Wood and Fiber Science (E-Journal)
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A Review on Promising Approaches for Liquid Permeability Improvement in Softwoods
Get PDFThe low liquid permeability of refractory wood species such as Norway spruce [Picea abies (L.) Karst.] and white Fir (Abies alba) is related mainly to the aspiration of bordered pits during wood drying. The resulting low permeability complicates treatments with liquid preservatives or wood modification substances. This article provides a literature review on various mechanical and biotechnological approaches that were developed for improving liquid permeability. In this context, we focus on the incubation of Norway spruce wood with a white rot fungus, Physisporinus vitreus (Pers.) P. Karst. The process is termed "bioincising" and results in a significant increase in wood permeability. This is most probably caused by the selective degradation of bordered pit membranes and simple pits of xylem ray parenchyma during the initial period of wood colonization. Subsequently, we discuss how bioincising could be a potential pretreatment method for wood preservation and selected wood modification substances. Considering that these wood modification systems require specific penetration depths for optimal performance, we discuss the capability of bioincising to enhance permeability at the required penetration depths. In this regard, we propose a terminology for better differentiation of penetration depths by liquid substances into the wood
Variability of Wood Color in Paper Birch in Québec
Get PDFColor variability of paper birch (Betula papyrifera Marsh.) wood at the tree level was examined in this article. Tree age, dimension, and vigor were expected to influence the proportion of discolored wood in paper birch boards; older, larger, and less vigorous trees were assumed to produce boards with higher proportions of discolored wood. The color analysis was performed on approximately 2250 boards produced from 168 paper birch trees harvested in two different stands from which only logs of sawing quality were used. An industrial scanner was used to digitize the boards and obtain colorimetric information. Results show that tree diameter and vigor significantly influenced the proportion of discolored wood in boards, whereas the effect of tree age did not have a significant influence in the model. An average area of 32.4% of discolored wood was obtained when considering all boards. Less vigorous trees showed a mean area of 45.32%, whereas middle-vigor and most-vigorous trees had mean areas of 30.78 and 15.47%, respectively. The colorimetric values were mainly affected by tree age and diameter, but these effects were variable for every colorimetric parameter. The analysis of the random effects demonstrated that most of the total random variance of the dependent factors came from the between-board, between-tree, and, to a lesser extent, between-log variation. These findings suggest that favoring shorter rotations would help produce trees with lower proportions of discolored wood
Decay Resistance Properties of Hot Water Extracted Oriented Strandboard
Get PDFThe use of extracted wood hemicelluloses as a substrate for fermentation and biofuels production has the added benefit of leaving the remaining wood product intact after extraction and being usable in other applications. However, it is still unclear how these extraction procedures might affect susceptibility to fungal attack. Modified oriented strandboards (OSB) were created by hot water extracting red maple strands before adhesive application and pressing of the strands into boards. Treated and untreated boards were tested for decay susceptibility in a modified ASTM soil block jar bioassay using multiple species of white and brown rot fungi. Results showed no significant differences in decay susceptibility between the untreated and extracted boards for all the brown rot fungi tested. The white rot fungi tested were shown to decay the boards made from extracted strands significantly less than the boards made from control strands. These results indicate that modifying OSB panels by removing hemicelluloses for use in ethanol and other alternative fuel production does not increase decay susceptibility to the brown rot fungi tested and appears to confer a degree of decay resistance against the white rot fungi
Monotonic and Cyclic Load Testing of Partially and Fully Anchored Wood-Frame Shear Walls
Get PDFThe objectives of this study were to evaluate the performance of wood-frame shear walls under monotonic and cyclic loads by: 1) determining variability of shear wall performance; 2) comparing performance of walls under each loading protocol; 3) evaluating effects of anchorage on wall performance; and 4) evaluating performance of walls qualitatively and quantitatively with respect to codedefined performance measures. Sets of tests consisting of eight partially and two fully anchored walls were conducted using both the ASTM E564 monotonic protocol and CUREE cyclic-test protocol for ordinary ground motions for a total of 20 walls. Statistical comparisons of parameter variance and mean values were made between partially anchored walls tested under different protocols and performance comparisons were made between partially and fully anchored walls. Cyclic tests on partially anchored walls generally exhibited a coefficient of variation that was lower than for monotonic tests. Failure mode of fully anchored walls was different than that for partially anchored walls because hold-downs changed the load path. Comparison of test results with ASCE 41 m-factors suggests that ductility of partially anchored walls is below the acceptance criteria for shear walls with structural panel sheathing
Acoustic Tomography for Decay Detection in Black Cherry Trees
Get PDFThis study investigated the potential of using acoustic tomography for detecting internal decay in high-value hardwood trees in the forest. Twelve black cherry (Prunus serotina) trees that had a wide range of physical characteristics were tested in a stand of second-growth hardwoods in Kane, PA, using a PiCUS® Sonic Tomograph tool. The trees were felled after the field test and a disc from each sampling height was cut and subjected to laboratory evaluations. It was found that acoustic tomography underestimates heartwood decay when it is the major structural defect in the trees. However, when an internal crack is present in the tree trunk, the acoustic tomography tends to overestimate the size of the defects. In the presence of ring shake in the cross-section, the acoustic shadows resemble the influence of both extensive heartwood decay and lateral cracks. These findings highlight the importance of determining the nature of structural defects when assessing hardwood trees using the acoustic tomography technique. Results from this study offer insights that may be used to improve the interpretation algorithm embedded in the tomography software
The Influence of Cutting Parameters on the Surface Quality of Routed Paper Birch and Surface Roughness Prediction Modeling
Get PDFThe objective of this study was to characterize the routing process to better understand the machining conditions that affect surface finish. Experiments were designed to determine the impact of cutting depth, feed speed, and grain orientation of the workpiece on the surface quality of paper birch wood. Statistical analysis showed that the cutting depth did not influence surface finish. Roughness depended greatly on feed speed and grain orientation, increasing linearly as the feed speed increased. The roughest surfaces were obtained by routing against the grain between 120 and 135° grain orientation, depending on the feed speed. Two models able to predict the surface finish based on initial cutting parameters were developed and compared. Both the statistical regression and neural network models were subjected to a validation procedure in which their performance was confirmed using data that were not used for the learning process. Results indicated that the neural network system estimates the surface roughness with less error than the statistical regression model
Effects of Cambial Age and Stem Height on Wood Density and Growth of Jack Pine Grown in Boreal Stands
Get PDFJack pine specimens were examined for longitudinal and radial variations in selected wood quality parameters. Wood density and ring width of cross-sections were measured systematically from pith to bark along the merchantable stem using X-ray densitometry. Effects of cambial age and stem height were analyzed using a linear mixed model with two levels of nesting. A strong interaction between the two factors was found in corewood. Tree individual variation increased with cambial age for all studied wood properties and was larger in earlywood than in latewood. Radial patterns in the studied parameters closely approximated published ones in the lower stem but lessened considerably with increasing stem height. By contrast, longitudinal patterns reversed with cambial age in earlywood. High coordination was found between longitudinal patterns in corewood and radial patterns in the stem base, indicating a similar maturation pattern in the apical meristem and cambia. However, with increasing cambial age, this high coordination disappeared rapidly
In Situ Thermal Condensation of Glucose-Diammonium Phosphate Inwood for Fire and Fungal Decay Protection
Get PDFThermal condensation of glucose-diammonium phosphate in wood at 160 and 190°C will protect wood against fire and decay in one treatment using an aqueous system. For fire protection, treatments at 160 or 190°C led to low flammability as evidenced by fire-tube tests. For nonleached wood, weight losses were 1.9, 2.0, and 2.0% with chemical retentions of 56.7, 44.7, and 64.7%, respectively, for 2-, 4-, and 6-h heating; and for leached wood, weight losses of 5.1, 3.8, and 1.5% with chemical retentions of 24.5, 24.1, and 45.6%, respectively, for 2-, 4-, and 6-h heating compared with 18.8% weight loss for diammonium phosphate-treated wood with chemical retention of 19.4%. The control had 84.4% weight loss. For decay protection, heat treatment at 190°C for 30 min after 2-wk water leaching also prevents degradation by brown and white rot fungi. Weight loss by Gloeophyllum trabeum (Gt) was 0.4% with 19.5% chemical retention, and weight loss by Trametes versicolor (Tv) was 1.5% with 17.8% chemical retention. The control had 30.6 and 36.8% weight losses by Gt and Tv, respectively
Effects of Sintering Conditions on Microstructure Changes of Wood-Ceramics Impregnated with Low-Molecular-Weight Phenol-Formaldehyde Resin
Get PDFThe microstructure of a new type of wood-ceramics made from poplar fiber impregnated with low-molecular-weight phenol-formaldehyde (PF) resin under atmospheric pressure was studied under changing sintering conditions. X-ray diffraction analysis indicated that the d002 value was reduced with increasing sintering temperature. The wood-ceramic structure also became more uniform and orderly, but still was nongraphitic carbon. Scanning electron microscopy showed that the pore structure partially retained the microstructural characteristics of wood fiber, and a graphitic phase was formed with increased sintering temperature and longer holding time. All analyses showed PF resin molecular weight had little impact on phase composition and graphitization. The apparent specific gravity of woodceramics increased as sintering temperature increased to 1200°C but decreased as temperature rose further. Specific surface area and apparent porosity were increased with higher sintering temperature, greater sintering rates, and longer holding times. In addition, specific surface area was also affected by the molecular weight of PF resin and the impregnation method, in which low-molecular-weight resin increased the specific surface area
Technical Note: Equilibrium Moisture Content of Norway Spruce at Low Pressure
Get PDFThe EMC of Norway spruce (Picea abies) was determined at various levels of temperature and RH under low pressures. EMC corresponded to temperature and RH and was strongly related to vapor pressure inside the chamber. The amount of air present in the vacuum chamber did not significantly affect the EMC. The Hailwood-Horrobin model can be used to estimate the EMC of wood under vacuum, although it is about 2-3% MC less than the actual EMC of wood during initial desorption