Wood and Fiber Science (E-Journal)
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Southern Pine Wood and Strands Impregnated with Low Levels of Butanetetracarboxylic Acid as Stabilizing Agent for Oriented Strandboard
Get PDFSouthern pine wood specimens were impregnated with butanetetracarboxylic (BTCA) acid at 1.0-5.0% levels using a vacuum/pressure method and hot-pressing at 150°-210°C in the radial direction. The acid treatments gave anti-swelling efficiency (ASE) values up to 57% in an exhaustive first water-soak cycle. The ASE values were higher in the radial than tangential direction, and higher for irreversible than reversible components. Laboratory strandboards made with wood strands impregnated with 0.5°-1.0% BTCA levels under vacuum showed ASE values of up to 53%, but internal bond and modulus of elasticity and rupture values decreased somewhat excessively. The strength values of boards were modest, higher than the minimum industry requirements for commodity-type oriented strandboard. The various effects of BTCA on wood and board properties were discussed. Use of BTCA at less than 0.5% level and optimization of hot-pressing and resin binder and wax levels may result in a method of manufacturing oriented strandboard with significantly improved dimensional stability
Fungi and Decay in Western Redcedar Utility Poles
Get PDFThree decay fungi were isolated from the heartwood and six from the sapwood of western redcedar poles. None had previously been reported in poles of this species in North America. There was little radial extension of heartwood infection beyond the advanced decay
An Analysis of Creep-Inducing Stress in Sitka Spruce
Get PDFSmall specimens of Sitka spruce (Picea sitchensis) were placed under a parallel-to-the-grain compressive loading situation in a water-saturated state to examine the adequacy of three-element and four-element spring and dashpot model analogs in describing creep response curves for wood. Stress levels of 10, 20, 40, and 60% of ultimate compressive strength were studied for load durations up to 20 days. Deformation-time measurements were analyzed statistically by means of a computerized, nonlinear, least squares regression analysis and with the aid of graphic analysis.Creep deformation was found to occur at stress levels as low as 10% and at very short time periods. In general, three- or four-element model analogs were adequate to describe time-dependent deformation phenomena for applied purposes; further refinements were deemed superfluous. For time periods of 24 hr or longer, the use of a four-element model is advised, particularly at higher stress levels
An Experimental Study on The Lateral Natural Frequency of Bandsaw Blades
Get PDFTwo solutions for predicting the lateral natural frequency of bandsaw blades are experimentally verified for saw velocity, span length, and tension stress ("strain"). Both solutions are shown to be accurate provided that the effective span length of the guide system, which has been shown for pressure guides to exceed the distance between facing guide edges, is taken into account.It was found that wheel rotation can cause resonance vibration in the backside section of the sawblade, where the blade extending from wheel to wheel is unsupported. This resonance vibration, however, can be avoided by installing a guide midway between the wheels
The Effect Of pH On Decomposition Of Mylone® (Dazomet) And Tridipam To Fungitoxic Methylisothiocyanate In Wood
Get PDFMylone® and tridipam are two solid chemicals that decompose to produce methylisothiocyanate (MIT), a highly effective wood fumigant. In this study, two techniques—a rapid, test-tube method and a small-scale, wood-block assay—were used to determine the effect of the pH of various chemical buffers on the decomposition of Mylone® and tridipam in Douglas-fir heartwood samples colonized by Poria carbonica. Both chemicals were sensitive to pH, and higher levels of MIT were produced as the pH of the buffers increased. In general, fungal survival was not affected I week after chemical treatment. Complete control of P. carbonica, however, resulted after 4 weeks of exposure to 50 mg Mylone®/block or 150 mg tridipam/block, when each chemical was combined with a pH-12 buffer.These results suggest that regulating fumigant treatments according to the degree of fungal attack can substantially improve the precision of decay control in wood maintenance programs
Differentiation of Tracheids in Developing Secondary Xylem of Tsuga Canadensis L. Carr. Changes in Morphology and Cell-Wall Structure
Get PDFThe morphology and the changes in total cell-wall mass in developing secondary xylem of two eastern hemlock trees were studied. Sixty-μm-thick tangential-longitudinal sections were microtomed sequentially from the cambium through the currently developing and the one-year-old increments. The weight and volume of these sequential sections gave data on the rate of mass production. Cross-sectional microtome sections were used to study cell-wall structures and to measure cell-wall layer areas.Four tracheid maturation zones could be measured and described during both early- and latewood formations. The size of the cambium, cell enlargement zone, and the zone of S1 cellulose framework formation were the same throughout the growing season. However, the size of the zone of S2 cellulose formation changed. This zone was only one-third as wide during the formation of the thick S2 layer in latewood tracheids as it was during the formation of the thin S2 layer in earlywood tracheids. Despite the fact that the number of cells produced during S2 layer formation in latewood was only one-third as many as in the earlywood zone, the rate of total mass production was more than twice as great compared to earlywood. Tracheid diameters and cell-wall layer volumes across both the currently developing and the one-year-old xylem showed that size development is complete for each layer before the appearance of the next inner layer in the tracheids. However, cell-wall layer densities continued to increase perhaps well into the second and subsequent growing seasons. Change in the relative proportion of the cell-wall layers across the growth increment was not dominated by the S2 layer. This relative variation of the S2 layer was the smallest of any secondary cell-wall layer across the growth increment. However, it constituted 50-70% of the total cell-wall volume
A Technique for Measuring Fibril Angle Using Polarized Light
Get PDFPolarized-light microscopy has been used to measure the fibril angle of plant cell walls. To do this the polarized light must pass through only a single cell wall of a wood fiber. A simplified method has been developed to produce microscope slides of half-fibers (fibers cut in half longitudinally) by maceration of microtomed wood sections. There are certain important variations from the standard methods in mounting the half-fibers on the slides
Stress-Strain Response of Wood Under Radial Compression. Part I. Test Method and Influences of Cellular Properties
Get PDFA new test system was developed for real-time microscopic observation of wood cell-wall deformation and stress-strain relationship under transverse compression. The system consists of a small compression device, a stereo-microscope, a video microscaler, a videocassette recorder and a computer-based data logger. The significance of this system is that it allows the influence of cellular structure of wood on its stress-strain behavior and the cell-wall collapse mechanism to be studied. This test system was used in a research program aimed at generating some basic understanding of microstructural behavior of wood under transverse compression. Tests were conducted on white spruce specimens to evaluate the proposed test procedure and system, and the influences of some microscopic and macroscopic features such as wood density, cell-wall thickness, and earlywood/latewood ratio. End-matched specimens were tested using the test system at three levels of magnification. Gross and individual ring behaviors were observed and measured by testing at a low magnification (12X). Earlywood and latewood behaviors were measured separately using a medium level of magnification (32X). Finally the mechanism of cell-wall collapse was observed using the highest magnification (160X). Test results show that earlywood and latewood have varying degrees of influence on the various segments of the gross stress-strain curve in radial compression. First collapse of cellular structure occurs at a location with minimum cell-wall thickness and density. Initiation of cell-wall collapse and its gradual progression are clearly visible using the apparatus, thereby verifying the capability of the proposed method
Surface Characteristics of Chemically Modified Newsprint Fibers Determined by Inverse Gas Chromatography
Get PDFThe surface characteristics of treated waste newsprint fibers were investigated using inverse gas chromatography (IGC). The surfaces of waste newsprint fibers were modified with γ-aminopropyltrie-thoxysilane, dichlorodiethylsilane (DCS), phthalic anhydride (PA), and maleated polypropylene. The effectiveness of these surface treatments was monitored by the IGC adsorption curves using n-alkanes and acid-base probes. The empirical acid (KA) and base (KD) characteristics (i.e., electron donor/ acceptor abilities) of untreated and treated newsprint fibers were determined using Schultz's method and were correlated with the surface chemical compositions determined from X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results indicated that the surface of untreated newsprint fibers had an acidic characteristic due to the electron acceptor character of the hydroxyl protons. The newsprint fibers reacted with phthalic anhydride or malcated polypropylene also exhibited an acidic surface behavior attributed to pendent carboxylic groups. Dichlorodiethylsilane produced a strong acidic surface attributed to the highly electronegative nature of the chlorine atoms of dichlorodiethylsilane. However, when the fibers were reacted with γ-aminopropyltriethoxysilane, the basic characteristic (electron donor ability) of the fiber surface was increased, presumably by the presence of attached amino groups