Wood and Fiber Science (E-Journal)
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Technical Note: Impact of Fertilization on Within-Tree Variability in Young Loblolly Pine (Pinus Taeda)
Get PDFDensity, ring width, and cell structure were analyzed at different sampling heights and growth ring numbers in a young loblolly pine tree (Pinus taeda) that had received multiple applications of fertilizer. Results indicated that earlywood and latewood tracheid length increased with increment of growth ring number and height, but fertilization did not appear to measurably influence cell length. As tree height increased, density decreased but latewood cell wall thickness increased. During the fertilization period, ring width and earlywood cell diameter increased, whereas density, latewood cell wall thickness, and latewood percentage decreased. Earlywood cell wall thickness did not appear to be influenced by fertilization and did not vary greatly with increment of growth ring number
Applications of Perpendicular-To-Grain Compression Behavior in Real Wood Construction Assemblies
Get PDFCompression perpendicular to grain (C┴) of wood is an important property and has a drastic effect on serviceability of the structure. Typical C┴ loading scenarios include the bottom chord of a truss resting on the top plate of a shear wall and chords of a shear wall resting on the bottom plate. Present design values for C┴ are based on stress at 1-mm deflection for an ASTM block test. However, in real applications, loading conditions and deflection limits are much different from that administered during the test. There is a need to characterize C┴ behavior of wood in construction applications and compare it with current design codes. This study addresses that by testing two different assemblies involving C┴ loading, each with two different species of wood, to quantify the design C┴ based on the desired application and compare it with current design codes. Also, the effect of species and aspect ratio of assembly was characterized. Results suggested that the ASTM values significantly differ from the assembly values. Species of wood did not have any effect on the performance of the assemblies. A 2% strain offset method was proposed to determine allowable value for C┴ for a desired application. Adjustment factors based on loading configurations were suggested for calculation of design values
Recovery of Mechanically Induced Residual Stresses in Densified Softwoods Created During a Densification Process
Get PDFMechanical densification technology has been used to increase density and mechanical properties of low-density wood. After the densification process, some internal stresses created during densification can be temporally "locked" in wood, which is defined as mechanically induced residual stresses. When the densified wood is exposed to wet conditions, these mechanically induced residual stresses along with swelling stresses can be released with time, which might result in dimensional instability causing warping. This study aimed at examining mechanically induced residual stresses in densified softwoods and simulating the stress-releasing process by means of a mathematical model. Balsam fir and eastern white pine were used for undensified wood specimens and densified wood specimens that were compressed at three compression ratios (CRs) of 0.25, 0.50, and 0.60. Specimens compressed at 0.50 and 0.60 CR plus one control group of undensifed specimens (ie CR = 0) was used to calculate model parameters, and ones at 0.25 CR were used to verify the model developed. Total residual stresses were directly measured by soaking softwood specimens in hot water of 60°C. It was found that 1) about 50% of maximum total residual stress in densified fir and pine specimens could be released in the first several minutes after soaking in the hot water; 2) the mechanically induced residual stresses increased with increasing CR; 3) the mechanically induced residual stresses released from pine were slightly larger than those from fir; and 4) the mathematical model developed in terms of CR could well simulate the release of mechanically induced residual stress with increasing time
Mechanical Properties of Wood-Polypropylene Composites with Industrial Wood Particles of Different Sizes
Get PDFIndustrial wood particles used for manufacturing three-layer particleboards were used to prepare wood-polypropylene composites by an injection molding process. The effect of particle size (0.25-0.5, 0.5-1, 1-2, and 2-4 mm) on mechanical properties of composites was investigated. Additionally, the effect of cross-section size of composite pieces (4 x 10, 6 x 15, and 8 x 20 mm2) was studied. Both particle size and specimen cross-section area significantly influenced these properties. Tensile and mechanical properties as well as impact strength increased with increasing particle size from 0.25-2 mm and then slightly decreased. Flexural and impact strength decreased with increasing cross-section size, whereas variation of tensile modulus and strength and of flexural modulus with increasing cross-section size was different for composites with different particle sizes
Moisture Content Measurement in Scots Pine by Microwave and X-Rays
Get PDFThere is demand in the Swedish sawmill industry to improve the accuracy of moisture content measurements, both to obtain a better tool to run production and to ensure that the products meet customer expectations. In this study, 240 well-conditioned pieces of Scots pine (Pinus sylvestris), sorted into five different groups by visual inspection, were measured using microwaves and X-rays. Models to predict moisture content of wood were made by measurements of an additional 45 pieces of wood. Using only measured quantities from the microwave system, ie attenuation and phase shift, the root mean square error (RMSE) of the estimated moisture content was 1.00%. By adding total density from the X-ray measurements, RMSE of the estimated moisture content was lowered to 0.89%. Mean errors of the different wood groups varied from -0.65 to 0.18%
Bioremediation and Leaching Potential of Pentachlorophenol (PCP) in Biodiesel Versus Diesel Carriers
Get PDFBiodiesel is believed to be more environmentally friendly than petroleum-based diesel when used as a carrier for impregnating wood products with pentachlorophenol (PCP) for decay protection. A 6-mo study was conducted to evaluate bioremediation of PCP in biodiesel vs diesel in soil. Different percentages of biodiesel, diesel, and PCP were mixed with clean soil from a forested site and tested. Samples were taken bimonthly and analyzed for oil and grease, PCP concentration, and microbial enumeration. Soil moisture content was adjusted twice weekly if needed. In addition, toxicity and toxicity characteristic leaching potential were measured at Days 0 and 180. Results showed that with an increase in percentage of biodiesel, there was an increase in degradation of diesel and diesel-amended PCP. The greatest decrease of PCP concentration and toxicity occurred in biodiesel alone by Day 180. Results also showed a significant decrease with time in oil and grease concentration, PCP concentration, and toxicity among different treatments. Based on this study, it appears that the cometabolic effect of biodiesel on micro-organisms could accelerate degradation of PCP in treated wood after disposal
Evaluation of Fungi Toxic Activity of Tannins and a Tannin-Copper Complex from the Mesocarp of Cocos Nucifera Linn
Get PDFThe fibrous envelope of the coconut tree is an agroindustrial waste product that possesses relevant properties, such as a high resistance to biological degradation, because of its phenolic compound composition. In this study, the fungitoxic activity of tannins and a tannin-copper complex from the mesocarp of Cocos nucifera Linn was conducted. An extract from the coconut mesocarp was obtained in acidic media using a 2.0 wt % solution of NaHSO3. Bioassays were conducted on alder wood (Alnus acuminata ssp. glabrata H.B.K.) using two types of aqueous solutions: 1) crude extract from the coconut mesocarp diluted at several concentrations (0.5, 1.0, 2.0, and 4.0 wt %); and 2) a tannin-copper complex formed in two stages by impregnation of the alder wood samples, first with the coconut mesocarp extract solutions followed by addition of a CuCl2 solution. The fungitoxic capacity of the tannin and tannin-copper complex solutions was evaluated by means of bioassays with Trametes versicolor (L. ex. Fr.) Pilát according to ASTM D 1413-07. The bioassays showed poor fungal inhibition for the wood samples impregnated with the crude extract solutions. However, the tannin-copper complex solutions showed greater fungal inhibition. Retention values of 4.03 and 1.76 kg m-3 were obtained. These values revealed high fungal inhibition for Trametes versicolor
Numerical Modeling of the Medium-Density Fiberboard Hot Pressing Process, Part 1: Coupled Heat and Mass Transfer Model
Get PDFA mathematical model describing heat and moisture transfer during hot pressing of medium-density fiberboard mats is presented. The model is based on conservation of energy, air mass, and water vapor mass, resulting in a three-dimensional unsteady-state problem in which mat properties and state variables vary in time and space. The conservation equations are expressed as functions of the three state variables: temperature, air pressure, and vapor pressure. The model includes conductive and convective heat transfer, phase change of water, and convective and diffusive mass transfer. Resin curing kinetics and latent heat associated with phase change of water are also taken into account. The closing of the batch press and development of the density profile are taken into account by imposing a predefined time- and space-dependent density profile. Calculations are carried out on reference geometry, and mathematical details relevant to the transfer from actual to reference geometry are presented. The system is discretized in space by the finite element method and in time by the Euler implicit scheme. The results exhibit good agreement with experimental measurements and provide information on variables of interest such as total gas pressure, temperature, moisture content, RH, and resin cure
Effect of Temperature on Acoustic Evaluation of Standing Trees and Logs: Part 1—Laboratory Investigation
Get PDFThe goals of this study were to investigate the effect of environment temperature on acoustic velocity of standing trees and green logs and to develop workable models for compensating temperature differences as acoustic measurements are performed in different climates and seasons. The objective of Part 1 was to investigate interactive effects of temperature and moisture state of wood on acoustic properties in a laboratory-controlled environment. Small clear specimens (25.4 x 25.4 x 407 mm) obtained from a freshly cut red pine (Pinus resinosa) log were conditioned to four moisture content levels: green (fresh-cut condition), 24%, 12%, and 0%. All specimens were acoustically tested using an ultrasonic device across a temperature range of -40 to 35°C. Results indicate that wood temperature had a significant effect on acoustic velocity in frozen wood. Below the freezing point, acoustic velocity increased as wood temperature decreased. When wood temperature was well above freezing, velocity decreased linearly at a slow rate as wood temperature increased. We found that wood moisture content had a significant compounding effect on velocity-temperature relationships in the freezing zone (-2.5 to 2.5°C). Temperature effect was much more significant in green wood than in dry wood. In green wood, both velocity and peak energy changed abruptly around the freezing point because of the phase transformation of free water in the cell lumens
Phenol Adsorption on Nitrogen-Enriched Activated Carbon from Wood Fiberboard Waste
Get PDFNitrogen-enriched activated carbons were prepared from wood fiberboard waste using 50% potassium hydroxide solution. Activated carbons were obtained with an impregnation ratio (gram chemical agent/gram wood fiberboard waste) of 3 in 850°C activation temperature carbonized for 60 min. Nitrogen content in activated carbon was 1.33% by analysis. Effects of contact time, pH, adsorbent dosage level, and temperature on phenol adsorption capacity of activated carbons were investigated. Adsorption equilibrium was achieved within 100 min at the given phenol concentration of 250 mg/L. When 0.1 g of the carbon absorbent and 100 mL of phenol solution at 250 mg/L were used, maximum adsorption capacity of phenol on activated carbon can reach 207 mg/g. The kinetics of phenol adsorption followed nicely the pseudo-second-order rate expression. In the adsorption isotherm, the Langmuir model fit better than the Freundlich model in phenol adsorption. This study suggests that nitrogen-enriched activated carbon prepared from wood fiberboard waste can be used effectively for removal of phenol compounds from aqueous solutions