Resistance Of Wood Research Articles

Resistance of wood coated with oriental lacquer (urushi) against damage caused by subterranean termite

The sap of urushi tree (Toxicodendron vernicifluum (Stokes) F.A. Barkley) has been used for coating materials and is known as urushi or oriental lacquer in East Asia. The potential of termite attacks against wood samples coated with four types of urushi: Ki-urushi, Sugurome-urushi, Kuro-Sugurome-urushi, and Bengara-urushi, in correlation with their chemical and mechanical properties was investigated in this study. Mortalities of the subterranean Formosan termite (Coptotermes formosanus Shiraki) after a 3-week no-choice feeding tests in samples coated with all types of urushi showed no significant difference from those of control samples. However, mass loss of the sample coated with urushi was lower than that of the control sample especially for Sugurome-urushi (Tukey’s test: p < 0.05). Results of Fourier transform infrared spectra analysis suggested that the degree of crosslinking reaction of Sugurome-urushi was higher than that of other urushi. The highest indentation stiffness was detected in the sample surface coated with Sugurome-urushi and Sugurome-urushi film, which have better ductile properties when compared with others. Moreover, the tangential section of Sugurome-urushi was smoother than that of the others. Increasing the hardness and smoothness of wood samples by coating with urushi could be effective in preventing termite penetration.

Analysis of the mechanical properties of wood attacked by Xylotrechus arvicola (Coleoptera: Cerambycidae) larvae, and its influence on the structural properties of the plant

Xylotrechus arvicola is an invasive insect on Vitis vinifera in the main wine-producing regions of the Iberian Peninsula. X. arvicola larvae bore into the grapevine wood and make galleries, which cause structural damages to the plant. The aim of this study was to investigate how grapevine wood infested by larvae affects the mechanical properties of the plant in comparation with those of uninfested wood. Samples of grapevine wood uninfested and infested by larvae were collected from vineyards. Compression and flexural strengths as well as simulated structures of grapevine wood in field, in relation to harvest weight by variety, were used to quantify the wood mechanical properties. Infested wood endured a lower strength and normal tension, and exhibited a reduction in the structural capacities in the simulation of harvest weight of 'Cabernet-Sauvignon' variety (up to 62.0 %). 'Tempranillo' (despite its high mechanical slenderness values) and 'Cabernet-Sauvignon', were the varieties that showed a higher resistance on trunks and branches, respectively. A lower bending moment was observed on the infested branches of all varieties. Changes in the mechanical properties of infested wood suggest a decrease in mechanical resistance of wood attacked by larvae that could contribute to the rupture of the infested grapevine over time. Grapevine wood attacked by X. arvicola larvae could be more sensitive to mechanical external factors in vineyards such as strong winds, harvest weight and vibration exerted by harvesting machines.

Long-Term Creep Behavior Prediction of Sol-Gel Derived SiO2- and TiO2-Wood Composites Using the Stepped Isostress Method.

In this study, methyltrimethoxysilane (MTMOS), methyltriethoxysilane (MTEOS), tetraethoxysilane (TEOS), and titanium(IV) isopropoxide (TTIP) were used as precursor sols to prepare wood-inorganic composites (WICs) by a sol-gel process, and subsequently, the long-term creep behavior of these composites was estimated by application of the stepped isostress method (SSM). The results revealed that the flexural modulus of wood and WICs were in the range of 9.8–10.5 GPa, and there were no significant differences among them. However, the flexural strength of the WICs (93–103 MPa) was stronger than that of wood (86 MPa). Additionally, based on the SSM processes, smooth master curves were obtained from different SSM testing parameters, and they fit well with the experimental data. These results demonstrated that the SSM was a useful approach to evaluate the long-term creep behavior of wood and WICs. According to the Eyring equation, the activation volume of the WICs prepared from MTMOS (0.825 nm3) and TEOS (0.657 nm3) was less than that of the untreated wood (0.832 nm3). Furthermore, the WICs exhibited better performance on the creep resistance than that of wood, except for the WICMTEOS. The reduction of time-dependent modulus for the WIC prepared from MTMOS was 26% at 50 years, which is the least among all WICs tested. These findings clearly indicate that treatment with suitable metal alkoxides could improve the creep resistance of wood.

Enhanced Weathering Resistance of Radiata Pine Wood by Treatment with an Aqueous Styrene/Acrylic Acid Copolymer Dispersion

Radiata pine (Pinus radiata Don.) sapwood was treated with an aqueous dispersion solution of styrene/acrylic acid (St/AA) copolymer (5, 15, or 25%) and the treatment effect on weathering of wood was determined. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggested that the St/AA treatment delayed lignin degradation during artificial weathering; the protection effect increased with St/AA concentration. Decrease in water contact angle upon weathering for the treated wood was also slower than for the untreated control. Scanning electron microscopy revealed that the St/AA polymer filled some wood cell lumina, which facilitates to inhibit moisture and light (especially ultraviolet light) penetration into wood. During 12 months of outdoor exposure, the St/AA-treated wood boards had lower moisture content and less detachment of earlywood cells than the untreated controls. Treatments with St/AA stabilized the surface color by inhibiting photo-oxidation of cell wall polymers and propagation of staining fungi. The results suggest that treatment with St/AA can substantially improve wood’s resistance to weathering.

On the Effect of Heat Treatments on the Adhesion, Finishing and Decay Resistance of Japanese cedar (Cryptomeria japonica D. Don) and Formosa acacia (Acacia confuse Merr.(Leguminosae))

In Taiwan, it is important to maintain sustainable development of the forestry industry in order to raise the self-sufficiency of domestic timber. Japanese cedar (Cryptomeria D. Don and Formosa acacia (Acacia confusa Merr.(Leguminosae)) have abundant storage options and are the potential candidates for this purpose. Heat treatment is a new environment-friendly method used to enhance the dimensional stability and durability of wood. On treatment, a surface with new characteristics is produced because of wood component changes. Consequently, an inactivated surface and a weak boundary layer are generated, and the wettability for adhesives and coatings is reduced. Furthermore, it decreases the pH value of the wood surface, and results in delay or acceleration during the curing of adhesives. This phenomenon must be paid attention to for practical applications of heat-treated wood. Ideal heat-treated conditions of C. japonica and A. confusa woods with productive parameters such as temperature, holding time, heating rate, and thicknesses of wood were identified in our previous study. In this research work, we focus on the normal shear strength of heat-treated wood with adhesives such as urea-formaldehyde resin (UF) and polyvinyl acetate (PVAc), and the finishing performances of heat-treated wood with polyurethane (PU) and nitrocellulose lacquer (NC) coatings as well as assessing the decay-resistance of heat-treated wood. The results show that heat-treated wood had a better decay resistance than untreated wood. The mass decrease of heat-treated wood was only 1/3 or even less than the untreated wood. The normal shear strength of heat-treated wood with UF and PVAc decreased from 99% to 72% compared to the untreated wood, but the wood failure of heat-treated wood was higher than that of the untreated one. Furthermore, the adhesion and impact resistance of wood finished by PU and NC coatings showed no difference between the heat-treated wood and untreated wood. The finished heat-treated wood had a superior durability and better gloss retention and lightfastness than that of the untreated wood.

New Perspective on Wood Thermal Modification: Relevance between the Evolution of Chemical Structure and Physical-Mechanical Properties, and Online Analysis of Release of VOCs.

Thermal modification (TM) is an ecological and low-cost pretreated method to improve the dimensional stability and decay resistance of wood. This study systematically investigates the relevance between the evolution of chemical structure and the physical and mechanical properties during wood thermal modification processes. Moreover, the volatility of compounds (VOCs) was analyzed using a thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TGA-FTIR) and a pyrolizer coupled with gas chromatography/mass spectrometer (Py-GC/MS). With an increase of TM temperature, the anti-shrink efficiency and contact angle increased, while the equilibrium moisture content decreased. This result indicates that the dimensional stability improved markedly due to the reduction of hydrophilic hydroxyl (–OH). However, a slight decrease of the moduli of elasticity and of rupture was observed after TM due to the thermal degradation of hemicellulose and cellulose. Based on a TGA-FTIR analysis, the small molecular gaseous components were composed of H2O, CH4, CO2, and CO, where H2O was the dominant component with the highest absorbance intensity, i.e., 0.008 at 200 °C. Based on the Py-GC/MS analysis, the VOCs were shown to be mainly composed of acids, aldehydes, ketones, phenols, furans, alcohols, sugars, and esters, where acids were the dominant compounds, with a relative content of 37.05−42.77%.

Role of fallen logs in maintaining the species diversity of understory vascular plants in a mixed coniferous and broad-leaved forest in Hokkaido, northern Japan

One long-standing, unresolved issue in forest management is how to achieve high levels of biodiversity conservation and commercial forestry for timber production. Retaining fallen logs on the forest floor is effective in preserving the habitats essential for many wood-dwelling organisms. However, the contributions of fallen logs toward the plant species diversity of forest understories are less clear, even though the importance of fallen logs on the emergence and survival of coniferous seedlings and saplings is well known, especially in boreal forests. This study aimed to clarify the roles of fallen logs in the maintenance of species diversity of understory vascular plants in forests. We investigated species richness and the composition of vascular plants on 319 fallen logs and in 128 forest-floor quadrats (2 × 2 m) in a 4-ha plot in a mixed coniferous and broad-leaved forest in Hokkaido, northern Japan. We also measured canopy openness in summer, surface area, wood resistance, and moss cover of fallen logs, and soil thickness in forest-floor quadrats. Additive partitioning and permutational multivariate analysis of variance (PERMANOVA) were used to examine differences in composition between quadrats and fallen logs. Generalized linear model (GLM) and canonical correspondence analysis (CCA) were also applied to test the determinants of species richness and composition in quadrats and fallen logs. In total, 83 vascular plant species were identified. For woody and herbaceous plants, several species occurred predominantly on fallen logs in comparison with quadrats. Species richness of woody plants on fallen logs was positively affected by surface area and moss cover, and negatively by wood resistance; although in quadrats it was not significantly associated with any environmental factors. Herbaceous species richness on fallen logs was also negatively influenced by wood resistance. In contrast, herbaceous species richness in quadrats was positively associated with canopy openness. These results suggest that fallen logs promote plant species diversity, including herbaceous plants, by creating habitat conditions favored in forest understory environments. This study implies that leaving fallen logs on the forest floor at logging sites contributes toward plant diversity conservation.

Imaging of Internal Defects of Polymer-Modified Wood Using Total Focusing Method

Polymer modification can improve the stability and corrosion resistance of wood, but it could create defects inside wood during the modification processing. Detection of defects inside polymer-modified wood can reduce wood losses and prevent the occurring of defects. Data simulation and tomographic imaging of polymer-modified wood internal defects were carried out using electromagnetic waves with nondestructive testing. This study constructed the polymer-modified wood models, simulated the electromagnetic scattering wave, and used the total focusing method to perform tomography of the defects in the polymer-modified wood. By analyzing the imaging characteristics of different types of defects, the effectiveness of electromagnetic waves in the detection of internal defects of polymer-modified wood was proved. This method can be extended to test internal defects of other high molecular polymers.

Effects of brown-rot decay on the electrical resistance of wood and its mechanism

The objective of this study was to investigate the effect of decay on the electrical resistance (ER) of wood with a high moisture content (&gt; 45%) and to try to determine the mechanism. Poplar wood blocks were exposed to a brown-rot decay fungus (Gloeophyllum trabeum (Pers. ex. Fr.) Murr.) for 2 to 12 weeks to obtain different degrees of decay. The ER values of the non decayed and decayed wood at various moisture contents were measured using a voltammetry method and were statistically analyzed. It was found that the ER of the wood blocks decreased with the fungus exposure time. Changes in the ER were quick during the first 2 weeks of exposure, which suggested that it can be used to assess early wood decay. The ER values of the decayed wood at different moisture contents were generally lower than that of the non decayed wood. A large difference (approximately 50 kΩ) was found between them when the wood moisture content was above 45%. Further analysis showed that this was because of the increase in conductive ions in the wood, rather than an increase in the moisture content. These results may be helpful to better detect the internal decay of trees using ER-based methods and could partly explain ER differences in decayed trees.

Synergistic toughening effects of grafting modification and elastomer-olefin block copolymer addition on the fracture resistance of wood particle/polypropylene/elastomer composites

A novel wood particle/polypropylene/elastomer composites with good impact resistance and stiffness was prepared by adding elastomer-olefin block copolymer (OBC) and grafting maleic anhydride (MAH) on polypropylene/OBC blends. The grafted MAH greatly improved the interfacial interaction among polypropylene, OBC, and wood particle, resulting in an enhanced impact resistance, stiffness and dimensional stability of the resulting composites. The modified matrix and their composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, mechanical tests, and dynamic mechanical analysis. The results confirmed that with 60 wt% wood particles loading, the synergistic interactions between OBC blending and MAH grafting improved the impact strength of the MAH-grafted blends/wood particle composites by 49%, with stiffness comparable that of the MAH-grafted polypropylene/wood particle composites. The composites modified with MAH also revealed an enhanced interfacial adhesion among polypropylene, OBC, and wood particles, as evidenced by dimensional stability tests, dynamic mechanical analysis, and morphology observation.

Computational calculation of temperature and electrical resistance to control Joule heating of green Pinus radiata logs

This study describes a computational model employed to control Joule heating of green Pinus radiata logs in experiments on twenty export size logs from trees grown in the Canterbury region of New Zealand. The heating process was modelled using custom-built one-dimensional computational software based on the finite volume method (FVM). The proposed control method utilized the logs’ experimental bulk electrical resistance as a feedback variable during the Joule heating operation. As wood resistance is temperature dependent, comparing the experimental and predicted resistance values allowed an indirect determination of the actual wood temperature. The model accurately predicted the log resistance and the final log temperature, with an error of 6% and 5%, respectively. The limitations and further improvements to the model are discussed.

Decay resistance of two-step freezing–heat-treated fast-growing eucalyptus wood

The present study aimed at evaluating the decay resistance of Eucalyptus grandis wood modified by two-step freezing–heat treatments, using brown-rot (Gloeophyllum trabeum) and white-rot (Trametes versicolor) fungi. Five treatments, combining freezing (at − 22 °C) and termorretification (at 180 °C and 200 °C), were performed. The decay resistance tests were conducted as per relevant standard. Both freezing and thermal treatments were effective in reducing the mass losses attributed to the brown-rot fungus. The two-step treatment, in which the freezing was prior to the thermal treatment at 200 °C, yielded the highest decay resistance to the eucalyptus wood, leading to a hindered access to the nutrients in cellulose and hemicelluloses. Only two-step treatments were effective for protecting the wood against the white-rot fungus, which may be due to modifications in both lignin and wood extractives related to synergic effects from both freezing and heat.

Mechanical properties, components and decay resistance of Populus davidiana bioincised by Coriolus versicolor

The experiment was conducted to improve the decay resistance of wood by increasing the wood preservatives uptake and penetration depth by bioincising with Coriolus versicolor. The mechanical properties of bioincised Populus davidiana sapwood were measured. The changes of wood components (lignin, cellulose and hemicellulose) were analyzed by FTIR. The staining treatment using potassium permanganate was to measure the preservatives uptake and penetration depth in wood specimens. The decay resistance of bioincised specimens impregnated with IPBC and CA was assessed against C. versicolor and Gloeophyllum trabeum using bioincised P. davidiana sapwood and untreated controls. The results showed that the mechanical properties of the bioincised specimens were changed with the incubation time and mass loss. The mechanical strength was decreased after 17 days compared to that of the specimens bioincised < 13 days. The bioincised specimens demonstrated the deeper penetration depth than the un-bioincised specimens. It was significant correlation (P < 0.01) between penetration depth and incubation time. The average value of the penetration depth of the bioincised specimens was deeper than the control groups by 158.7%. By FTIR analysis, the biodegradation ability of C. versicolor to decay cellulose and hemicellulose was weaker than that of lignin. The bioincising treatment significantly increased the wood uptake of IPBC and CA, and reached the maximum uptake value at 17 and 13 days, respectively. Summarily, the bioincising pretreatment can obviously improve the wood decay resistance against C. versicolor and G. trabeum following by introducing the IPBC and CA.

Improving Wood Resistance to Decay by Nanostructured ZnO-Based Treatments

In this study, the maple wood surface was coated with nanostructured zinc oxide, grown on the surface by using a hydrothermal process, and furtherly treated with shellac varnish. Samples obtained both after ZnO treatment and after the final varnish application were characterized by different techniques, i.e., X-ray diffraction (XRD), scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS), micro-FTIR with attenuated total reflectance (μ-ATR-FTIR), chromatic variation measurements, and contact angle determinations. Analytical results showed that the wood surface was covered by quite a homogeneous array of inorganic nanoparticles and that the natural resin forms a regular film over the ZnO nanostructures. An accelerated aging test was used to evaluate the protecting effectiveness of the treatments towards UV-induced decay of wood material. After the test, wood treated with ZnO and with the shellac/ZnO combination underwent a considerably lower chromatic change if compared to the untreated wood, suggesting an enhanced resistance of the treated maple to the decay due to light exposition. The presence of nanostructured ZnO protects from decay not only the wood substrate but also the shellac film. A microbiology test showed that growth of fungal species, e.g., common mold, is prevented on the wood surface treated with ZnO or with shellac/ZnO, indicating that the nanostructured zinc oxide also provides an effective protection from biodeterioration. The coating obtained by consecutive application of nanosized ZnO particles and shellac varnish combines the excellent aesthetical features and water repellence of the traditional finish with the protecting effectiveness of the nanostructured inorganic component.

Abrasion Resistance of Thermally and Chemically Modified Timber

Wood modification is an appropriate way of improving the natural durability and dimensional stability of wood without the use of biocides. Different thermal and chemical wood modification processes are available for this purpose, very differently affecting the structural integrity of wood. In this study, thermally modified, melamine resin treated, acetylated, furfurylated, and mDMDHEU treated wood underwent abrasion tests according to two different methods representing different loads in practice. The Taber Abraser method caused crosswise cutting into the wood surface, while the Shaker method challenged mainly the specimen edges with dynamic loads. Abrasion resistance of wood was affected by all types of cell wall modification, but the effects were strongly dependent on the type of modification and the applied load type. For characterising the suitability of wooden materials with respect to wear resistance under outdoor conditions, it is recommended to apply a set of methods rather than a single test procedure to fully reflect the loads occurring in practice.

Heat-Treated Wood as a Substrate for Coatings, Weathering of Heat-Treated Wood, and Coating Performance on Heat-Treated Wood

Heat treatment is a method of wood modification with increasing market acceptance in Europe. The major patented European commercial heat treatment processes have trade names ThermoWood, Platowood, Retiwood, Le Bois Perdure, and Oil-Heat-Treated Wood (OHT). To what extent modification of wood affects the resistance of wood to weathering is also an important aspect for wood applications, especially where appearance is important. Unfortunately, heat-treated wood has poor resistance to weathering, and surface treatment with coatings is required for both protection and aesthetic reasons. As a substrate for coating, heat-treated wood has altered characteristics such as lower hygroscopicity and liquid water uptake and changed acidity, wettability, surface free energy, and anatomical microstructure. Various wood species, heat treatment method, treatment intensity, and treatment conditions exhibited a different extent of changes in wood properties. These altered properties could affect coating performance on heat-treated wood. The reported changes in acidity and in surface energy due to heat treatments are inconsistent with one another depending on wood species and temperature of the treatments. This paper gives an overview of the research results with regards to properties of heat-treated wood that can affect coating performance and weathering of uncoated and coated heat-treated wood.

Genetic Variation in Acoustic Time of Flight and Drill Resistance of Juvenile Wood in a Large Loblolly Pine Breeding Population

AbstractAcoustic time of flight and drill resistance (surrogates for wood stiffness and density, respectively) were measured on 11,097 standing trees from 269 pollen-mix families of loblolly pine (Pinus taeda L.) in 6- to 9-year-old progeny tests at eight sites across the southeastern United States. Specific gravity was measured on two test sites. The phenotypic correlation between specific gravity and drill resistance was moderate (r = 0.68), whereas the genetic correlation was very strong (rg = 0.96). Narrow-sense heritabilities for acoustic time of flight and drill resistance were around 0.35 for individual trees and very strong (0.90) for family means. High genetic correlations (&amp;gt;0.80) between pairs of sites suggested a low genotype-by-environment interaction for both traits. Genetic correlations between wood quality traits and other economic traits (growth and stem straightness) were low except for a moderate correlation between acoustic time of flight and tree slenderness (rg = –0.64). The checklot ranked near the middle for both wood quality traits, implying no inadvertent selection occurred in this population that has been selected intensively for volume productivity. This study is the first to apply these tools in a large breeding program, and results suggest they are effective for selecting genotypes for wood quality.

Technologies for Manufacturing of Moisture-Resistant Products from Modified Wood

Wood, as a finishing and building material, has always been given special attention. Wood has many positive properties, but it's no secret that faced with its shortcomings such as fragility, instability of form and susceptibility to decay, people often prefer synthetic materials, putting aside the ecology and useful properties of wood and choosing the long life of non-natural materials. In this regard experts around the world are constantly searching for new solutions aimed at improving the physical, mechanical and operational properties of wood, which would allow a person to limit the use of artificially created analogs of natural materials and enjoy the atmosphere of tranquility and appeasement in a house that can create a tree. Analyzing the knowledge and skills of previous generations the author of the article took as a basis various technologies of deep processing with the aim of improving the quality, extending the service life and expanding the scope of its use, thanks to which a new modern moisture resistant "hardened" tree is created for furniture, interior, finishing elements for garden houses and plots. Experiments have been carried out to investigate the biological resistance of wood thermo modified in five different technologies: vacuum-convective thermal modification in a superheated steam, convective thermal modification in a saturated high-pressure steam environment, thermal modification of wood in hydrophobic liquids, thermal modification of wood in a flue gas environment and vacuum-conductive thermal modification. The degree of moisture resistance of the samples is calculated, which makes it possible to conclude that the mass of thermo-modified wood is significantly lower, caused by the destructive effect of fungi, as compared to untreated samples. The most optimal technology for structures involving close contact with water or soil is determined.

Effect of the degree of decay on the electrical resistance of wood degraded by brown-rot fungi

There have been limited efforts to investigate the association between wood decay and electrical resistance; consequently, we have examined the change in the electrical resistance of wood progressively decayed by brown-rot fungi to elucidate the effect of the degree of decay. The rate of mass loss of wood was used as an indicator of the degree of fungal decay. The changes in the moisture content and ion concentrations were measured at various decay stages. The results showed a significant difference in the electrical resistances of sound wood and fungal-treated wood after 24 weeks. The electrical resistance significantly decreased with the exposure time. The degree of decay increased as the mass loss increased, resulting in the severe breakdown of cell walls and the accumulation of fungal mycelia. Empirical models related to the rate of mass loss and the percent decrease in the electrical resistance were established. The moisture content and cation concentrations increased to various degrees in decayed wood. This increase in the cation concentration was considered to play a dominant role in the decrease in the electrical resistance. The study results provide valuable information for developing an electrical resistance based method coupled with ion content measurements for incipient wood decay detection.

Improvement of mechanical, humidity resistance and thermal properties of heat-treated rubber wood by impregnation of SiO2 precursor

The SiO2 precursor solution was impregnated into heat-treated rubber wood to enhance its mechanical and flame-retarding properties. Test specimens were randomly divided into four groups, i.e., untreated (U), heat-treated (HT), impregnated SiO2 precursor before heat treatment (ISB) and after heat treatment (ISA). Results showed that, compared with HT wood specimens, the modulus of rupture (MOR) and compression strength of ISB and ISA wood specimens were both increased. The hygroscopicity of modified wood was decreased and the dimension stability was consequently improved. Surprisingly, the hardness of ISB specimens increased by 43.65%. The thermogravimetric (TG) examination showed that the incorporation of silicon retarded the thermal decomposition and improved the thermal stability of wood. Furthermore, the scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) revealed that the SiO2 gel was deposited in the cell wall, The Fourier transform infrared spectroscopy (FTIR) showed the formation of Si–O–Si and Si–O–C covalent bonds. The X-ray diffraction (XRD) tests indicated that the impregnation of SiO2 precursor had slight effect on the crystalline structure of the wood.