Wood and Fiber Science (E-Journal)
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Evaluation of Moisture Content Changes in Taiwan Red Cypress During Drying Using Ultrasonic and Tap-Tone Testing
Get PDFMoisture content affects most of the important properties of wood, therefore it is important to control during drying and in use. The purpose of this study was to investigate moisture content changes in Taiwan red cypress during drying. Two types of nondestructive testing were used, ultrasonic and tap-tone. The results showed that ultrasonic and tap-tone velocities increased with decreasing moisture content with the major effect below the FSP. A second-order regression relationship was found between ultrasonic and tap-tone velocities with moisture content desorption during drying with a coefficient of determination of 0.77 and 0.88, respectively. Moreover, the effects of moisture content desorption on dynamic moduli, calculated from ultrasonic and tap-tone methods, were demonstrated. Finally, a new parameter (Vi/Vx), the ratio of initial velocity (before drying) to the velocity at any moisture content, was effectively applied to evaluate moisture content changes in wood during drying. The tap-tone method was found to be a reliable tool to measure moisture content changes during the drying of wood
Effect of Vacuum Time, Formulation, and Nanoparticles on Properties of Surface-Densified Wood Products
Get PDFSurface-densified wood products were prepared with only a short vacuum impregnation process instead of the traditional time-consuming pressurizing stage. The top layer of engineered wood flooring planks was successfully impregnated with low-viscosity 1,6 hexanediol dimethacrylate and trimethylolpropane trimethacrylate as well as layered silicate nanoparticles by vacuum impregnation of 30 s to 10 min. Treating tests involved two species, maple and oak, and Brinell surface hardness, impact resistance, and abrasion resistance of the treated wood specimens were measured. Brinell surface hardness increased from 5.05-15.42 MPa for maple, the greatest improvement of 205% being obtained with a 30-s vacuum. For oak, Brinell surface hardness increased from 5.25-11.05 MPa with a 60-s vacuum, an improvement of 108%. Impact resistance was based on measurements of indentation diameters and depths in falling ball tests. Decreases in indentation diameters from 4.96-2.84 mm and indentation depths from 0.172-0.034 mm were observed for maple treated with nanoparticle-containing formulations and a 60-s vacuum impregnation, indicating that impact resistance of a one-step, short vacuum impregnation time dramatically improved wood surface hardness. Measurements of abrasion resistance properties of surface-densified specimens were based on specimen weight loss with time following abrasion tests. Weight loss values decreased considerably with treated wood. A factorial experimental design provided information on effects of vacuum time, nanoparticles, and wood species on properties of impregnated wood specimens. Impacts of individual factors and their interactions were analyzed with Statistical Analysis System
From Hydrophilicity to Hydrophobicity: A Critical Review—Part II: Hydrophobic Conversion
Get PDFThis review consists of two parts. Part I considered the hydrophilic nature and wettability of the surface of wood, including wetting theories, surface tension, surface topography, and surface contamination of wood. Part II focuses on chemical transformation of the surface of wood from hydrophilic to hydrophobic. Literature concerning acetylation, metal oxide treatment, sol-gel process, modification with chlorosilanes, grafting of polymers, microemulsion, layer-by-layer deposition, and plasma treatment are discussed. Conventional methods such as acetylation, metal oxide treatment, sol-gel process, and microemulsion can only reduce and/or delay water and moisture sorption. Recent increasing interest in nanotechnology provides new opportunities and perspectives on hydrophobic transformation of the wood surface
Moisture Content Variation in Kiln-Dried Lumber from Plantations of Vochysia Guatemalensis
Get PDFVochysia guatemalensis is planted across large areas of Latin America; however, a major problem with its use is the large variation in final moisture content (MCf) after drying. This research studied the causes for high moisture content variation. Variables included the climate in which the tree was grown, the amount of heartwood, grain pattern within the piece, sample distance from the pith, and height of the log. The results showed that the initial moisture content (MCi) ranged 110-280% and MCf 10-17%. The variation in MCi was attributed to climatic conditions, heartwood presence, grain pattern, and height of the log. Boards with a radial surface in width produced the highest MCf. The MCf of lumber tended to increase with distance from the pith, and sapwood had lower MCf than heartwood. V. guatemalensis produced wet pockets in 42% of the dried boards
Study of Manufacturing Thermochromic Wood
Get PDFThe development of new materials such as thermochromic wood provides an interesting option for the forest products industry. Poplar veneer was colored by ultrasonic impregnation using a thermochromic agent consisting of thermochromic dye, a chromogenic agent, 1-tetradecanol, and a sensitizing agent. In optimizing the process, the most significant influence on the extent of sample color change (ΔE) was found to be the mixing ratio of thermochromic dye to chromogenic agent. Next was the mixing ratio of thermochromic dye to 1-tetradecanol and last that of thermochromic dye to sensitizing agent. Analysis of 0variance showed that the influences of all experimental parameters on ΔE were significant at the 0.01 level. The optimum mixing ratio of thermochromic dye, the chromogenic agent, 1-tetradecanol, and the sensitizing agent was 1:8:50:1. The color of these new products changed from blue to wood color as temperature increased 26-34°C and reverted from normal wood color to blue as temperature decreased from 34-26°C
Bioenergy Properties of Juvenile Hybrid Poplars and Their Parent Species
Get PDFBioenergy properties of poplar species Populus trichocarpa (PT), Populus deltoides (PD), and their hybrid were evaluated. Hybrid poplar trees from the cross between PT and PD presented different anatomic, physical, chemical, and thermal properties from their parent species. Anatomic results tended to suggest that hybrid poplar, with fewer vessels per unit area, had more resemblance to PT. Extractive content ranged from 10.64-11% for PD, PT, and first-generation hybrid poplar, whereas it varied from 8.8-9.5% for backcross offspring (BC2-BC5). PD had the greatest average lignin content of 25.6% followed by first-generation offspring and backcross offspring with lignin content of approximately 25%. Holocellulose content of hybrid poplar species was higher than that of their parent species. Observed stem/stump proximate results ranged from 72-74.7%, 25-28%, and 0.80-1.7% for volatile matter, fixed carbon, and ash content, respectively. Heating values observed along the stem were slightly higher than at the stump, ranging from 7498-8356 kJ. TGA-FTIR analysis indicated that H2, CO2, CH4, and CO were the dominant gaseous components from wood pyrolysis
Mechanical Properties of Cellulose Nanofibril-Filled Polypropylene Composites
Get PDFCellulose nanofiber (CNF), microfibrillated cellulose (MFC), and microcrystalline cellulose (MCC) filled-polypropylene (PP) composite samples were manufactured using a melt mixing technique. Mechanical testing was conducted to investigate tensile and flexural properties of the composites at different filler loading levels. Test results showed that in the case of cellulose nanofibril fillers, the composites sustained considerable tensile strength up to 10% (w/w) filler loading whereas the tensile strength of the MCC-filled composites decreased continuously. Moreover, tensile modulus increased as filler loading increased for all cellulose fillers. CNF and MCC-filled composites demonstrate plastic deformation and longer elongation at break than MFC-filled composites while MFC-filled composites exhibited a quasi-brittle behavior under tensile deformation. Flexural strength of cellulose nanofibril-filled composites decreased slightly as a function of filler loading up to 6% (w/w) and increased beyond 6% (w/w). The 10% (w/w) cellulose nanofibril-filled composite samples exhibited sustained flexural strength as compared with neat PP. The trend of increased flexural modulus of elasticity behavior was identical to the tensile modulus of elasticity behavior
Change of Temperature and Pressure in Dry and Green Douglas-Fir and Sugi Wood During Passive Impregnation Method
Get PDFThis work investigated pressure and temperature change in green and dry Douglas-fir and sugi wood during passive impregnation treatment with copper azole type B preservative at higher concentration. Temperature and pressure sensors were used in wood for obtaining temperature and pressure change data every 10 s during the preservative treatment. Gross preservative and X-ray fluorescence spectroscopy was used to obtain retention. Penetration was measured following the standard. Although temperature rise was steeper in green Douglas-fir, pressure was higher in green sugi. However, phenomena were similar for dry lumber of both species. Preservative retention was very high (6.63 kg/m3), and in most cases, it exceeded the requirements of permanent structural components in ground contact applications. Preservative penetration was almost 100% for all samples