Fungal decomposition of wood severely affects the soundness of timber constructions. The diagnosis of wood decay requires direct observations or sampling by skilled experts. Wood decay often occurs ...in obscure spaces, including the enclosed inner spaces of walls or under the floor. In this study, we examined the ability of machine olfaction to detect odors of fungi grown on common construction softwoods to provide a novel diagnostic method for wood construction soundness. The combination of a simple device equipped with semiconductor gas sensors (gas sensor array) and multivariate analysis discriminated a fungi-related odor from control odor without instrumental analysis (e.g., gas chromatography). This method is often referred to as machine olfaction or electronic nose. We measured the odor of wood test pieces that were infected with
Fomitopsis palustris
or
Trametes versicolor
and sound test pieces using a gas sensor array. The sensor responses of the specimens showed different patterns between the inoculated and control samples. Each specimen class formed independent groups in a principal component score plot, almost regardless of wood species, fungal species, or cultivation period. This method provides a new decay diagnosis method that is cost-effective and easy to operate.
More than 200,000 tons of scallop shells are disposed annually alone in Japan. Nanoparticles derived from scallop shells have the potential to adsorb gaseous formaldehyde; therefore, such discarded ...shells have now been tested as additive filler in plywood adhesive by mixing high specific surface area, urea-modified shell nanoparticles with a resorcinol–formaldehyde resin. With this procedure, it was found that the emission of formaldehyde from the resulting plywood could be substantially reduced. The urea-modified scallop shell nanoparticles were prepared by two different methods: (1) a dry method where the shells were treated by planetary ball-grinding under ambient conditions—a completely dried powder was obtained after addition of the surface-modifying urea solution; (2) a moist method by treating dry ground shell particles in a wet grinding process with the urea solution, followed by centrifugation to obtain a paste. The specific surface area of the nanoparticles obtained by both treatments was 42 ± 3 m
2
/g. Measurement of the subsequent formaldehyde emission showed that the addition of the modified scallop shell nanoparticles substantially reduced the formaldehyde emission from plywood. The reduction of the specific mass uptake of urea depends on the nanoparticles which especially was the case when resins containing nanoparticles processed by the moist method were used.
Graphene oxide (GO) has theoretically been identified as a candidate for adsorbing formaldehyde molecules. However, whether GO can actually serve as a scavenger for formaldehyde resin adhesives must ...be experimentally verified due to the complex interaction between GO and formaldehyde molecules in the presence of resin, the competition between the formaldehyde emission rate and its adsorption rate on the scavenger, and other complications. From the results from this study we experimentally demonstrate that GO synthesised by the improved Hummers' method is a powerful scavenger for a urea-formaldehyde (UF) resin. We investigate the effect of the added amount of GO on the formaldehyde emission from UF resin. The emission from the UF/GO composite resin is 0.22 ± 0.03 mg L
−1
, which is an 81.5% reduction compared to that of the control UF resin when adding 0.20 wt% GO into the UF resin. However, adding higher amounts of GO (more than 0.20 wt%) increases the formaldehyde emission and the emission approaches that of pure UF resin (1.19 ± 0.36 mg L
−1
). This is likely due to the more acidic pH of the composite, which may lead to a faster curing reaction of the UF resin and acceleration of the emission.
This is the first experiment to demonstrate that GO effectively prevents formaldehyde emission from UF resin.
The effect of addition of
Acacia mangium
bark powder on the thermosetting processes of two commercial phenol resins, PF-A and PF-B, was examined by bond strength test, torsional braid analysis, and ...differential scanning calorimetry. When the bark powder was added to PF-A, the bond strength of plywood pressed at 110°C increased and was comparable to that of plywood pressed at 120 and 130°C. However, when the bark powder was added to PF-B, the bond strength of plywood pressed at 110°C was still lower than that of plywood pressed at 120 and 130°C. The relative rigidity and loss tangent of PF-A cured with the bark powder obtained by heating at 100°C were comparable to those at 120 and 140°C, and the reaction enthalpy was increased by bark powder addition. In contrast, chemical reactions for cured PF-B were not enhanced by bark powder addition.
We evaluated the adhesive properties of plywood used as floor sheathing (Concrete form plywood, tropical wood, 12mm thickness, type 1 according to Japanese Agricultural Standard for plywood) ...extracted from nine houses in Hokkaido. Furthermore, we examined adhesive properties of new control plywood after accelerated aging treatments, and we compared its deterioration with the effects of actual use. In the accelerated aging tests by cyclic boiling, shear strength and wood failure decreased as the number of boiling cycles increased. Before this treatment, a clear positive correlation was observed between the density and the shear strength of the control plywood; however, the correlation was diminished due to the treatments. That is to say, high-density plywood tended to be more deteriorated than low-density plywood. The retention of shear strength of the used plywood, which was estimated on the basis of the shear strength of the new control plywood, decreased as the density of the plywood increased. This tendency agreed with the results of the accelerated aging tests of the control plywood. These results showed a practical possibility of durability assessments of structural plywood by converting the number of boiling cycles in the accelerated aging tests into equivalent periods of actual use.
Fire retardant-treated (FRT) wood with a series of phosphoric acid and amino resin (leach-resistant type) or a mixture of phosphoric acid and boric acid (indoor use type) was weathered for up to 10 ...years at three places in Japan. Test results showed that FRT wood with a series of phosphoric acid and amino resin had high chemical retention and fire retardancy after 10 years compared with FRT wood with a mixture of phosphoric acid and boric acid. From 5 to 10 years, Decrease in fire retardancy of uncoated FRT wood treated with each fire-retardant was slower than up to 5 years. Fire retardancy of FRT woods with each fire retardant after 10 years, increased by coating with combination of fluorine resin-based and polybutadiene-based paint. FRT wood with a series of phosphoric acid and amino resin might keep initial fire retardancy for 10 years, if coated with the above paint. For uncoated and coated FRT wood with a mixture of phosphoric acid and boric acid, it showed that fire retardancy after 10 years was influenced by weathering sites. The condition for setting up the weathering rack was considered the reason for the influence of the weathering site on fire retardancy of weathered FRT wood.
In order to document the outdoor exposure performance of glued laminated timber, decay and shear strength of structural curved glued laminated timber used for 30 years as the elements of a symbol ...tower were determined. Decay was observed at the bottom parts of the glued laminated timber, but not at the top and middle parts. Solid wood and adhesively bonded block-shear specimens were obtained from all parts except the decayed area. The shear strength of the adhesive layer and wood were lower at the bottom than the top and middle parts. There was a positive correlation between shear strength of the wood and the density, but no correlation was found between that of the adhesive layer and the density. Also, the shear strength of the adhesive layer was lower than that of the wood. The shear strength of the wood did not differ between the side and center parts in the width direction near the central layer, while the adhesive shear strength at the side part was lower than that of the center part. At the side part of the glued laminated timber, the adhesive shear strength decreased because stresses developed near the adhesive layer when the wood swelled and shrunk due to wetting and drying.
The aim of this study was to examine the effect of the radial location of veneer on the strength properties of laminated veneer lumber (LVL) in Japanese larch grown in Hokkaido. We manufactured LVL ...using veneers taken from different radial locations in logs, and then examined their strength properties using bending and horizontal shear tests. In addition, we examined how annual ring width of the logs influences the modulus of elasticity of both the logs and the veneers. Our results suggested that there was a significant negative correlation (p < 0.01) between the average annual ring width and the modulus of elasticity of the logs. The modulus of elasticity of veneers (EV) increased as distance from the center of the veneer lathe spindle increased, and average EV was higher for logs with lower average annual ring width. In addition, we compared the strength properties of LVL composed of veneers sourced from the outer part of logs (>12 cm from the center of the veneer lathe spindle) with that sourced from the inner part of logs (<10 cm from the center of the veneer lathe spindle). LVL composed of the outer veneers was stronger than that composed of the inner veneers; 53% higher in modulus of elasticity, 65% higher in bending strength, and 26% higher in nominal shear strength. These results indicate that veneer sorting by radial location in logs is effective.
Functional plywood can produce constant heat by applying a voltage to the conductive bonding layer between wood sheets. Herein functional plywood was prepared by filling various microsized graphite ...particles (3.3-52.5μm in diameter) and nanosized carbon black (CB ; 29 nm) into a phenolic resin. To investigate the electrical conductivity, the resulting composite resin was coated onto a commercial glass slide. The effects of particle size, mass fraction of the conductive fillers (graphite and CB), and the weight ratio of graphite to the fillers (φ = graphite / (graphite + CB)) on the conductive properties of the composite resin, particularly the specific resistance and its variation coefficient, were estimated. A composite resin, which included at least 30 mass% of filler, yielded a relatively low variation coefficient for the specific resistance. Additionally, the composition of the resin had superior conductivity when the weight ratio was 55-66 mass% and the graphite particles were 22.9μm or less in diameter. The above experiment indicated heating plywood was produced. Consequently, its surface temperature was measured. With respect to particle size, the standard deviation in the surface temperature of the plywood corresponded to that of the conductive properties on the glass slide. Hence, the method proposed herein using a glass slide is suitable for conductive characterization to determine the appropriate conditions to prepare heating plywood.
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