Wood and Fiber Science (E-Journal)
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We Don't Make Wood, We Make Wood Better: Comments accompanying receipt of the 2008 SWST Distinguished Service Award
Get PDFEffect of Strand Geometry and Wood Species on Strandboard Mechanical Properties
Get PDFThis study compared the performance of strandboards made from trembling aspen, a lowdensity hardwood species, with strandboards made from paper birch, a medium-density hardwood species. Strands were cut into three different lengths (78, 105, and 142 mm) and two thicknesses (0.55 and 0.75 mm) to compare the impact of species, strand geometry, specific surface, and slenderness ratio. Internal bond (IB), modulus of elasticity (MOE), and modulus of rupture (MOR) for flatwise and edgewise bending, compressive strength, and stiffness were all determined. Both species performed equally well in IB (0.73 MPa for both species combined). The highest MOE and MOR values in flatwise and edgewise bending were obtained for long, thin strands and were significantly lower for birch than for aspen panels (flatwise: 13.6 GPa and 99.2 MPa for aspen and 12.1 GPa and 85.5 MPa for birch; edgewise: 13.5 GPa and 66.3 MPa for aspen and 13.2 GPa and 65.7 MPa for birch). Short aspen strands resulted in the highest compressive properties, slightly higher than those of short birch strands (aspen: compressive strength 10.4 MPa and stiffness 1.22 GPa; birch: 10.8 MPa and 2.25 GPa, respectively). Strand length must therefore be a compromise between the need for high bending properties provided by long strands and the need for high compressive properties provided by short strands
Moisture in Untreated, Acetylated, and Furfurylated Norway Spruce Monitored During Drying Below Fiber Saturation Using Time Domain NMR
Get PDFUsing time domain-nuclear magnetic resonance spectroscopy, the moisture content (MC) in Norway spruce [Picea abies (L.) Karst.] sapwood, subjected to three different treatments (untreated, acetylated, and furfurylated), was studied during drying at 40°C at MCs below fiber saturation. Spin-spin relaxation time distributions were derived from Carr-Purcell-Meiboom-Gill relaxation curves using mulitexponential fitting (CONTIN). After conditioning for 6 wk at 100% RH, the modified wood samples had a MC of about 15%, whereas the MC of the untreated samples was about 30%. Two water populations with different relaxation times were found in all three sample types at this point: 1.1 ms and 0.15 ms (untreated), 0.5 ms and 0.15 ms (furfurylated), and 1.2 - 3.5 ms and 0.1 ms (acetylated). As the MC decreased, the relaxation time of the most slowly relaxing population decreased, whereas it remained more or less constant for the other population. For both the untreated and the furfurylated samples, the two populations merged at 5 - 10% MC, and relaxation times were identical for the two treatments at low MC. The two populations did not merge for the acetylated samples. These results indicate that while acetylation changed the interaction between water and the wood cell wall, furfurylation seemed to mostly affect the amount of water present within the cell wall at the beginning of the drying experiment
Effect of Fungal Attack on Maximum Load Capacity of Simulated Wall Assemblies
Get PDFThe effects of moisture intrusion and fungal attack on the maximum load capacity of nailed assemblies was investigated using one white- and one brown-rot fungus against four material combinations over a 35-wk period. Wetting significantly reduced the maximum load capacity of all four material combinations, whereas wetting and autoclaving only affected the oriented strandboard (OSB) sheathing/spruce stud assembly. The white-rot fungus (Trametes versicolor) had no significant effect on the maximum load, whereas the brown-rot fungus (Gloeophyllum trabeum) produced significant load reductions on shear connector assemblies with OSB sheathing. Results indicate that moisture remains the dominant initial factor in the performance when water intrudes into wall assemblies
Empirical Distribution Models for Slenderness and Aspect Ratios of Core Particles of Particulate Wood Composites
Get PDFParticle geometry was characterized for particleboard furnish prepared through hydrolysis of finished commercial particleboard procured from six Canadian plants. Particles samples were screened into seven particle size classes. Particles retained on 0.5-mm mesh were considered core particles and further partitioned into core-fine, medium, and coarse. Individual particles were then randomly selected for geometrical characterization and distribution fitting. About 80% of all screened particles by mass were between mesh sizes of 0.5 and 2 mm. There were significant differences in percentage screen masses of all particle sizes between plants. Masses of particle size greater than 1 mm of panels from two plants were significantly higher than the rest (0.05 α-level), whereas another plant had the highest mass of particle sizes retained on the 2-mm mesh. Particles retained on the 1-mm mesh showed the largest percentage mass variation among all plants. It was found that aspect ratio was a better geometrical indicator for predicting screw withdrawal resistance than any of the absolute dimensions, and increase in core-fine particles increases internal bond strength. Based on maximum likelihood and Akaike's Information Criterion, a log normal distribution was the best fit for all geometrical descriptors of most particle types; gamma and two-parameter Weibull were better fits for length and aspect ratio for most medium particles with gamma being the better of the two
Thermal Degradation and Thermal Conductivity of Gypsum-Cement Particleboard
Get PDFThermal degradation of boards made from wood particles mixed with gypsum and gypsum-cement was determined in air and nitrogen by thermogravimetric analysis. The pure constituents of the boards (wood particles, gypsum, and Portland cement) were characterized separately. The thermal conductivity of the boards was determined using a heat flowmeter apparatus. Commercial gypsum board was used as a control for all the tests performed. Commercial gypsum board, pure gypsum, pure Portland cement, and gypsum-cement mixture showed mass losses between 18 and 22% at 800°C. Conversely, the wood particles were very sensitive to heat in the presence of air. In general, gypsum-cement particleboard exhibited better resistance to thermal degradation than gypsum particleboard, but it has the highest thermal conductivity as a result of its higher density. Thermal conductivity was shown to be strongly dependent on board density
Surface Energy Modification by Radiofrequency Inductive and Capacitive Plasmas at Low Pressures on Sugar Maple: An Exploratory Study
Get PDFThe wood products industry is going through hard times in both Canada and the US. It is faced with competition from emerging economies and substitution products. The North American economy is slowing down with decreasing demand for wood products. Under these conditions, the industry should be innovative and develop the next generation of wood products. Plasma technology could be used to improve wood surface properties and compensate for the variations to be expected from an organic living material, which is sensitive to its environment (moisture, water, temperature, ultraviolet light). In recent years, the plastic and textile industries have begun experimenting with plasma technology to activate surfaces, mainly to improve coating/substrate adhesion. The literature on potential applications of plasma treatment to wood surfaces is very limited. This report describes the results of an exploratory study on the effect of plasma treatments on sugar maple wood using different gases and mixtures (N2, H2, O2, and Ar) at different pressures (13.3-665 Pa). Water wettability and adhesion between surface and waterborne polyurethane acrylate coatings were also studied. The results show that it was possible, under certain conditions, to significantly increase wood/coating adhesion by 30-100%. This improvement is correlated with improvements in wood surface energy and coating penetration depth. In addition, chemical analyses showed that, with some plasma types, the treatment led to new atoms being grafted