Water repellency in treatedHevea brasiliensis andMangifera indica wood

Samples of rubber (Hevea brasiliensis) and mango (Mangifera indica) wood treated with 2.5%, 5%, 7.5% and 10% aqueous solution of Chromic acid were assessed for water repellency and dimensional stability. Significant reduction in water absorption in treated samples was observed in initial five hours of soaking in water compared to untreated controls. It was found that effectiveness of water repellency was independent of concentration of solution under repeated cycles of wetting and drying. Degree of water repellency that could be achieved by chromic acid treatment appears to be dependent on constituents of wood.     

Dimensional stability and hardness improvement of southern yellow pine wood using divinylbenzene dioxide

Wood is commonly used as a construction material for floors, outdoor decks, house framing, bridges etc. However, the dimensional instability of wood has limited its use in these and other applications. This is due in part to the constant adsorption and release of water which results in swelling and shrinking leading to the physical degradation of the wood (Kumar 1994). A variety of treatment methods has been developed in an attempt to improve the hardness, stability, stiffness, and dimensional stability of wood. However, many of these methods are not economic or commercially scalable. There still exists a need for a commercially viable wood treating technology which will provide increased dimensional stability and hardness. This article details a wood treating method using a difunctional epoxide cured with a catalyst at low temperature inside of the wood to prepare a wood polymer composite (WPOC). Analysis by scanning electron microscopy (SEM) and micro infrared spectroscopy (micro IR) showed the epoxy resin was distributed uniformly throughout the wood including the cell wall. The epoxide treated wood compared to untreated wood showed improvements in hydrophobicity (water repellency), anti-swelling efficiency (ASE) as a measure of dimensional stability, hardness, and three-point bending dynamic mechanical analysis (DMA) properties.     

Evaluation of potential use of nootkatone against maize weevil (Sitophilus zeamais Motschulsky) and rice weevil [S. oryzae (L.)](Coleoptera: Curculionidae)

Nootkatone is a natural sesquiterpene ketone that shows insecticidal activity against insects and ticks. Its contact toxicity and repellency against two major stored-product insect pests, maize weevil (Sitophilus zeamais Motschulsky) and rice weevil [Sitophilus oryzae (L.)], were investigated in the current study. Contact toxicity was evaluated using a no-choice test with treated filter paper, while repellency was evaluated using a choice test with treated corn (for maize weevils) or wheat (for rice weevils). Nootkatone showed low contact toxicity (ranging from 0 to 51%) against the two weevil species at the tested concentrations (ranging from 11.58 μg/cm² to 1158.08 μg/cm²) on filter papers. In choice tests, corn treated with 0.10% or higher and wheat treated with 0.5% nootkatone or higher had significantly fewer maize or rice weevils compared with the solvent only treated control, indicating a repellent effect. The repellency percentage ranged between 46.3 and 93.1% against maize weevils and 39.2-67.2% for rice weevils.     

Effects of water glass and DMDHEU treatment on the colonisation of wood by Aureobasidium pullulans

Specimens of Scots pine sapwood (Pinus sylvestris) and beech (Fagus sylvatica) were treated with a sodium water glass solution and 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU). The pH-values of water glass treated specimens were between 9.7 and 12.0. Those of DMDHEU treated specimens were 3.8 (Scots pine) and 4.2 (beech). The resistance observed in an eight weeks laboratory test against the blue stain fungus Aureobasidium pullulans showed that treatments with water glass and DMDHEU reduced but not prevented the fungal growth. Wood specimens treated with water glass showed the lowest colonisation of blue stain. Both treatments inhibited fungal penetration through the ray cells. HPLC analysis showed that the amount of simple sugars was reduced due to water glass treatment. The amount of simple sugars in DMDHEU treated wood depended on the wood species. The amount of available sugar monomers did not indicate an influence of the colonisation of the sample surface.     

Use of wax emulsions for improvement of wood durability and sorption properties

Waxes are used for treatment of wood surfaces for several decades predominately as surface treatments because they weakly penetrate into the wood. In order to overcome this issue, water emulsions were applied in the present experiment. Five water emulsions of various concentrations were used, namely montan wax, polyethylene, ethylene copolymer and oxidized polyethylene wax. Performance of wax treated beech (Fagus sylvatica) and Norway spruce (Picea abies) against white rot, brown rot and blue stain fungi was tested. In parallel, sorption properties of wax treated wood were determined. The treated specimens were more resistant to wood decay fungi. Polyethylene and oxidized polyethylene wax were found to be particularly efficient. Although this treatment does not improve resistance to blue stain fungi, it reduces the sorption of water.     

Effect of heat treatment on the wettability of white ash and soft maple by water

Heat treatment of wood has attracted a lot of attention both in Europe and recently in North America as an environmentally-friendly wood-protection method. The untreated wood is hydrophilic (high affinity for water). During the heat treatment, wood becomes more and more hydrophobic (low affinity for water) with increasing heat treatment temperature. As a result, it becomes more resistant to biological attacks. Furthermore, it becomes dimensionally more stable compared to untreated wood. Its hardness increases. As the wood becomes more hydrophobic, its wettability by water decreases. The effect of heat treatment is different for each species. Studying the wetting characteristics of heat treated wood gives a good indication of the heat treatment effects on certain wood properties which are related to its degree of hydrophobic character. The aim of this work was to study the characteristics of dynamic wetting process for two different heat-treated North American wood species white ash (Fraxinus americana) and soft maple (Acer rubrum). Contact angle measurements before and after heat treatment showed a significant increase in wood hydrophobicity. Advancing contact angles of a water drop were in all cases higher for heat-treated wood than for untreated wood.     

Weathering characteristics of wood treated with water glass, siloxane or DMDHEU

Specimens of Scots pine sapwood (Pinus sylvestris) and beech wood (Fagus sylvatica) were treated with a sodium water glass solution, an amino-alkyl-functional oligomeric siloxane and 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU). The specimens were exposed outside without ground contact for 24 months. Colour measurements during outside exposure showed a discoloration of all wood specimen surfaces. FTIR spectroscopy displayed lignin degradation of all specimens during the initial exposure time. Chemical treatments decelerated fungal infestation of wood, while their effect on lignin degradation was not discernible. SEM studies revealed that fungal infestation was affected by the different treatments. The untreated specimens showed radial penetration of fungal hyphae through the pits. Only superficial infestation and no radial penetration were visible at water glass and siloxane treated specimens. A significantly reduced radial penetration of fungal hyphae was exhibited at DMDHEU treated specimens. Fungal infestation through the pits was not visible.     

Improving the UV and water-resistance properties of Scots pine (Pinus sylvestris) with impregnation modifiers

Wood modification is commonly used to alter and improve wood properties. This study investigates the effects of impregnation modification with four environmentally nontoxic agents on the UV-resistance and water absorption properties of solid wood. Scots pine (Pinus sylvestris) was impregnated with modifiers by pressure device. The solid wood specimens were treated with water glass, silicone, melamine, and tall oil. The modified samples were analyzed by SEM microscopy, and thickness swelling, water absorption and UV resistance were determined. The penetration of the studied modifiers differed. The melamine-treated samples were found to exhibit the best impregnation, which also affected the wood properties favorably. The melamine-treated solid pine wood samples absorbed half of the water absorbed by wood treated with the other solutions and attained the best results in thickness swelling and weathering tests. It is concluded that impregnation modification of Scots pine is dependent on the nature of the modifier and based on the results of this study, melamine solution treatment is found to have a positive effect on the properties of solid pine wood.     

Influence of thermo-vacuum treatment on thermal degradation of various wood species

Solid wood has a certain amount of resistance to fire exposure. Recently, there is also great interest in characterization of the thermal behaviour of treated wood due to increasing demand of such products within the perspective of sustainability of environment. The objective of this study was to evaluate and predict the thermal decomposition process of samples from different wood species, Norway spruce (Picea abies Karst.), common ash (Fraxinus excelsior L.) and Turkey oak (Quercus cerris L.), so that such data can be used for enhanced design of wood products for more effective and better utilization in different applications. Spruce and ash samples were treated at a temperature of 190 °C for 2 h while Turkey oak specimens were steamed at a temperature of 110 °C for 24 h before they were thermally treated at a temperature of 160 °C for 3 h. A thermo-gravimetric analysis of the samples highlighted intraspecific differences in mass loss and the stage of thermal degradation between treated and untreated specimens. The degradation of the wood was characterized by twofold reaction stages, with an exception of Norway spruce samples, which exhibited a one-stage reaction. In addition, thermal treatments affected chemical composition of wood. The obtained results will be helpful in determining the applicability of these materials according to their thermal degradation properties.     

Investigation of the plasma effects on wood after activation by diffuse coplanar surface barrier discharge

Sample material from spruce (Picea abies), beech (Fagus sylvatica) and ash (Fraxinus excelsior) with radial and tangential section was treated by diffuse coplanar surface barrier discharge (DCSBD) plasma generated in air at atmospheric pressure. Plasma activated samples exhibited significantly lower water uptake times of 50 μl droplets and minimal differences in wetting between the two cutting planes (radial and tangential), when compared to the untreated surface. Simultaneously, more uniform spreading of the droplets and increased area of wetting on the activated surface were achieved. The plasma treatment had no effect on the water absorption coefficient of the wood samples. FTIR measurements confirmed the presence of oxygen containing functional groups and structural changes in lignin on the activated wood surface. The minimal heating of the treated samples suggests this method to be applicable to treat heat sensitive wooden materials.     

How far does a gaseous reagent penetrate into wood

The reaction between wood components and vaporous formaldehyde was applied to the evaluation of gas permeability and forecast of the extent where the reaction occurs. The structural changes of pre-compression wood, which is a new method to suck the liquid reagent by the recovery force, was also followed by the established method. The formaldehyde content (y) reacted with wood components decreased exponentially as according as the depth from the penetrating surface. It could be expressed by the distance from surface, x, for both longitudinal and tangential directions as follows; y=kexp(?ax) where, a and k are constants for individual wood samples. The half-interval (a definite distance of half reduction), d _1/2, was defined by (ln 2)/a. The reaction level at the arbitral inner portion of wood can be estimated by both the half-interval and the reaction level at the vicinity of surface region. The use of the structural changes of pre-compression wood is suggested.     

Effect of oil heating age on colour and dimensional stability of heat treated Pinus radiata

Pinus radiata specimens with moisture content of 8–11% and dimensions of 90×35×200 mm³ were heat-treated in an oil bath of commercial grade raw linseed oil. The effect of oil aging was investigated under treatment condition of 180°C and 3 hours by using oil that had been preheated for 0, 3, 9, 15, 21, and 27 hours, respectively, before the wood treatment. After treatment using oils of varying ages, wood colour change was examined using a Minolta spectrophotometer through CIE 1976 (L ^* a ^* b) system. Water repellent efficiency and anti swelling efficiency in high humidity conditions were measured to determine the stability of the treated wood. The results show that stability of the treated wood was improved significantly compared to the matched untreated wood but the treated wood tended to be darker. Oil viscosity increased with the heating age resulting in slight decrease in weight percentage gain. Water repellent efficiency was decreased with an increase in heating age of oil. However no significant difference in total colour variation and wood stability (anti swelling efficiency) was observed between specimens treated with oils of varying heating age.     

Resistance of modified polyvinyl chloride/wood flour composites to basidiomycetes

Aminosilane, melamine and acetic anhydride treated wood flour were added to polyvinyl chloride (PVC) and manufactured into wood-plastic composites (WPC) panels in order to investigate the influence of modification on the resistance to basidiomycetes of the composite. The composite consisted of 50 wt% wood and 50 wt% PVC dry blend. White rot (Trametes versicolor) and brown rot (Coniophora puteana) fungi were used to inoculate the composite. Test procedure was carried out according to ENV 12038 with an additional water pre-treatment of the composite. All tested formulations showed high resistance to basidiomycetes under the test conditions. With regard to the modifications used, only aminosilane treated composites showed slightly decreased weight loss values compared to the untreated reference.     

A simple and effective method for detecting toxicity of chromium trioxide on Vicia faba

In modern biological research, there are many analytical methods to evaluate the toxicity caused by chemical agents, such as higher plant bioassay, flow cytometry, single-cell gel electrophoresis or the comet assay. However, these methods are either tediously experimental procedures or require a high-tech platform. In this study, the effects of chromium trioxide (CrO₃) on the primary root growth of Vicia faba seeds over 72 h were investigated. The primary root length of seeds cultivated in different concentrations of CrO₃ was collected and analyzed. It was indicated that the Vicia faba seeds maintained a good growing state when the CrO₃ concentration was below 100 μmol/L, while the root growth was suppressed when they were kept in 250 μmol/L of CrO₃ for 72 h or cultured with CrO₃ concentrations above 500 μmol/L. In comparison with the chromosome aberration bioassay, the primary root length assay is proved in this paper to be a simple and effective alternative for water toxicity testing in areas where heavy metal pollution has become serious.     

Fungal and termite resistance of wood treated with 4-methoxytrityl tetrafluoroborate

This study evaluates the decay and termite resistance of Scots pine (Pinus sylvestris L.) treated with 4-methoxytrityl tetrafluoroborate (MTFB). Decay resistance tests of unleached samples showed that 2%, 1.5% and 1% concentrations of MTFB (15.4 kg/m³, 11.1 kg/m³, and 7.4 kg/m³, retention levels, respectively) gave less than 2% decay of Postia placenta and concentrations of 2% and 1.5% less than 2% decay of Coniophora puteana. Wood specimens treated with 4-methoxytrityl tetrafluoroborate solutions were not protected against the brown rot fungi after a 14-day severe leaching process, suggesting excessive leaching of the chemical from wood. Treatment with 2% concentration protected against subterranean termites, Coptotermes formosanus Shiraki based on mass losses in both leached and unleached wood specimens in comparison with lower concentration levels. These results suggest that 4-methoxytrityl tetrafluoroborate might be promising to protect wood being used outdoors against termite attack. However, 4-methoxytrityl tetrafluoroborate did not protect wood against fungal decay. Field tests are needed to observe the performance of 4-methoxytrityl tetrafluoroborate treated wood in ground contact.     

Effect of hot air post-treatments on copper leaching resistance in ACQ-D treated Chinese fir

Chinese fir (Cunninghamia lanceolata Hook.) wood cubes (19?×?19?×?19 mm³) were treated with amine copper quat-type D (ACQ-D) solution and fixed with different hot air post-treatments. The effects of temperature, relative humidity, duration, air circulation of post-treatment as well as the copper retention in the treated wood on copper leaching were investigated. With the help of ultraviolet or visible spectroscopy (UV/VIS), the valence conversion of copper in treated wood post-treated with optimal post-treatment conditions was investigated, and its relation with copper leaching was also discussed. The results showed that besides temperature and relative humidity, air circulation during hot air post-treatments also had a significant effect on accelerating copper fixation in ACQ-D treated wood. 70 °C, 80% R.H. with good air circulation provided a suitable condition for complete fixation of copper in a short period. After the applied post-treatments, up to 11.3% cupric copper reduced to cuprous form. A higher copper conversion rate usually corresponds to lower copper leaching, which is consistent with the contribution of lower water solubility cuprous copper.     

Effect of essential oil compounds and plant extracts on decay and termite resistance of wood

Essential oils and their derivatives have a long history of safe usage as antimicrobial agents in food industry. In this study various essential oils and extracts from plants were screened for their ability to inhibit wood decay and termite attack in laboratory decay and termite resistance tests using treated wood specimens. In the laboratory decay resistance tests, wood specimens treated with essential oil compounds were subjected to brown-rot fungus, Tyromyces palustris, and white-rot fungus, Trametes versicolor for three months. The specimens were also subjected to termite attack by subterranean termites, Coptotermes formosanus for three weeks in laboratory conditions. The formulation with cinnamaldehyde (DF3) was found to be effective against both the brown-rot and white-rot fungi used in the study. However, the formulation with cinnamic acid (DF8) was able to protect wood specimens against only the white rot fungus and about 50% mass loss occurred in the specimens subjected to the brown-rot fungus. The mass losses in the wood specimens treated with cassia oil containing formulation (DF4) showed that cassia oil was effective against both fungi. The wood tar oil and dodecanal compounds also inhibited fungal decay in the specimens. The wood specimens treated with the formulations used in termite resistance tests were more resistant against the termites when compared to specimens treated with the formulations in decay resistance tests. Even after severe weathering process, treated wood specimens showed resistance against the subterranean termites. Results suggest that essential oils and plant extracts might be important to develop new wood preservatives that are less harmful to the environment and humans than recently available ones.     

Structural characterisation of a water-soluble polysaccharide with high branches from the leaves of Taxus chinensis var. mairei

A large number of polysaccharides present in the leaves of Taxus chinensis var. mairei were successively extracted with hot water after preliminary treatments. The ion-exchange and gel-permeation chromatography was used to isolate and purify the major polysaccharides to afford a complex water-soluble polysaccharide, named T1 with a molecular mass of 3.44 × 10⁶ Da determined by HPGPC. T1 consisted of 2,4-di-O-methyl-mannose, rhamnose, arabinose, xylose, galactose, mannose, galacturonic acid and glucuronic acid in a molar ratio of 2:5:24:9:3:46:1:10, and the acetyl content was estimated to be 2.1%. On the basis of methylation analysis, periodate and chromium trioxide oxidations, Smith degradation, graded acid hydrolysis, and NMR and IR spectroscopy, T1 possessed a 1,3,6-linked β-d-Manp main chain, substituted by mannose, arabinose, galactose, xylose, rhamnose, 2,4-di-O-methyl-mannose, galacturonic acid, and glucuronic acid residues. These contained non-reducing end-units of mannose, arabinose, xylose, 2,4-di-O-methyl-mannose, and glucuronic acid. This is the first report on isolation of an acid heteropolysaccharide from Taxus species.     

Laboratory evaluation of boron-containing quaternary ammonia compound, didecyl dimethyl ammonium tetrafluoroborate (DBF) for control of decay and termite attack and fungal staining of wood

This study evaluates the decay and termite resistance of wood treated with didecyl dimethyl ammonium tetrafluoroborate (DBF), a recently developed quaternary ammonia compound containing boron. Laboratory decay resistance tests were performed using brown-rot fungus, Fomitopsis palustris and white-rot fungus, Trametes versicolor. Treated wood specimens were also subjected a 3-week-termite resistance test using subterranean termites, Coptotermes formosanus. Decay resistance tests showed that wood specimens treated with 0.5 and 1.0% DBF solutions were well protected against both fungi even after a 10-day severe leaching process, suggesting the adequate fixation of DBF in wood. DBF treatment at 0.1% concentration was efficient against subterranean termites, Coptotermes formosanus Shiraki based on mass losses in both leached and unleached wood specimens. The ability of DBF to inhibit discolorations by selected mold and stain fungi was also screened in laboratory conditions. DBF at the highest concentration level (1%) provided limited protection against mold and staining fungi tested, however, it was effective for only short-term protection (1 or 2 weeks) at lower concentrations. These results suggest that DBF is promising to protect wood to be used outdoors against both fungal decay and termite attack however field tests are needed to observe the performance of DBF-treated wood in ground contact.     

Survival of Listeria monocytogenes after cleaning and sanitation of wooden shelves used for cheese ripening

The effect of cleaning and heat disinfection processes of wooden shelves used for cheese ripening on the survival of Listeria monocytogenes was examined. The cut boards were inoculated with a suspension containing 5.5?×?10⁷ colony forming units (CFU)/ml of L.??monocytogenes. Survival of L.??monocytogenes was investigated in the wood shavings. During the 24-hour incubation period in a humidity chamber, Listeria counts increased by 0.8 log units on average (n?=?9), compared to results 1?h after incubation, indicating the absence of antimicrobial properties of the wood in use. Additionally, after incubation for 24?h at room temperature, the boards were cleaned by soaking them for 15?min in a solution of hot alkaline detergent followed by brushing and rinsing with warm water. Some of the cleaned boards were subsequently heat treated at 80°C for 5?min and at 65°C for 15?min, respectively. The cleaning procedure alone was not sufficient to render L.??monocytogenes from the upper 2?mm wood layer inactive. In the case of both temperature-time combinations for heat disinfection, however, L.??monocytogenes was not detectable. The present study shows that the use of wooden shelves does not affect the hygienic safety of cheeses if such shelves are in good repair and are thoroughly cleaned and sanitized by heat treatment. Therefore, there is no reason to replace wood employed in cheese ripening processes with other materials.