Wood and Fiber Science (E-Journal)
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Effects of Isomer Ratio on Pmdi Resin Reactivity and Oriented Strandboard Properties
Get PDFThe effect of varying 2,4'-MDI to 4,4'-MDI isomer ratio in diphenylmethane diisocyanate (pMDI) adhesives was investigated. In addition to probing resin cure kinetics, oriented strandboard panels were produced to investigate the effect of isomer ratio on panel properties. With one exception, differential scanning calorimetry results showed a trend of increasing activation energy with increasing 4,4'-MDI content—the opposite of what was predicted. Results of internal bond testing indicate that increasing 4,4'-MDI content gave higher internal bond strength, but no correlation was evident between resin and panel density, MOR, MOE, or 24-h thickness swell. It is important to note that isomer ratio was not the only variable within the resin series; oligomer content and hence viscosity increased as 4,4'-MDI content increased, which complicated the analysis
Use of Mountain Pine Beetle Killed Wood to Produce Cement-Bonded Particleboard
Get PDFThis study investigated the properties of cement-bonded particleboards made with mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins)-infected wood. Four different types of lodgepole pine (Pinus contorta var. latifolia Engelm.) particles, from two different log sizes and two different years since tree death (3 and 5 yr), were considered in this study. Different formulations consisting of two cement types, two additives, various wood/cement/water ratios, and a range of additive conditions were studied. Mechanical and physical tests were conducted to examine the properties of the specimens. The results showed that wood particles from small logs (diameter < 28 cm) of 3 yr since tree death with either type of cement and calcium chloride or magnesium chloride as the additive are the best formulations. Other formulations also showed comparable mechanical and physical properties to published results of cement-bonded products. Based on the testing results, MPB woods may be used for the manufacture of the value-added wood—cement products
Importance of Temperature, Moisture Content, and Species for the Conversion Process of Wood Residues Into Fuel Pellets
Get PDFIn wood pellet production, knowledge is needed about the raw material properties that affect the energy requirements for pelletizing and pellet quality. This study presents novel methods for this purpose, including analyses of influence of the raw material properties on the energy requirements in the sequence of subprocesses (compression, flow, and friction components) that constitute the pelletizing process, and the strength of the pellets. The methods were used to analyze the importance of pelletizing temperature and MC and the differences between sawdust of European beech (Fagus sylvática L) and Scots pine (Pinus sylvestris L). Results showed that increasing temperature and MC decreased the energy requirements for all components of the pelletizing process and that beech required more energy than pine in all components. Beech produced the stronger pellets; increasing temperature resulted in stronger pellets, whereas increasing MC caused weaker pellets. Also, a method to quantify the energy requirements for the combined pelletizing process is presented. The methods can be used to analyze the allocation of the energy requirements of pelletizing in the die and can be useful tools for analyzing the pelletizing properties of wood and other biomass residues
Treatment of Wood with Polysilicic Acid Derived from Sodium Silicate for Fungal Decay Protection
Get PDFThe aim of this study was to investigate safer, more inexpensive chemicals derived from sodium silicate that can be used to protect wood against fungal degradation. Desiccant and surfactant properties of sodium silicate-derived products have been used since the early 19th century and may find application for wood decay protection. In our study, wood was impregnated with 19.5% sodium silicate and acidified with 2.5% phosphoric acid for 2 da to produce polysilicic acid. After 2-wk daily water leaching, leached specimens had 0.2% weight loss by a brown-rot fungus, Gloeophyllum trabeum, and weight losses of 3.4-5.2% by a white-rot fungus, Trametes versicolor. The control had 32.2 and 30.2% weight losses by G. trabeum and T. versicolor, respectively. Energy-dispersive X-ray analysis showed that polysilicic acid deposited mainly in the cell lumens. Exposure at 90% RH showed that polysilicic acid-treated loblolly pine or sweet gum that had been water-leached with 22-34% chemical retention absorbed more moisture than untreated wood. This indicated that decay resistance of polysilicic acid-treated wood is caused by a different mechanism than desiccation. One possible mechanism may be attributed to direct disruption of permeability of fungal cell membranes by the low-molecular-weight polysilicic acid
Determination of Physical and Mechanical Properties of Finishing Papers Used for Wood-Based Composite Products
Get PDFThere has been a noticeable trend in the furniture and flooring industries in using finishing products (decorative paper, foil, wood veneer, and so on) of different quality on both surfaces of raw engineered wood-based panels. Under variable temperature and RH conditions, this practice can result in dimensional instability. The objective of this study was to determine the key properties of five finishing papers affecting the hygromechanical behavior of wood-based composite panels. The diffusion coefficients, swelling properties, and tensile modulus of elasticity (MOE) of the finishing papers were determined. The results show that the finishing papers studied are anisotropic in terms of their physicomechanical properties. For papers impregnated with melamine-formaldehyde resin, the tensile MOE decreases with an increase in resin content. Swelling is the most significant dimensional change. The range of variation of the linear expansion coefficients is between 0.03 and 0.17 in the fiber direction and between 0.08 and 0.28 in the transverse direction for raw papers. The linear contraction coefficients vary between 0.05 and 0.31 in the fiber direction and between 0.07 and 0.28 in the transverse direction. The behavior is different during adsorption and desorption. Effective diffusion coefficients of the papers tested vary between 4.5 × 10-12 and 8 × 10-11 m2s-1
Hardness Values for Thermally Treated Black Ash
Get PDFThe objective of this study was to analyze the effect of a thermal treatment on the hardness of a Boreal hardwood species. As an undervalued and underutilized tree in Canada, black ash (Fraxinus nigra Marsh.) was selected as one that could potentially benefit from this process. The wood was processed runs in a new high-temperature kiln system being developed in northwestern Ontario, Canada, by Superior Thermowood®. During the processing, the wood deepened in color from a light brown to a darker brown, similar to that of walnut wood. Defect-free samples of Thermowood black ash were collected from two high-temperature runs (200°C wood temperature) and tested for hardness. Using the Janka ball hardness test, thermally modified black ash displayed average hardness values at 8% MC (5700 N), 43% greater than the controls and in the same range as published for untreated wood (5400 - 6000 N). With an improvement in the black ash aesthetic appearance combined with the slight increase in hardness, this species is well suited to be utilized in high-value markets, including flooring and fine furniture
Biotransformation of Tebuconazole by Microorganisms: Evidence of a Common Mechanism
Get PDFA major problem with organic wood preservatives is biotransformation by both wood decaying and wood-inhabiting but nondecaying microorganisms in long-term service. Detoxification of organic biocides may contribute significantly to treated wood failure. In this study, a bacterium (Pseudomonas fluorescens), mold (Trichoderma harzianum), soft rot (Chaetomium globosum), white rot (Phanerochaete chrysosporium), and brown rot (Meruliporia. incrassata) were used to access the extent of biotransformation and the initial metabolite products of tebuconazole in liquid cultures. This study proposed metabolic pathway(s) and explored the possibility of a common biotransformation mechanism for all species. P. chrysosporium showed little ability to metabolize tebuconazole. Within 21 da, 40.4, 59.9, 68.2, and 70.2% tebuconazole was metabolized by M. incrassata, C. globosum, T. harzianum, and P. fluorescens, respectively, into a form that may be less toxic. Mass spectroscopy and infrared analysis of isolated metabolites indicated that the major pathway was cleavage of the triazole ring on tebuconazole and that most species mainly performed oxidation reactions to form the alcohol monolog, which was further oxidized to form the carboxylic acid analog of tebuconazole. Only T. harzianum metabolized the hydroxyl group on the tert-butyl moiety by acetylation to form an ester
Tensile Properties of Earlywood and Latewood from Loblolly Pine (Pinus Taeda) Using Digital Image Correlation
Get PDFThe goal of this research was to measure the elastic properties and strength of earlywood and latewood from two growth-ring positions of loblolly pine. Because of the small specimen size, a contactless strain measurement was applied using a microscope with an appropriate field of view. The tensile properties of the earlywood and latewood were calculated from load data from a Minimat tester coupled with elastic strain data from a digital image correlation technique. Incremental loading was applied until specimen failure occurred. Elastic modulus, Poisson ratio, and strength generally increased as the growthring numbers increased, except for the strength of latewood that slightly decreased. Elastic properties and strength were significantly different for different growth-ring positions and intraring layers. The elastic modulus for earlywood and latewood were best fitted by Weibull distributions regardless of growth-ring positions, whereas Poisson ratios were best fitted by Weibull distributions for earlywood 1 - 10 and latewood 11 - 20 groups, and gamma distributions for earlywood 11 - 20 and latewood 1 - 10 groups. Strain distribution analysis showed nonuniform strain distributions for the four groups and also showed more resistance to load for earlywood and latewood from a higher growth-ring position
