Wood and Fiber Science (E-Journal)
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The Effect of Cyclic Relative Humidity Changes on Moisture Content and Thickness Swelling Behavior of Oriented Strandboard
Get PDFThis study examines the effect of cyclic RH exposure on MC and thickness swelling (TS) of oriented strandboard (OSB) made from fire-impacted trees. Two specimens were cut from the center of each OSB panel and one was edge-sealed. After being conditioned to 65% RH, specimens were placed in a climate-controlled chamber and subjected to three cyclic changes of 90 - 30% RH at 20°C. Experimental data were characterized by three time-dependent MC or TS models: logarithmic, power law, and exponential. The latter two models gave the best fits showing that edge-sealing reduced the extent of swelling during adsorption and reduced the moisture loss at desorption. The models also described the effect of burnt level and bark throughout the humidity exposure cycles. The exponential model revealed no significant effect of burnt level on the panel TS. Both the power law and exponential models indicated that addition of charred bark to the panels significantly decreased the maximum amount of moisture and thickness change. The exponential model revealed an increase in equilibrium TS at the end of each RH cycle compared with the end of precyclic desorption. True nonrecoverable TS was difficult to discern in Cycle 1 because of moisture hysteresis, but the nonrecoverable effect was evident in Cycles 2 and 3
Wood and Lumber Properties from Unthinned and Precommercially Thinned Black Spruce Plantations
Get PDFThis study examined wood and lumber bending properties of 44-yr-old plantation black spruce subjected to precommercial thinning (PCT) at age 23. PCT and tree diameter at breast height (DBH) had little effect on heartwood content and the No. 2 & Better lumber grade yield. With increasing DBH of 10 - 18 cm, basic wood density (Db), lumber bending modulus of elasticity (MOE), and modulus of rupture (MOR) decreased by 8.1, 15.8 and 19.0%, respectively. The Db, MOE, MOR, and machine stress-rated (MSR) lumber yield from the stand with 35% basal area removal (T35) were lower than those of the control (T0) and the stand with 20% basal area removal (T20). The T20 had no significant effect on the Db, MOE, MOR, and MSR lumber yield. Juvenile wood content had a negative effect on lumber bending properties. The percentage of lumber pieces complying with the design values decreased with increasing thinning intensity. On average, MOE from T0, T20, and T35 were 10.9, 12.1, and 19.5% lower, respectively, than that from mature natural black spruce stands and 19.6, 18.0, and 10.8% higher, respectively, than that from wider-spaced black spruce plantations. MOE from T0 was also 14.5% higher than that from 50 - 60-yr-old natural jack pine stands. This study indicates that it is possible to produce high-quality lumber from dense black spruce plantations with appropriate thinning
Effect of Preservative Type and Natural Weathering on Preservative Gradients in Southern Pine Lumber
Get PDFThe effects of preservative type and natural weathering on preservative component distribution in southern pine boards were evaluated. Lumber was treated by a modified full-cell process with chromated copper arsenate (CCA-C), alkaline copper quat (ACQ-D), and micronized copper quat (MCQ), and samples were exposed to natural weathering. After treatment, the copper and arsenic components of CCA were uniformly distributed across the board thickness, whereas the chromium component was higher near the surface. The copper amine component of ACQ was preferentially adsorbed near the board surface, whereas MCQ had lower copper concentration near the surface compared with inside the board. The quat component (didecyldimethylammonium carbonate [DDACb]) of both preservatives was preferentially adsorbed near the surface resulting in a steep concentration gradient. After 330 da of exposure to natural weathering, the average amounts leached were 2.9% for ACQ-Cu, 0.36% for MCQ-Cu, 0.24% for CCA-Cr, 0.59% for CCA-Cu, and 2.05% for CCA-As. For ACQ and MCQ, the ratio of CuO to quat increased significantly with weather exposure indicating a higher DDACb rate of leaching compared with copper. For both preservatives, it was estimated that DDACb leaching was about 20% for ACQ and 16% for MCQ
Radial Variation of Rays in two Commercial Softwoods Grown in Korea
Get PDFRadial variation of the height and number of uniseriate and fusiform rays within the stems of two typical Korean softwoods, Pinus koraiensis and Larix kaempferi, was studied. The average height of uniseriate rays was about six cells in Pinus koraiensis and nine cells in Larix kaempferi. The height of fusiform rays, including radial resin canals, was on average 20 cells in both species. The height of fusiform rays was greater than that of uniseriate rays: about 3.2 times for Pinus koraiensis and about 2.3 for Larix kaempferi. The height of uniseriate and fusiform rays was lowest near the pith and increased with age to about ring 10 - 20 and then became constant toward the bark. The number of uniseriate rays in a 0.5 × 0.5 mm area was about 6.5 for Pinus koraiensis and 9.5 for Larix kaempferi. The number of uniseriate rays was at a maximum near the pith and decreased to about ring 10 - 20 and was nearly constant for subsequent rings. The ratio of fusiform to uniseriate rays was 1:45 in Pinus koraiensis and 1:53 in Larix kaempferi. Consequently, it was considered that the results obtained might provide useful information for evaluating juvenile and adult wood as well as identifying both species
Use of Nanoindentation and Silviscan to Determine the Mechanical Properties of 10 Hardwood Species
Get PDFThe objectives of this study were to investigate the properties of bulk wood and cell walls of 10 hardwoods, Alder Birch (Betula spp.), Asian White Birch (Betula platyphylla spp.), Manchurian Ash (Fraxinus mandshurica spp.), Mongolian Oak (Quercus spp.), Poplar (Populus spp.), Red Oak (Quercus spp), White Oak (Quercus spp.), Iroko (Chlorophora excelsa spp.), Keranji (Dialium spp.), and Kwila (Intsia spp.). The relationship between wood species and mechanical properties as well as the relativity of wood species and microfibril angle to the hardness and elastic modulus were investigated. It showed that lower density hardwoods had higher microfibril angle than higher density hardwoods. The elastic moduli of bulk wood and cell walls of wood were both significantly different, whereas the hardness of the cell wall was not significantly different among the 10 species. The SilviScan elastic modulus increased with wood density and decreased with microfibril angle. At the cell wall level, the elastic modulus and hardness obtained by nanoindentation were more related to the properties of natural libriform fibers. However, there was no significant trend found for the hardness of the cell wall as affected by either wood bulk density or microfibril angle
Technical Note: A Preliminary Study on the Bending Stiffness of Chemically Treated Wood Material for Structural Composite Lumber
Get PDFThis research explored the effect of a chemical treatment on the stiffness of three southern hardwoods, yellow-poplar, sweetgum, and red oak, with the aim of broadening the potential feedstocks for structural composite lumber. Water-saturated 3 × 15 × 150 mm samples from each species were heated at 150° C for 30 min in three solutions: 1.0% H2SO4, water, and 1.0% NaOH. The specimens were nondestructively tested by static bending before and after treatment, and the reduction in modulus of elasticity (MOE) was determined. A significant interaction was present between the species and solutions. The trend in mean response for each species was generally a quadratic function of the solution. MOE was reduced the least for each species exposed to water. Sweetgum had a higher reduction in MOE in all three solutions, being significantly greater in the alkaline solution
Ultrasonic Atomization of pMDI Wood Resin
Get PDFA novel, patent-pending approach to the application of wood resins based on an ultrasonic principle was developed in this study. Liquid polymeric methane diphenyl-diisocyanate (pMDI) resin was successfully atomized using a bench-scale 25 kHz ultrasonic atomizer. The optimal average sizes of the resin droplets generated at a flow rate of 0.7 mL/min and power input of 5.0 J/s were about 90 μm. In addition to fewer fine droplets than that produced by conventional spinning-disk atomizers, the droplets of pMDI resin produced by the ultrasonic atomizer had a more uniform droplet size distribution. These results indicate the potential advantages of implementing ultrasonic atomization in oriented strandboard production, including elimination of the hazardous fraction of fine resin droplets and potential production cost savings from improved resin efficiency. The ultrasonic atomization of wood resins appears to be a promising alternative to the spinning-disk atomizer
Assessment of Appalachian Hardwood Residue Properties and Potentials for Bioenergy Utilization
Get PDFLogging residue specimens of yellow-poplar and red oak were collected from 15 previously harvested sites across West Virginia. Sites were selected with respect to the varying soil compositions based on a USDA soil survey as well as to the average annual precipitation regions. Wood specimens were then analyzed for their physical, chemical, and thermal properties. Results indicated that logging residues of yellow-poplar and red oak were dried in nature to 7.4 - 39% MC. Yellow-poplar sapwood-specific gravity reduced by 15 and 26.5% on average after 2 and 3 yr of ground contact, respectively. Red oak sapwood-specific gravity was lower than its heartwood by 26.6, 25.3, and 8.2% for the 2005, 2006, and 2007 harvest years, respectively. Chemical analysis showed higher extractives and lignin contents for decayed wood samples collected in 2005 harvested sites. Heating value showed no significant difference between sapwood and heartwood residues of undecayed and decayed material. Our analysis on the potential sugars available showed that about 85 - 90% of 1.02 billion kg of sugars derivable from wood residues in West Virginia could be fermented to ethanol or butanol
Relationships Among Foliar Phenology, Radial Growth Rate, and Xylem Density in a Young Douglas-Fir Plantation
Get PDFWe related intra-annual patterns in radial growth rate and xylem density to foliar phenology and second growth flushes in a young Douglas-fir plantation in western Washington. Three foliar maturity classes were defined: (1) shoots and needles elongating; (2) elongation complete, needles maturing; and (3) needles mature. Diameter growth rate had two peaks, one about the time of budbreak and one when foliage was in maturity Class 2. There was a limit to the maximum periodic density of xylem formed at a given rate of diameter growth; as growth rate increased, maximum periodic density decreased. Although xylem density profiles varied widely among individual trees, xylem density differed significantly among foliar maturity classes, increasing 16% from Class 1 to 2 and 60% from Class 2 to 3. Diameter growth rate of second-flushing trees was significantly greater in July compared with trees with no second flush, but we detected no relationships between second-flushing and xylem density patterns or false rings. Although the young trees in this study did not show distinct earlywood-latewood transitions, fully mature foliage (Class 3) was associated with formation of xylem exhibiting characteristics of latewood: greater density, reduced diameter growth rate, reduced tracheid radial diameter, and less interannual growth variation