynamic compliance coefficients of increment cores. Mechanical properties were only moderately correlated to wood density. Finally, there was a significant but weak correlation showing that wood density and mechanical properties decreased with increasing growth rate
Chemithermomechanical Pulping Characteristics Of Budworm-Killed Trees
No full textChemithermomechanical pulps (CTMP) were produced from balsam-fir trees [Abies balsamea (L.) Mill] that were harvested one and three years after they were killed by spruce budworm beetles. Laboratory tests revealed that the spruce budworm produced significant reductions in wood density (30%), fiber length (19%), long fiber fraction (36%), brightness (4%), tensile strength (25%), and burst strength (24%), but most significantly in the tear strength of paper (51%). However, these negative effects were accompanied by some positive results, e.g., a 15% decrease in the energy of refining, a 73% reduction in pulp rejects, coupled with a 108% increase in the fine content of the pulp and by a 5% increase in the opacity of paper. In order to profit from the above advantages and to prevent any further reduction in the quality of paper, the dead trees must be harvested within three years of their defoliation—the sooner, the better
Testing Small Wood Specimens In Transverse Compression
Get PDFThe standard test method recommended in ASTM Standard D143 for compression perpendicular to the grain does not measure pure compression. The results of small wood specimens tested in compression perpendicular to the grain may be influenced by macroscopic characteristics of the specimen or the test procedure. Pure compression tests were performed on wood and poly(methyl methacrylate) specimens measuring 0.12 to 1.56 inch in height. Young's modulus in transverse compression increased with specimen height. Yield stress was not affected by specimen height. However, an increase of specimen height resulted in a decrease of yield strain. These observations may be explained by surface roughness or non-parallelism of the specimen. The results are not unique to wood
Investigation of Poly(4-Vinylphenol) As a Wood Adhesive
Get PDFAn increasing concern about the effect of emissive VOC (volatile organic compounds), especially formaldehyde, on human health has prompted a need for more environmentally friendly adhesives. Mussels stick to rock or other substances very strongly in seawater through secreting phenolic protein adhesives, termed marine adhesives. The marine adhesives are formaldehyde-free and environmentally friendly. However, the marine adhesives are not readily available. In this study, we investigated whether a polymer, poly(4-vinylphenol) (PVP), containing phenolic hydroxyl groups, but no peptide linkages, could be used as a wood adhesive. The shear strength of wood composites bonded with an aqueous suspension of PVP could reach up to 3 MPa. Addition of 1,6-hexanediamine or diethylene-triamine to the aqueous suspension of PVP resulted in a significant increase of the shear strength. When the molar ratio of the phenolic hydroxyl group in PVP vs. 1,6-hexanediamine was 3:1, the shear strength could be twice as high as when the aqueous suspension alone is used. Curing mechanisms of PVP and 1,6-hexanediamine/diethylenetriamine are believed to be the same as those found in the naturally occurring quinone-tanning process. The adhesion mechanisms by which marine adhesives bond mussels to rock could be applied to development of a formaldehyde-free wood adhesive system
Moisture Content Effect on Tensile Properties of Individual Douglas-Fir Latewood Tracheids
No full textA testing system was developed to determine tensile properties of single wood fibers under precisely controlled relative humidity conditions. Individual delignified Douglas-fir summer-wood tracheids were tested axially in tension at moisture contents of 0, 6, 12, 18% and in a water-soaked condition. Load-elongation curves were predominantly linear to failure and curve shape was unaffected by moisture content, implying that stresses in tracheids were borne primarily by a structural framework with a high degree of crystallinity. Moisture content significantly affected tracheid tensile properties. Tracheids tested wet exhibited the lowest strength and elasticity. The overall relationship between strength properties and moisture was curvilinear with maxima in tensile strength and modulus of elasticity at about 12 and 6% moisture content, respectively. Tensile strengths obtained were higher than published values for other cellulosic fibers. Maximum internal stresses on the cellulosic framework of tracheids were considered to approach those theoretically calculated for cellulose chain seission, suggesting highly crystalline microfibrils containing an extended-chain crystal lattice structure
Three-Dimensional Analysis of Elastic Behavior of Wood Fiber1
No full textAn exact solution of stress for each layer of cell wall under tension has been obtained by considering wood fiber as a hollow composite anisotropic circular cylinder. Numerical results of stresses and the relative angle of twist of a single fiber, as well as the values of each layer of the cell wall, are given for six hypothetical wood fibers
Prediction of Bow and Crook in Timber Studs Based on Variation in Longitudinal Shrinkage
Get PDFThis paper presents a model that describes the change in magnitude of bow and crook between two moisture contents below the fiber saturation point. The model shows that the variation in the longitudinal shrinkage coefficient over the cross section and along the stud could explain most of the change in bow and crook in the studs. It was possible to identify evenly curved bow and crook, as well as S-shaped bow and crook. The results show that the model predicts changes in bow better than changes in crook.The results of measurements of distorted geometry along the length of 12 studs are presented. The equipment for measuring distorted geometry is described. The distorted geometry was measured at two moisture contents. The studs were then sawn into sticks (10 X 10 X 200 mm), a total of 3,600. The longitudinal shrinkage coefficient in these sticks was obtained for a change in moisture content from 18% to 8%. The sticks were also classified visually into three groups depending on their compression wood content: no compression wood, mild compression wood, mild compression wood, or severe compression wood.The variation in the longitudinal shrinkage coefficient was large in the studied sticks (x 0.0111, SD 0.0111). The sticks classified as containing severe compression wood had a significantly larger longitudinal shrinkage coefficient than the sticks classified as no or mild compression wood. Moreover, sticks classified as mild compression wood had a significantly larger shrinkage coefficient than the sticks classified as no compression wood
Classification of Wood Surface Features by Spectral Reflectance
Get PDFA database of spectral-reflectance curves of Douglas-fir veneer surface features is presented and analyzed via principal-component analysis. The paper describes how such analysis can be used to model and classify the spectral-reflectance curves by feature type. For modeling (curve-reconstruction) purposes, three principal components were sufficient by most criteria. For classification purposes, seven principal components achieved classification accuracies (with quadratic discriminant analysis) on the order of 99%, comparable to the accuracies achieved with the raw spectral data. The best seven principal components were not those associated with the largest variation in the data. This paper suggests how comparable classification accuracies might be achieved in a system operating at production speeds in a mill