The research performed exhaustive experiments to help better understand how subterranean termite colonies function in their biodegradation activity in wooden structural elements. Specifically, the research had as main objectives to analyse the usefulness of CO2 as a bioindicator of the presence of termites and their wood biodegradation activity. The obtained results have demonstrated that CO2 emissions of termite colonies vary depending on their wood degradation activity. So, the amount of CO2 emitted is closely linked to the population size and activity levels. The obtained relationship between the CO2 concentration and time for different population sizes can predict termite biodegradation severity and help establish predictive models for pest monitoring in wood structures.
Compression wood is an ideal model for exploring the molecular mechanism of wood formation. To supplement the proteome data in compression wood formation, two-dimensional difference gel electrophoresis (2D-DIGE) proteome technology was used to investigate the protein response to bending the stem of Pinus koraiensis seedlings. The results showed that most of the proteins in wood-formation tissues were distributed in pH from 4-8 and the molecular weight was around 30-97 KDa. In total 24 identified proteins were mainly functional on amino acid metabolism, cell wall synthesis, secondary metabolism, and stress response. Proteins related to methionine pathway and lignin biosynthesis were up-regulated in the formation of the compression wood. On the contrary, lipid metabolism-related proteins were down-regulated during the formation of the compression wood. In additional, some proteins involved in energy metabolism and photosystem were also changed in the tissues during the formation of the compression wood. These findings suggested that 2D-DIGE was a feasible and timesaving technology in proteome analysis of wood-forming tissue. Moreover, proteins were not involved in lignin synthesis pathways, but other metabolites were changed as a response to stem bent treatment. The identified proteins in compression wood formation insight to further investigating the molecular mechanism of wood cell wall biosynthesis.
In this study, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fouriertransform infrared spectroscopy (FT-IR) methods were used to study the structure and the thermal degradation of the cellulose modified with silver nitrate, silver sulphate and silver borate. The absorption of the nitrate derivative is more intense followed by the borate. All the cellulose derivatives showed two degradation steps, except for bromate derivatives which indicated the third peak that is related to a nature and chemistry of a derivative presence. The modification seems competent for an application for modified fillers in polymer composites.
Samples were vacuum-pressure treated with nano-SiO2 water solutions with BET specific surface area of 60,150, 200, 380 respectively, and then impregnated with copper azole (CuAz) preservatives or emulsified wax modified CuAz preservatives. The effects of emulsified wax and nano-SiO2 on the dimensional stability were investigated according to standard GB/T 1934 (2009) after one year outdoor exposure test. The results showed that the addition of nano-SiO2 or/and emulsified wax could reduce the water absorption rate of treated wood, and the best water repellent was observed in the samples treated with BET specific surface area of 60 m2.g-1. The addition of wax into nano-SiO2 modified wood was essential to improve the radial and tangential swelling and shrinkage stability of nano-SiO2 treated wood. The bigger BET specific surface area of nano-SiO2 would be adversely affected the dimensional stability of the treated wood.
In this study, the changes of the individual constituents of wood, mainly lignin fraction, and carbohydrate fraction of partially delignified wood chips were investigated. The concentration of alkali during kraft cooking of spruce chips were characterized with respect to the time of kraft cooking, consumed alkali and also to the time-temperature variable (H-factor). The observation brought a new fact, that the extraction of lignin and degradation of the carbohydrate fraction as well as the wood residue itself, were realized in two different reaction phases: initial and residual. The power form dependences between the studied constituents of the wood during kraft cooking were interpreted in a logarithmic coordinate system by the straight line relationship.
This study was designed to investigate some surface characteristics such as gloss, color, and surface hardness changes of Scots pine wood preimpregnated with some copper-based chemicals before varnish coating after accelerated weathering. While Adolit KD-5 (AD-KD 5), Wolmanit CX-8 (WCX-8), and Celcure AC-500 (CAC-500) were used as copper-based impregnation chemicals, water-based varnish (WBV) was used as a coating material. Results showed that surface hardness and gloss values of Scots pine were increased after accelerated weathering. Impregnated and WBV coated Scots pine gave better surface characteristics compared to only WBV coated Scots pine. In impregnation chemicals, while AD-KD 5 showed the most appropriate chemical, in terms of surface hardness and total color changes, CAC-500 was found the most valuable chemical in terms of gloss changes after 1000 h accelerated weathering exposure.
The objective of this study was to investigate odor active compounds of polyvinyl chloride (PVC) laminated medium density fiberboard (MDF) and explore the effect of temperature on total volatile organic compound (TVOC) and odor emissions. A micro thermal extractor was used based on the technology of gas chromatography–mass spectroscopy/olfactometry. The results showed that fruity, sweet, fragrant, and aromatic were the dominant odor impressions of PVC laminated MDF and were primarily concentrated in aromatics. Decoration treatment could effectively prevent the release of some odor compounds from MDF, yet these could add new odor substances. In the test period, the total odor intensity of MDF decreased more rapidly than that of PVC because of the characteristic of exposure. The TVOC from PVC increased when the temperature increased, and the effect was more significant early in the test period. Increasing temperature could accelerate the appearance of some odor active substances. The fastest release of odorant compounds occurred at 40°C. At higher temperature (60°C in this experiment), some substances could be enhanced, causing an increase in TVOC and odor. The temperature contrast between 40°C and 60°C contributed greatly to the release of alkanes, alcohols, esters, and ketones.
The objective of this study was to investigate the basic wood density (ρk) of the silver birch (Betula pendula Roth.) trees in relation to the stand structure. This research was conducted in three stands of different structure and ages, located in the region of the lower part of the Jeseníky Mountains in the Czech Republic. In total, 71 healthy dominant silver birch trees were randomly selected. Two samples (cores) were taken per tree for performing the tree-ring width analysis and ρk determination. We found that the average ρk of the three examined stands ranged from 471.8 to 494.6 kg. m-3. The older trees showed a high variation of the ρk. The age of the tree and stem diameter positively influenced the ρk. Nevertheless, it was noted that the slenderness ratio had a negative influence on the ρk. Overall, the prediction of wood density using stand and tree characteristics, even when the management history records are available, remains a complex hypothesis.
This article describes techniques used to study mixed biomass fiberboards based on the simulation of wood composition, in which high-strength bamboo could serve as wood cellulose, low-density poplar could serve as wood hemicelluloses, and lignin-rich walnut shells could serve as wood lignin. The effects of different material mass ratios on board properties were discussed, and the bonding mechanisms of the mixed binderless composites were analyzed through Fourier transform infrared spectroscopy (FTIR) and environmental scanning electron microscopy (ESEM). Experimental results showed that the simulation could identify bio-fiberboard compositions with good performance.
One-layer bark panels were internally reinforced with two different grid sizes fiberglass mesh sheets (M1 and M2). The thermal conductivity, water absorption, thickness swelling, static bending properties and internal bond strength of these panels were tested. The reinforcement doesn’t affect the thermal conductivity, but the physical and mechanical properties of the panel were improved. The thickness swelling was reduced by 7.43% and 12.93%; the water uptake decreased by 4.93% and 16.32% for the M1 and M2 sheets, respectively. MOR increased from 0.54 MPa to 2.44 and 2.1 MPa, and MOE increased from 0.28 GPa to 0.66 and 0.63 GPa, respectively. The internal bond didn’t change. The findings indicate that it is possible to produce internal reinforced bark panels for insulation materials depending on the characteristics and tensile properties of the reinforcing materials, as well as the adhesion properties and interfacial interaction of the composite materials.
Heat-treatment woods of Betula alnoides were prepared by using vapor as the heat-conducting medium. Effects of heat-treatment time and heat-treatment temperature on equilibrium moisture content, density, pH value, contact angle and bonding performance of Betula alnoides were discussed in this paper. The results indicated that: (1) With the increase of heat-treatment temperature, the equilibrium moisture content, density and pH value of Betula alnoides decreased gradually. (2) With the increase of heat-treatment temperature, the contact angle of Betula alnoides increased from 70.08° to about 100°, resulting in the reduction of bonding strength gradually. Bonding strength of Betula alnoides after heat-treatment was related with the used adhesive. Bonding strength of different adhesives decreased to different extents. The bonding strength of Betula alnoides wood with polyvinyl acetate (PVAC) resin was generally higher than that of melamine-urea-formaldehyde (MUF) resin. The former were 6.35-4.56 MPa, and the latter were 5.60-3.00 MPa. (3) Heat-treatment time influenced equilibrium moisture content, density, contact angle, pH value and bonding strength of Betula alnoides less than heat-treatment temperature. (4) Heat-treatment could affect strength and surface performance of Betula alnoides greatly and the processing medium should be extended.
This study conducted to quantify and compare the variation among root, stem, and branch wood of Acacia salicina and Albizia lebbeck. Results of this study revealed that the proportion of wood elements is quite similar. The wood cells decrease in length and width (diameter) in the acropetal direction. These traits indicate the principles of the hydraulic architecture of a tree as a perfect adaptation for maintaining the pressure gradient. A. lebbeck has the higher hydraulic conductivity and non-lumen fraction value. It indicates that A. lebbeck has a higher photosynthetic capacity and specific gravity. Thereafter, all of the vulnerability indexes are greater than 3, so both of examined species categorise as mesomorphy species. However, in arid circumstance, A. salicina is potentially much stronger to withstand drought-prone than A. lebbeck.
In this paper, the warpage of the Taxodium hybrid ‘zhongshanshan’ veneer was measured by 3D laser scanning technology. The results showed that, the deformation of this veneer was mainly due to the warpage phenomenon along the cross striation of the wood. Air-drying shrinkage clearly enlarged the length in the direction of cross striation compared to the direction of parallel grain. The air-dried veneer would incline 7-12° along the direction of the parallel axis. When peeling the wood of the Taxodium hybrid ‘zhong shan shan’, the diameter decreased, and the warpage degree of veneer increased. The average veneer warpage degree of sapwood was 21.18%, the intermediate wood was 28.20%, and the heartwood near piths was 40.88%. High resolution 3D laser scanning technology accurately, intuitively, and rapidly obtained the deformation of the veneer.
In this paper, an experimental research on bending behaviour of end-notched glulam beams and their bending behaviour after repairing with glass fibre reinforced polymer (GFRP) bars is presented. Altogether five glulam beams (100 x 220 x 4000 mm) made of spruce timber classified in the strength class C22 were tested. Experiment showed that originally, the beams failed in a brittle manner due to crack opening and its propagation. Cracks in the notch details were a result of excessive tensile stresses perpendicular to grain and shear stresses. Repairing the beams with GFRP bars after their failure completely restored and notably improved their load carrying capacity (average increase of 194%). Failure mechanism after repair changed from the original brittle tensile failure to more ductile failure in bending for most beams, proving the successfulness of the intervention. This study gives an insight in rehabilitation and repair possibilities of existing structures using advanced materials like GFRP bars.
This study was carried out to compare to the effects of glass-fiber fabric, which might be a new alternative edge band, to PVC and wood veneer edge bands which is used commonly in today’s furniture in wood-based materials melamine impregnated paper coated medium-density fiberboard and melamine impregnated paper coated particleboard on strength of corner joints. For this purpose, the 0.4 mm wood veneer, 0.4 mm PVC, 4 mm PVC, and fabric edge band were used as the edge bands. It was prepared 13 different configurations. The prepared test samples were subjected to the tension and compression tests. The data from the experiments was evaluated by means of multiple variance analysis. This study showed that the joint with the fabric edge band was 34% and 30% higher than 2 mm PVC band, 26% and 23% 0.4 mm PVC band, 22% and 22% 0.4 mm wood veneer band, and 16% and 23% higher than control (for tension and compression, respectively). In addition to, it is to be understood that the fabric may be used like as commercially available edge bands.
To characterize the delamination process of Ceiba plywood, an energy approach was used. This approach considers that crack propagation is a phenomenon of energy dissipation. The fundamental parameter of this approach is the energy release rate (G). To determine this parameter in pure mode I (GI), a Double Cantilever Beam test (DCB) was deployed. The critical energy release rate in pure mode I (GIC) is determined using four approaches, namely Beam Theory, Berry compliance law, Modified Beam Theory and the Compliance Calibration method. Then, a resistance curve of Ceiba plywood was determined according to each approach. Finally, a fracture surfaces analysis was discussed to understand the nature and types of fracture.