Wood and Fiber Science (E-Journal)
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Small Angle X-Ray Scattering Study of The Porosity in Charcoals
Get PDFSmall angle X-ray scattering data have been obtained for a series of charcoal samples produced by heating in a laboratory furnace under conditions chosen to simulate those encountered in commercial kilns. The scattering curves suggest that the samples contain three types of pores: (1) relatively large pores, with dimensions of the order of a few microns, which are similar to the pores in the lignincellulosic skeleton of the wood from which the charcoal was made; (2) platelet-like pores, with one dimension that does not exceed 2 or 3 nm and with the other two average dimensions being considerably larger; and (3) small pores, which have no dimensions greater than about 1 or 2 nm. For charcoals heated to 400 C, only the large pores are present in appreciable numbers. As the maximum heating temperature is increased, the platelet and small pores make an increasing contribution to the scattering. Estimates have been made of the fraction of the volume of the porous charcoal occupied by each of the three types of pores
Variations in Ultrasonic Wave Velocity and Dynamic Young's Modulus with Moisture Content for Taiwania Plantation Lumber
Get PDFThe effects of moisture content (MC) on the ultrasonic wave velocity, dynamic Young's modulus (DMOE), and the mobility of free water during desorption from a water-saturated condition were examined for the longitudinal, radial, and tangential directions of Taiwania (Taiwania cryptomerioides Hayta) plantation lumber. The ultrasonic wave velocity in the longitudinal and radial direction tended to increase with decrease in MC, and the effect of MC on the ultrasonic wave velocity of Taiwania lumber below the fiber saturation point (FSP) was stronger than above the FSP. Above the MC of 70%, the ultrasonic wave velocity in the tangential direction tended to decrease with decreasing MC, whereas below the MC of 70%, the ultrasonic wave velocity tended to increase with decreasing MC.The DMOE curve also showed a significant change around the FSP in a two-stage relationship with MC values. Above the FSP, DMOE values tended to decrease rapidly with decreasing MC, whereas below the FSP, the DMOE values tended to increase gradually with decreasing MC. The k values for the ultrasonic wave propagated through the longitudinal, radial, and tangential direction of Taiwania plantation lumber were equivalent to 0.58, 0.33, and 0.01, respectively. Using the effective density and ultrasonic wave velocity to calculate the longitudinal, radial, and tangential DMOE, it was found that the DMOE tended to remain constant with MC during the MC reducing process from a water-saturated condition to FSP
Fast Atom Bombardment Mass Spectrometry of Condensed Tannin Sulfonate Derivatives
Get PDFCondensed tannin sulfonate derivatives were studied by fast atom bombardment mass spectrometry (FAB-MS) to assess the feasibility of using this technique for determining molecular weight and structural information about these compounds. Both positive- and negative-ion spectra provided useful data with regard to molecular weight, cation species present, and presence of the sulfonate moiety. Additional structural information was provided in the spectra of the dimer sulfonates by fragment ions resulting from retro-Diels Alder fission and cleavage of the interflavanoid bond. Overall, negative-ion spectra proved to be superior to positive-ion spectra because of less interference from matrix ions. FAB-MS holds promise as a technique for analyzing condensed tannin sulfonates yet to be isolated and will help facilitate development of new adhesives made with these compounds
A Method for Predicting Non-Shear Compliances in the RT Plane of Wood
Get PDFEquations were obtained relating the non-shear compliances in the radial-tangential, RT, plane to each other for a variety of hardwood and softwood species that were at 10 to 12% moisture content. From loadings made on short columns in the tangential, T, direction SRT = -0.255STT + 0.659 x 10-6; for loadings made on columns in the radial, R, direction STR = -0.887SRR - 1.260 x 10-6. In the compliance term Sij, "i" signifies the direction of the observed strain and "j" the direction of the applied stress; i.e., SRT relates strain in the R direction to stress in the T direction. Since SRT = STR for orthotropic materials, it follows that SRR = 0.291STT - 2.188 x 10-6. SRR and STT are entered as negative quantities in the above equations to indicate compression. Units for strain are inches per inch and for stress are pounds per square inch. These equations should be useful for finite element studies in mechanics and for studies on strains developed during wood drying
Multiphase Materials With Lignin. VI. Effect of Cellulose Derivative Structure on Blend Morphology with Lignin
Get PDFPolymeric blends of lignin with ethyl cellulose (EC) and cellulose acetate/butyrate (CAB) were prepared by solution casting from dioxane. Fracture surface analysis by scanning electron microscopy revealed phase separation when the lignin content exceeded 10% for blends with EC and 5% in the CAB system. While this phase behavior is as predicted for the EC blends, a greater level of compatibility had been expected for the CAB blend system. Results from both differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) suggest that the observed phase separation may be a consequence of supermolecular structure development rather than immiscibility. In the case of the EC/lignin blends, the observed Tg of lignin was 25 C and 35 C higher than that of the pure component for the 40 and 50 wt.% blend, respectively; and CAB/lignin blends produced conflicting results by DSC and DMTA. Where DSC revealed single Tg's for all blends with up to approximately 20% lignin, and dual transitions for all other compositions, DMTA data reflected single relaxations with variable Tg's throughout. This discrepancy is tentatively explained through the formation of liquid crystal mesophases in the cellulose derivative/lignin blends during solvent evaporation
Relationships Between Intra-Ring Variables in Mature Douglas-Fir Trees From Provenance Plantations
Get PDFRelationships among a variety of densitometric characteristics of juvenile and mature wood from 360 trees growing in two plantations of a 1912 Douglas-fir [Pseudotsuga menziesii (Mirb) Franco] Heredity Study were examined. Variables included earlywood density (EWD) and width (EWW); latewood density (LWD), width (LWW), and proportion (LWP); average ring density (RD); and total ring width (RW). The RD components (EWD and LWD) had strong phenotypic and genetic correlations with their respective RW components (EWW and LWW). However, no phenotypic correlation existed between average RD and total RW, and genotypic correlation was weak. The relationship between wood density and radial growth varied by plantation and genotype. The potential exists for improving wood density in juvenile and mature wood by selection, with only a minor impact on radial growth. Selection during the juvenile period to improve mature wood quality is feasible for RD, EWD, LWW, and LWP. Further, selection to improve juvenile RW does not result in reduced wood dens ty during maturity
Grid-Based Tactile Sensor System for Shrinkage Pressure Measurement
Get PDFA study was conducted to determine the applicability of a grid-based tactile pressure sensor system in monitoring the shrinkage pressure in wood during drying. The sensor was attached to green red oak (Quercus sp.) and loblolly pine (Pinus taeda L.) boards through a mortise fitted with a two-piece metal insert. As current sensor models could not withstand actual kiln-drying temperatures, the boards were allowed to dry under room conditions (70°F and 60% RH).Results indicate that the pressure sensor system could accurately monitor the shrinkage pressure within the sample boards. Frame-by-frame recordings of the pressure profile across the loaded sensor grids showed not only a visual manifestation of the stress development and reversal phenomena in drying, but also the magnitudes of the internal compressive stresses. For the first time, both real-time visual graphics and quantitative data on compressive drying stresses in wood are made available. The current sensor system is designed exclusively for measuring compressive stresses, and is incapable of monitoring the magnitude of the internal tensile stresses that occur simultaneously with the compressive stresses
Approaches to, and Perceived Benefits of, Training in the Secondary Wood Industry
Get PDFPractitioners and researchers alike have noted that a well-trained workforce is an important component of the competitiveness of U.S. manufacturers in the global economy. This study compares four secondary wood industry sectors on their approaches to, and perceived benefits of, training production employees. The study was based on an Internet survey in the autumn of 2003 of subscribers to a major wood industry publication. A sample of 197 firms was split into four type categories (cabinets, household furniture, contract furniture, and millwork) and two size categories (fewer than 50 employees and 50 or more employees) and compared on several questions related to training of production employees. Some differences were found among the firm types and between the firm sizes. However, the firms were similar in a number of respects. The majority indicated that the return on training was positive, and firms agreed on average that training was critical to their future competitiveness. Implications for domestic competitiveness are noted based on the findings
A New Model to Predict the Load-Slip Relationship of Bolted Connections in Timber
Get PDFThe development of a new approach to predicting the load-displacement interaction of bolted wood connections is described.The European Yield Theory for bolted wood connections has gained wide acceptance in recent years attributed to its closed form, simplicity, and accuracy. But the model does not relate capacity or any other loading state to joint slip. A method to determine deflection related properties of bolted joints in timber with a single equation would be an important contribution to the field of timber engineering. The model would simplify the analysis of large structures including schools, gymnasiums, bridges, and light-industrial buildings where wood could be utilized because of its economy, high-strength-to-weight and stiffness-to-weight ratios.Based on yield characteristics predicted by the European Yield Theory, the joint was abstracted where the dowel rotates about the plastic hinge under a warped force-deformation plane. Through subsequent simple integration along the dowel length, a closed form solution could be developed. The analysis of a two-member connection assembled with a single bolt indicated that the model closely predicts the load-displacement relationship
A Perceptional Comparison of Wood in Separate Infrastructure Markets
Get PDFPerceptions of wood as an infrastructure material were investigated within four distinct market segments and within five geographic regions of the United States. Wood was compared to steel, reinforced and prestressed concrete, aluminum, and plastic on six predetermined factor groups and by thirty material attributes. The foremost factors in material choice decisions were durability, maintenance, and cost. All infrastructure groups rated wood lower in overall material performance as compared to prestressed and reinforced concrete, steel, and aluminum. Only plastic was rated lower than wood in perceived material performance