Wood and Fiber Science (E-Journal)
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VOLATILE ORGANIC COMPOUNDS EMITTED FROM UNTREATED AND THERMALLY MODIFIED WOOD - A REVIEW
Full text linkVolatile organic compounds (VOCs) are a diverse group of compounds that can have a strong impact on indoor air quality.Wood and thermally modified wood emit VOCs, which are referred to as wood VOCs, and can elicit various negative or positive effects in different organisms, including humans. Wood is a complex multicomponent biopolymer with inherent variability, which is also reflected in the emissions of VOCs. Variability in wood VOC emissions has been attributed to endogenous and exogenous factors, such as wood species, type of wood sample, wood treatment, etc. Nevertheless, studies have reported reasonably consistent results regarding VOC emissions from individual (thermally modified) wood species. Softwoods emit the highest concentrations of wood VOCs composed primarily of volatile terpene emissions (70-90%) and lower concentrations of hexanal and acetic acid (10-25%). VOC emissions from hardwoods are considerably lower (approximately 50 times) and include hexanal and pentanal, acetic acid, as well as other VOCs formed during wood degradation processes, but not volatile terpenes. Total VOC emissions from softwoods are reduced following thermal treatment, whereas emissions are increased from hardwoods after thermal treatment. In thermally treated softwoods, emissions of volatile terpenes and hexanal are drastically decreased, whereas those of acetic acid and furfural increase. Similarly, in thermally treated hardwoods, the emissions of hexanal and pentanal are reduced, whereas acetic acid and furfural, as well as other compounds increase. In addition, formaldehyde emissions are ubiquitous, albeit at low concentrations, but increase following heat treatment. Furthermore, the number of VOCs emitted from thermally treated wood increases with heat treatment temperature. This review article will help guide future research, particularly the evaluation of the impact of different wood species on indoor air quality and the development ofmodification techniques that target extraction or suppression of VOCemissions.
Bamboo Metallization for Aesthetic Finishing of Furniture and Wood Decorative Objects by An Electroless/Electrolytic Process
Full text linkThis work aims to propose and describe bamboo metallizing, in part or totally, for furniture or aesthetical decorations. Bamboo provides a diverse metallic appearance; however, its use with real metal, already conferred to plastics, may increase the chance of use of this green material. The furniture industry requires sustainable options for both the base material for manufacturing of many pieces of furniture with a useful purpose, and surfaces finished with high quality and variety in their aesthetic appearance. This includes bamboo ornaments, which are useful to complement interior decoration. The coatings obtained include copper, silver, nickel, brass, and tin, each of which had some variants in luster. The main change incorporated into the process for metallizing nonconducting surfaces was the introduction of a common base for all surfaces, regardless of its roughness, shape, size, or other surface conditions. Then, this base was taken through an electroless process followed by electrolytic stages. Modification of the current process prevents the need for an initial stage of etching to increase chemical conditioning and roughness. The obtained metallic luster was that intended for decorative applications
MOMENT CAPACITY OF FURNITURE CORNER JOINTS MADE FROM BAMBOO-ORIENTED STRAND BOARD
Full text linkAs an alternative to wood, bamboo-oriented strand board (BOSB) demonstrates immense potential for applications in architecture and furniture. In this study, the corner joint performance of its L-type components under different failure modes and joint techniques was analyzed to evaluate the safety and stability of BOSB as structural materials. Results revealed that the component using wooden dowel pins exhibits the highest bending moment capacity, and the joint strength of BOSB is1.5 times greater than that of particleboard (PB), indicating that the BOSB performance meets product applications. Furthermore, the corner joint of the component in the compression failure mode was more likely to fail in comparison with the tensile failure mode, and the ultimate bending moment capacities for BOSB and PB in the tensile mode were 1.5 and 1.7 times those in the compression mode, respectively. Experimental results are thought to contribute to the understanding of a more reasonable structural design
The Current and Future State of Wood Science Education in the United States
Full text linkEleven institutions were asked to participate in a meeting looking at the future of the discipline early in 2018 (Oregon State University, University of Idaho, Mississippi State University, North Carolina State University, Virginia Technology University, Auburn University [AU], University of Minnesota, University of Maine, West Virginia University, Pennsylvania State University, and Michigan Technological University). Efforts were made to invite the department head or a senior representative of each program. All institutions accepted the invitation. Participants were asked to complete a set of questions regarding their individual programs. Each representative then provided a 30-min overview of their programs and the changes/planned changes to occur. Two of the programs involved were new/or being established included AU and Michigan Technological University. Both of these universities previously had wood science programs and are now reestablishing them. It is important to emphasize that of the 11 participating institutions, all are land-grant universities except one. Furthermore, the forest economy is significant to the prosperity of the states represented
A NUMERICAL STUDY OF THE EFFECT OF GREEN-STATE MOISTURE CONTENT ON STRESS DEVELOPMENT IN TIMBER BOARDS DURING DRYING
Full text linkTimber boards manufactured with a traditional sawing pattern often contain both heartwood and sapwood. The difference in moisture content between heartwood (30-60%) and sapwood regions (120-200%) result in a radial moisture variation that can cause internal constraints during drying. However, the green state moisture content is seldom considered when evaluating kiln drying schedules. The developed numerical model is able to simulate stress development in timber boards, which are dried from green state to equilibrium moisture content. The model studied the effect of initial moisture content on stress development in timber boards during drying. The model operates on continuum level and consists of a coupled transient non-linear orthotropic moisture flow analysis, while a stress analysis considers elastic, hygroscopic and mechano-sorptive strain behaviour with use of the finite element method. The simulations were performed on four different timber board configurations, each defined by a unique pith location. The study shows that the green state moisture content does not necessarily lead to significant constraints, but has a positive effect on the maximum tensile stress found in tangential direction at the exchange surfaces in the beginning of the drying process. In this stage, stress development is mainly governed by shrinkage close to the surface, which is partly prevented due to regions still above the fibre saturation point. The initial MC can also influence the time when the maximum stress occurs, but not necessarily the location
Laboratory Immersion Method for Accelerated Prediction of Preservative Leaching from Pressure-Treated Wood Exposed to Precipitation
No full textThis paper reports on the development of accelerated laboratory methods to allow estimation of preservative leaching from pressure-treated wood exposed to precipitation. End-matched lumber specimens were pressure-treated with a boron-copper formulation and exposed to either natural weathering for one year, laboratory immersion protocols, or a laboratory simulated rainfall protocol. The rainfall run-off or immersion water was collected at intervals according to the method used and analyzed for concentrations of copper and boron. Of the laboratory methods evaluated, the simulated rainfall approach resulted in leaching patterns most similar to outdoor exposure, especially in the case of copper. However, this method is relatively complex and not ideally suited for standardized use. Although the immersion methods evaluated initially exaggerated leaching, reasonable approximations of leaching from one year of natural weathering were achieved with accelerated testing. Models were developed to relate hours of immersion to millimeters of precipitation, and used to evaluate how well the immersion methods might predict leaching from natural weathering over many years of exposure. One of the methods produced boron and copper leaching estimates that were within 15% and 7% (respectively) of losses predicted for wood exposed to 5 years of natural weathering. The results indicate that laboratory immersion methods have value in estimating long term preservative leaching from treated wood products exposed to precipitation
IMPROVEMENT SCHEME AND VERIFICATION OF HIGH-FREQUENCY HEATING UNIFORMITY OF WOOD
Full text linkThis study was based on the finite element method to construct a high-frequency heating temperature field simulation model. In the model, the bending length and angle of top plate were changed upwards. The heating uniformity of test material was then analyzed under different conditions (bending length and angle) to identify the best improvement scheme and carry out the experimental verification. The results showed that when the bending length and angle of top plate were 200mm and 45°, the heating uniformity was the best. Comparison of temperature distribution along the width direction of test material before and after improvement, it was concluded that the temperature distribution was more uniform after improvement. Comparison the temperature difference between the center of test material and its length, width and thickness direction measurement point before and after improvement, the temperature difference was reduced by 7.6℃, 1.7℃, 3.4℃, respectively, which effectively improved the heating uniformity. Comparison of the changes in the electromagnetic field distributions between plates before and after improvement revealed an increase in distribution uniformity from 0.631 to 0.811. This indicated that the electromagnetic field distribution after improvement was more uniform with ideal heating effect. Overall, the improvement in bending length and angle of top plate could change the distribution of electromagnetic fields between the plates and enhance temperature distribution uniformity of wood during high-frequency heating
PHYSICAL AND MECHANICAL PROPERTIES OF GLUED-LAMINATED LUMBER FROM FAST-GROWING TREE SPECIES USING MAHOGANY TANNIN ADHESIVE
Full text linkTannin from mahogany bark extract contains polyphenols that could be used in adhesives. In this study, tannin (T) was reacted with resorcinol (R) and formaldehyde (F) at a ratio of 100:3:5 (w/w/w) under alkaline conditions to make an adhesive. The physical–chemical properties of tannin and TRF adhesive were assessed. Three-layer glued–laminated lumber (glulam) made with wood from jabon (Anthocephalus cadamba), pine (Pinus merkusii), and sengon (Falcataria moluccana) was bonded using TRF with a glue spread of 280 g/m2, cold pressed at 1.47 MPa for 4 h, and then clamped for 24 h. Glulam physical–mechanical properties were tested based on Japanese Agricultural Standard (JAS) 234-2007. Comparison of the physical properties of mahogany tannin and TRF showed that the solids content of mahogany tannin increased after becoming TRF. Compared with phenol resorcinol formaldehyde (PRF) resins, TRF had a similar appearance and specific gravity, but differed in solids content, viscosity, and gel time. Matrix-assisted laser desorption/ionization (MALDI)-time of flight mass (TOF) spectra revealed that mahogany tannin could be classified as hydrolyzable, and pyrolysis Gas Chromatograph-Mass Spectroscopy (GC-MS) showed that the phenolic content was 8.87%. Copolymerization in TRF was indicated by a shift in wave number in Fourier transform IR, reduced percentage of the phenolic component, and increased pH and melting temperature. Mahogany tannin could be prepared for cold-set TRF glulam adhesive, and all glulams fulfilled JAS 234-2007 with regard to MC and MOR. Although TRF adhesive contained a small amount of resorcinol, it was suitable for low density wood, and in dry condition performed equal to PRF
Lower Tolerance Limits for Screw Withdrawal in Wood
Full text linkIn this study, the lower tolerance limits (LTLs) for screw withdrawal strength in wood were investigated. For this purpose, specimens were prepared from white oak and red oak wood (22.2 x 63.5 x 305 mm), a material widely used in furniture industry. Screw withdrawal tests were performed from tansverse, radial and tangential sections of wood specimens. Sample sizes for this study were determined by using modified Faulkenberry-Week methods. After considering normality, randomness and homogeneity assumptions for tolerance analysis, LTLs were obtained from data sets in each sample group. According to screw withdrawal tests, ultimate tensile strength was15.04 MPa, 17.93 MPa, and 16.77 MPa for red oak specimens; from each section, respoectively. Likewise, those of white oak specimens were 16.36 MPa, 19.67 MPa, and 17.21 MPa, respectively. Results of LTLs for 0.99/0.99 confidence/proportional level were 8.69 MPa, 11.96 MPa, and 10.30 MPa for red oak specimens, and 9.67 MPa, 11.14 MPa, and 11.58 MPa for white oak specimens from transverse, radial, and tangential sections of wood in screw withdrawal test, respectively. The study provides a systematic procedure to estimate design values for screws joints.