Wood and Fiber Science (E-Journal)
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Laboratory and Field Exposures of FRT Plywood: Part 2—Mechanical Properties
Get PDFOur understanding of how to interpret the laboratory-induced degradation data to real-world in-service performance of fire-retardant (FR) systems is currently limited because we are unable to correlate laboratory steady-state experiments with actual in-service field performance. Current model studies have generally been limited to isothermal rate studies with selected model FR chemicals. Other factors also play a major role in the degradation of FR-treated wood. These factors, which have not been studied in any detail, include RH/MC cycles and thermally induced evolution of ammonia from ammonium phosphates to provide phosphoric acid. Because there exists no known direct comparison of matched samples with one exposed to high-temperature laboratory conditions and the other exposed for an extended period of time as traditionally used in North American light-framed construction, the objective of this study was to determine the relationship for FR model compounds between laboratory and field results based on strength-temperature-RH (MC)-FR chemical interactions. The impact of the variables was evaluated by measuring bending strength properties and comparing matched laboratory and field exposure samples. The physical test data show the positive effects of adding a buffering system to model FR compounds when exposed to high moisture environments and the negative effects of increasing the moisture in the in-service environment during exposure
Effect of Cutting Width and Cutting Height on the Surface Quality of Black Spruce Cants Produced by a Chipper-Canter
Get PDFThe effects of the cutting height and cutting width on the surface quality of black spruce cants produced by a chipper-canter were evaluated. Three diameter classes (102, 152, and 203 mm dia as measured at the small end of the log) were studied, each processed using two cutting widths (12.5 and 25 mm). The rotation and feed speeds, kept constant at 783 rpm and 197 m/min, respectively, yielded a nominal feed per knife (chip length) of 31.5 mm. Twelve logs for each cutting condition were processed under frozen and unfrozen wood temperatures (winter and summer). The surface quality was analyzed using roughness and waviness standard parameters. Torn grain was evaluated by means of its maximum depth. The results showed that surface quality was affected by cutting height, cutting width, and temperature of logs. In general, surface quality was better when processing unfrozen logs at lower cutting width and height. Surface quality also varied within the cant, being generally better at the small end of the log and at the upper part of the cant. The results give useful information to improve the performance of the chipper-canter in terms of surface quality
Effect of Ambient Pressure on Equilibrium Moisture Content of Wood
Get PDFThe equilibrium moisture content (EMC) of Russian larch wood, Sugi wood, and Hinoki wood was measured under vacuum conditions at temperatures of 45, 50, and 60°C and ambient pressures of 13.3, 53.3, and 101.3 kPa. The results show that the EMC of each species increased with a decrease in ambient pressure. The effect of temperature and RH on EMC under vacuum conditions showed a similar tendency. Wet-bulb temperature needed to be controlled to measure EMC, even under vacuum, because pressure was not maintained only by water vapor pressure because of the presence of air in the vessel. There were obvious differences between the EMC values obtained in this experiment and previous experimental EMC values in which the wet-bulb temperature was not controlled
Selected Volatile Organic Compound Emissions and Performance of Oriented Strandboard from Extracted Southern Pine
Get PDFThe impact of a hot water extraction procedure on select volatile organic compound emissions during pressing, as well as on properties of oriented strandboard (OSB) was evaluated. Southern pine strands were extracted with hot water using a rotating digester at 160°C for 22.9 or 53.6 min. Weight loss for the two extraction conditions was 6.3 ± 0.1% (short time) and 9.3 ± 0.9% (long time). The extract contained a mixture of hemicelluloses, acetic acid, and lignin. OSB panels were manufactured both with and without adhesive. The emissions (phenol, methanol, acetaldehyde, and formaldehyde) without adhesive present decreased from 38.2 to 24.2 mg/kg (oven-dry wood) as a result of the high severity factor (HSF) extraction. When adhesive was used, emissions totaled 22.1, 17.0, and 15.6 mg/kg (oven-dry wood) for control, low severity factor, and HSF, respectively. Water sorption and thickness swell were significantly reduced in panels made from extracted strands. Flexural modulus of elasticity of extracted panels exhibited significant increases in both dry and wet conditions. The flexural modulus of rupture and internal bond were slightly reduced in the dry condition as weight loss increased. The extraction procedure shows promise for improving a variety of properties of OSB, including performance, reduced environmental impact, and generation of a valuable chemical feedstock byproduct
Effect of Pretreatment of Bagasse Pulp on Properties of Isolated Nanofibers and Nanopaper Sheets
Get PDFNanofibers were isolated from bagasse pulp pretreated with dilute hydrochloric acid, dilute sodium hydroxide, cellulase, or xylanase enzymes using high-shear ultrafine grinding and high-pressure homogenization. The effect of the different pretreatments on chemical composition and structure of isolated nanofibers was studied using chemical analyses, X-ray diffraction, and Fourier transform infrared. The dimensions and properties of the isolated nanofibers were followed at the different processing stages using optical microscopy, transmission electron microscopy, atomic force microscopy, and tensile properties (wet and dry). The diameter of the microfibrils was in the range of 7-30 nm for untreated and pretreated bagasse pulps while larger microfibrillar bands (to 150 nm wide) were observed for untreated bagasse pulp than the pretreated pulps (to 90 nm wide). Nanopaper sheets made from nanofibers isolated from alkali- and xylanase-treated pulps showed better wet and dry tensile strength than those made from the other pulps
Feasibility of Using Mountain Pine Beetle-Attacked Wood to Produce Wood-Plastic Composites: Preliminary Work
Get PDFThis study investigates the feasibility of using mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins)-killed lodgepole pine (Pinus contorta var. latifolia Engelm) to manufacture wood- plastic composites (WPCs). Preliminary formulations of various flour sizes (20, 40, 60, and 80 mesh), wood contents (40, 50, and 60%), and corresponding contents of high-density polyethylene (HDPE) without additives were used to make strip-like specimens. Extrusion and injection molding were performed to fabricate specimens for investigation of mechanical properties. A simple tensile experiment was conducted to select an appropriate formulation. The injection-molded MPB-wood-HDPE composites resulted in properties that were comparable with a commercial product and other similar studies. MPB wood showed great potential to be a raw material of WPC products
Predicting Bending Stiffness of Randomly Oriented Hybrid Panels
Get PDFThis study was conducted to develop a simple model to predict the bending modulus of elasticity (MOE) of randomly oriented hybrid panels. The modeling process involved three modules: the behavior of a single layer was computed by applying micromechanics equations, layer properties were adjusted for densification effects, and the entire panel was modeled as a three-layer symmetric composite using laminate theory. The model accounts for panel vertical density distribution and the inclusion of two fiber reinforcements. Model inputs were experimentally determined from physical and mechanical tests on hot-pressed resinated strands and bark. Experimental verification was conducted using laboratory panels of wood strands and bark from fire-impacted trees at an 80:20 wood:bark weight ratio. Comparisons with experimental data showed that MOE of hybrid panels was adequately predicted with deviations of 13-23% compared with observed MOE. Results validated application of micromechanic equations and laminate theory to predict the MOE of randomly oriented hybrid oriented strandboard of wood strands and bark. This study also contributes to the knowledge of predicting and tuning stiffness properties of hybrid panel-based composites, thereby promoting utilization and sustainable use of plant-based raw materials
Laminated Wood-Ceramics Prepared from Beech Veneer and Phenol Formaldehyde Resin
Get PDFLaminated wood-ceramics were created from beech veneer by impregnation with phenol formaldehyde resin and airtight sintering. The resulting laminated biocarbon material exhibited a clearly layered structure and partially preserved microstructural characteristics of normal wood. Laminated structure and airtight sintering techniques significantly affected basic material properties. Carbon yield can increase and sintering cost can decrease through these methods. The material treatments used generate porosity, density, and volumetric shrinkage properties that are different from composites that are vacuum-sintered. Its layered structure is associated with the stacking of veneers. The fracture toughness increases to 0.6-1.2 MPa·m1/2 because of the laminated structure, and the material exhibits a progressive failure behavior
Dynamic Sorption and Hygroexpansion of Wood Subjected to Cyclic Relative Humidity Changes
Get PDFTo investigate the behavior of sorption and hygroexpansion of wood at nonequilibrium, Sitka spruce (Picea sitchensis Carr.), 4-mm along the grain and 20-mm in radial and tangential directions, was exposed to sinusoidally RH between 45-75% at 20°C for 1, 6, and 24 h. Moisture changes and radial and tangential dimensional changes measured during the cycling gave the following results: moisture and dimensional changes of the specimens were generally sinusoidal but lagged behind the imposed RH. The phase lag decreased and amplitude increased with increasing cyclic periods. Furthermore, a mathematical model proposed in a previous study was modified to describe the dynamic sorption of wood exposed to cyclical RH. The model not only produced kinetics in good agreement with experiment results, but also can provide moisture gradient distributions developed throughout the wood during cyclical processes