Wood and Fiber Science (E-Journal)
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Water States in Yellow Poplar During Drying Studied by Time-Domain Nuclear Magnetic Resonance
Get PDFThe time-domain nuclear magnetic resonance (NMR) technique can easily distinguish water states according to spin-spin relaxation time and can give more quantitative information on water in wood than any other method. In this study, water states in yellow poplar were investigated with a time-domain NMR technique. Water migration during drying was also analyzed. The results of this study show that yellow poplar has five components in water states (bound and free water) according to spin-spin relaxation time at moisture contents greater than 100%. The number of different water states decreased with decreasing moisture content. The longest spin-spin relaxation time was about 400 ms for free water, and the shortest was about 1 ms for bound water. With the NMR resonance technique, water states in yellow poplar drying are distinguished easily and migration from one water state to another can be analyzed quantitatively. This technique can benefit wood drying modeling and simulation
Using Benzylated Poplar as Adhesive in Manufacturing Wood-Based Panels
No full textBenzylated poplar was prepared and its properties were characterized by Fourier transform infrared spectroscopy, a soften point test, and differential scanning calorimetry. This study reports on the enhanced thermoplasticity of benzylated poplar with its weight gain increased. Because of its thermoplasticity, benzylated poplar can be used instead of traditional adhesives to coat wood-based panels. Plywood fabricated with benzylated poplar had a bonding strength of 1.84 MPa and an average wood failure of 76.2%. Fiberboard containing 40% benzylated poplar had an internal bonding strength of 0.81 MPa, a modulus of rupture (MOR) of 45 MPa, a modulus of elasticity of 4900 MPa, and a density between 700 and 800 kg/m-3. Wheatstraw board containing 20% benzylated poplar had an internal bonding strength of 0.48 MPa, an MOR of 32 MPa, and a density between 0.5 and 0.6 g/cm-3
Effect of Specimen Width on Shear Modulus of Wood Obtained by Flexural Vibration Tests
Get PDFThis study proposes a method of determining specimen width to increase the precision of shear modulus with flexural vibration. Free-free flexural vibration tests and modal analyses were conducted on Sitka spruce (Picea sitchensis Carr.) specimens 5-150 mm wide, 10 mm thick, and 300 mm long. The specific shear modulus obtained by Goens-Heamon regression based on the Timoshenko theory of bending varied for a large width. Specimen width to clearly identify resonance frequencies of flexural vibration could be obtained by modal analysis. An equation was also developed to easily determine such specimen width
Degradation of Wood Flour/Poly (Lactic Acid) Composites Reinforced by Coupling Agents and Organo-Montmorillonite in a Compost Test
Get PDFTo investigate the degradation properties of wood flour (WF)/poly (lactic acid) (PLA) composites modified with organo-montmorillonite (OMMT) and two types of coupling agents, namely, maleic anhydride grafted polypropylene (MAPP) and silane (γ-methacryloxypropyltrimethoxysilane, KH-570), pure PLA, OMMT/PLA, and WF/PLA composites were prepared with the hot-press molding method and tested in a compost test for 6 mo. After compost tests, samples were also characterized with scanning electron microscopy, Fourier transform infrared spectrum, and differential scanning calorimeter for further understanding. The results showed that 1) introducing WF and OMMT accelerated the degradability of PLA (after 5 mo, all composites were completely degraded, whereas the pure PLA control still had 4.78% residue); 2) the two types of coupling agents had opposite effects on degradation of WF/PLA composites (MAPP delayed the degradation process, whereas silane accelerated it); 3) silane and OMMT had a synergic effect on degradability, which was supported by the complete degradation of WF/PLA composites modified with both silane and OMMT in 4 mo; 4) after a 3-mo compost, many cracks or voids occurred on the surface of PLA, and this compost test also resulted in separated WF. Tm values of PLA and OMMT/PLA decreased and their crystallinity degrees increased, suggesting faster degradation of PLA with WF and OMMT loading
State of the Art Paper: Biomimetics: Adapting Performance and Function of Natural Materials for Biobased Composites
No full textNatural materials may serve as an excellent template for the design of high-performance manufactured materials. Because natural materials are fabricated at standard temperature and pressure from benign chemicals, adapting or mimicking nature's design methods and structures offers the potential to enhance performance, lower energy requirements, decrease toxic chemical accumulation, and create materials with life cycles that better correspond with the environment. As the forest products industry has matured, adapting naturally occurring designs has meant potential innovation for commodity markets, decreasing manufacturing inputs (energy, carbon, or other materials), and enhancing product performance. This study reviews nature-inspired pathways for biocomposites to 1) enhance the specific mechanical properties, 2) assemble materials from aqueous systems, 3) create hybrid inorganic-biopolymer composites, and 4) develop functional hydrophobic coatings and photonic colored films. To achieve controlled architectures found in natural materials, innovative production technologies that allow for timed processes and self-assembly must be applied to biobased composite manufacturing
Characterization of Knots in Plantation White Spruce
No full textKnot size and distribution are of key importance to wood quality and lumber grade yield. This study characterized white spruce (Picea glauca [Moench] Voss) knots with computerized tomography images and knot mapping software. The characteristics included shape, number, diameter, inclination (angle between z-axis and the line connecting the knot's starting point at the pith with the end point), azimuth direction, and distribution inside the stem. There were on average 112 grade-important knots per tree in a 32-yr-old plantation white spruce tree, 7% of which could downgrade lumber from Select Structural to No. 2 and lower grades. A total of 3.6% were ramicorn knots, and 70% had an inclination angle between 60 and 80° with the tree axis. There were 24 more knots per tree with every 2-cm increase in tree diameter. Knot diameters had a positively skewed frequency distribution with an average of 156 mm. The majority of the knots had a taper between 0.18 and 0.38 mm/mm, which could have had a major impact on lumber mechanical properties. Knots grew steeply upward until reaching their greatest diameters and became more horizontal afterward. Butt logs had smaller but a higher number of knots and a lower percentage of knot volume (out of log volume) than those higher up. In the same height growth unit, inclination angle decreased with increasing height. Wider knots had a smaller inclination angle. White spruce has a weak self-pruning mechanism and is prone to forking or ramicorn branching. The widest knot in a height growth unit is more likely to be found in the south direction. Trees from wider spacing tend to have wider knots but not necessarily a higher number of knots at the same heights. The results suggest the need for pruning operations and including knot information in determining sawing strategies. Information from this study should be useful in forest management decision-making and improving wood use
Effect of Temperature on Acoustic Evaluation of Standing Trees and Logs: Part 2: Field Investigation
No full textThe objectives of this study were to investigate the effect of seasonal temperature changes on acoustic velocity measured on standing trees and green logs and to develop models for compensating temperature differences because acoustic measurements are performed in different climates and seasons. Field testing was conducted on 20 red pine (Pinus resinosa) trees and 10 freshly cut red pine logs at a 45-yr-old plantation stand in Arena, WI. Acoustic velocities of the red pine trees and logs and the ambient temperatures were monitored for 12 consecutive months. Results indicated that ambient temperature had a significant effect on acoustic velocities of trees and logs in winter when temperatures were below the freezing point. Acoustic velocities increased dramatically as ambient temperature dropped to below 0°C, but the increase became less significant when the temperature decreased to below -2.5°C. Above the freezing point, acoustic velocities were less sensitive to ambient temperature changes. From a practical standpoint, acoustic velocities of trees and logs measured at different climates and seasons can be adjusted to a standard temperature if measurements are conducted well above or well below freezing temperatures. However, measurements conducted around freezing temperatures could cause complications in making temperature adjustments. Users should avoid conducting field acoustic testing when wood temperature is around the freezing point
Systematic Resource Characterization Through Veneering and Nondestructive Testing
No full textIn this study, a systematic approach was established for resource characterization via veneering and nondestructive testing. A recent study with short-rotation western hemlock (Tsuga heterophylla [Raf.] Sarg) and amabilis fir (Abies amabilis [Dougl.] Forbes) in British Columbia, Canada, was showcased to demonstrate the effectiveness of this approach. By proper tree sampling, veneer processing, and nondestructive testing on a sheet basis, the proposed approach helps rapidly address several critical issues on resource characterization and utilization, such as 1) the impact of stand characteristics on wood properties including density and modulus of elasticity (MOE) or attributes such as wood moisture content and color; 2) the within-tree and between-tree variations of these wood properties or attributes; 3) the spatial distribution of log defects, such as knots and decay; 4) the effect of tree growth rate, stem position, juvenile and mature wood, sapwood, and heartwood on key veneer properties such as thickness, surface roughness, density and MOE; and 5) veneer yield, visual grade, stress grade, and high-value product potentials. To maximize the value return from the available resource, this approach involves an assessment for product options with predicted grade outturns
A Rapid Method to Assess Viscoelastic and Mechanosorptive Creep in Wood
Get PDFThis study presents an alternative method to measure the viscoelastic and mechanosorptive creep of wood using a dynamic mechanical analyzer (DMA). Measurements were made on sugar maple wood specimens in the radial and tangential directions in different RH conditions. Viscoelastic creep measurements showed that DMA can detect effects of time, RH, load level, and wood direction on wood creep. With the applied stress levels (5, 25, 35, and 45%), wood exhibited linear viscoelastic behavior. DMA also demonstrated its value in measuring mechanosorptive effect. The mechanosorptive effect was observed as RH changed during the loading period, resulting in very high deflections. In both viscoelastic and mechanosorptive creep measurements, creep proved to be greater in the tangential direction than in the radial direction. The results of this study demonstrated that a DMA can be a rapid and accurate tool to predict the time-dependent behavior of wood under load
Microscopic Study of Waterlogged Archeological Wood Found in Southwestern China and Method of Conservation Treatment
Get PDFThousands of waterlogged wood pillars beneath crop fields were discovered during the 2008 excavation of an archeological site in southwestern China. Specimens were studied with scanning and transmission electron microscopes, and 2.5 cm x 2.5 cm x 5-cm specimens were dehydrated with methanol followed by treatment with neutral phenol-formaldehyde (PF) resin. The wood, identified as Pinus kesiya var. langbianensis, was severely degraded by bacterial surface erosion and tunneling of cell walls. Bacterial tunneling was more frequently observed near the cell corners with thick walls. Bacterial degradation of cell walls was accompanied by accumulation of degradation products and bacterial slime in cell lumens. Neither brown-rot nor soft-rot decay was detected in the wood. The wood samples gradually darkened after sampling, but removal of degradation products with methanol and a brief 2% oxalic acid treatment reversed the discoloration. The average specific gravity and crushing strength of the waterlogged wood were 0.25 and 7.1 MPa compared with 0.37 and 33.7 MPa of normal wood of the same species. Treatment of the waterlogged wood with neutral PF resin increased specific gravity to 0.44 and crushing strength to 12.8 MPa. The PF treatment minimized shrinkage and stabilized wood color of the waterlogged wood