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.     

Effect of heat treatment intensity on wood chemical composition and decay durability of Pinus patula

Heat treatment is an effective method to improve biological resistance of low natural durability wood species. The aim of this study was to enhance the decay resistance of Pinus patula, an African low natural durability softwood species, via wood thermal modification technique. Heat treatment was performed on wood specimens under inert conditions at different heat treatment intensities to reach mass losses of 5, 10 and 15%. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta. The wood chemical and elemental composition was determined as well as extractives toxicity before and after wood thermal modification to understand the reasons of durability improvement. The treated specimens exhibited a significant increase in their durability against wood decay in line with the severity of the treatment. Wood holocellulose was found to be distinctly more sensitive to the heating process than the lignin constituent. In addition, obvious correlations were observed between weight losses recorded after fungal exposure and both holocellulose decrease and lignin ratio increase. The same correlations were observed with the elemental composition changes allowing using the observed differences for predicting of wood durability conferred by heat treatment. Furthermore, no significant differences were observed between the toxicity of Pinus patula wood extractives before and after its thermal modification.     

Copper and aluminium deposition by cold-plasma spray on wood surfaces: effects on natural weathering behaviour

Atmospheric pressure plasma was used to deposit thin layers of copper and aluminium micro-particles on the surface of Scots pine sapwood (Pinus sylvestris L.) boards. Three different loadings of metal particles were established. Additional wood boards were topcoated with a commercial acrylic binder. Boards were exposed to natural weathering for 18 months. Discolouration of copper-treated boards was slowed down, and the treatment at highest loading displayed the best appearance. Aluminium treatment was not sufficient to prevent or reduce discolouration. The application of an acrylic binder as topcoating enhanced the general appearance of metal-treated boards. Evaluation of treated boards did not reveal any reduction in crack formation or water uptake due to the particle deposition. Infrared spectroscopy suggested that copper does not protect lignin from photo-degradation. Nevertheless, copper treatment reduced fungal infestation on wood; at highest copper loading, blue stain did not penetrate through the treated surface.     

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 boron in CCB formulation on growth and decay capabilities of copper tolerant fungi

The influence of boron in CCB preservative on infestation of leached and non-leached CCB treated wood specimens by copper tolerant and copper sensitive brown rot decay fungi are described. The tests were performed according the EN 113 procedure using seven different brown rot fungal strains: (Antrodia vaillantii (four different strains), Poria monticola, Gloeophyllum trabeum and Leucogyrophana pinastri). Leaching of boron from the CCB-treated wood samples rendered them susceptible to decay by the copper tolerant strains but not the copper sensitive ones. Additionally, using EPR spectroscopy, non-toxic copper oxalate was found in samples exposed to the copper tolerant strains (A. vaillantii and L. pinastri), as well as the copper sensitive strain P. monticola but not in the samples exposed to the other copper sensitive strain G. trabeum. It is supposed that, in the case of samples that were not leached before exposure to the copper tolerant fungi fungal growth and decay were inhibited by boron.     

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.     

Efficacy of Silicosec, filter cake and wood ash against the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) on three maize genotypes

The effectiveness of the diatomaceous earth Silicosec, a mineral industrial filter cake and domestic wood ash, applied at three different rates for the control of the maize weevil, Sitophilus zeamais, on three maize genotypes was determined. Treatment with Silicosec was the most effective followed by filter cake and wood ash. The treatments reduced progeny emergence, percentage grain damage and grain weight losses, but did not affect percentage seed germination. Grain treated with wood ash at all rates resulted in a relatively low mortality 3 days after infestation as compared to other treatments. However, all treatments caused high mortality (97-100%) after 15 days of exposure. Therefore, Silicosec, filter cake and wood ash can be considered as potential components of an integrated pest management strategy against the maize weevil.     

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.     

Effects of silver nanoparticles and fungal degradation on density and chemical composition of heat-treated poplar wood (Populous euroamerica)

Effects of silver nanoparticles and fungal degradation on the weight loss and chemical composition of heat-treated poplar wood were studied. Wood blocks were impregnated with a 400 ppm nanosilver suspension under 3 bar pressure for 20 min using Lowry process (edited empty cell). Heat-treatment was carried out at 135, 160 and 185 °C. Specimens were divided into 4 groups; control, nanosilver impregnated, heat-treated and impregnated- heat treated specimens (135, 160 and 185 °C). All samples from the internal and superficial parts of the blocks were exposed to the white rot fungus Trametes versicolor. The results of heat-treated samples indicated higher amount of Klason lignin and extractives, but lower holocellulose and cellulose content. Furthermore, heat-treatment illustrated an increasing effect on the fungal resistance. For all the properties, significant difference was found between the internal and superficial test specimens. Nanosilver impregnation had an intensifying effect on the results of the heat-treatment.     

Characterization of trembling aspen wood (Populus tremuloides L.) degraded with the white rot fungus Ceriporiopsis subvermispora and MWLs isolated thereof

Trembling aspen wood (Populus tremuloides L.) was treated with white rot fungus Ceriporiopsis subvermispora for 1, 2, 4, and 6 weeks. As fungal decay advanced, lignin contents were decreased gradually up to ca. 27.5% (based on the Klason residues of the control) after 6 weeks. Alkali solubility of cell wall residues was increased until 4 weeks of fungal treatment, but additional treatment did not cause any effects. Milled wood lignins (MWLs) were isolated from the decayed woods by Björkman’s procedure and subjected to thioacidolysis and analytical pyrolysis to investigate the modification of lignin structures during fungal degradation. Thioacidolysis revealed that the yields of trithioethylated C₆C₃ monomers, as a parameter for frequency of β-O-4 linkages in lignin, were substantially reduced (-20%, based on the control) in MWLs isolated from decayed woods. Analytical pyrolysis revealed that the relative amounts of coniferyl alcohol and sinapyl alcohol in the pyrolysates were lowered dependent on the biodegradation time, whereas an elevation of C₆C₁ and C₆C₂ pyrolytic phenols was observed. The results from both analytical methods strongly suggested that β-O-4 linkages were cleaved by C. subvermispora. Specially, degradation of syringyl-type lignin seems to be preferred.     

Effects of nanowollastonite on biological resistance of medium-density fiberboard against Antrodia vaillantii

The effect of wollastonite nanofibers (NW) on biological resistance of medium-density fiberboards (MDF) made from wood and chicken-feather fibers (CF) against Antrodia vaillantii was studied. NW content of 10 % and CF content of 5 and 10 %, based on the dry weight of wood fibers, were applied to the MDF matrix, giving a total of six different MDF mixing treatments. Mass loss values were measured roughly following the EN 113 specifications. The results showed that NW significantly decreased mass loss to a considerable extent in all mixing ratios, proving its potential to be used as a suitable preservative in wood-composite materials without environmental hazards. A CF content of 5 % showed improving effects on biological resistance, while CF of 10 % was too high and resulted in a weak MDF-matrix; eventually the biological resistance did not improve properly. NW ameliorated part of the undesirable effect of adding chicken feather fibers to the MDF-matrix. A significantly high correlation was found between mass loss versus water absorption (R ² of 81 %), implying that the penetration of water and fungal hyphae can have rather similar patterns. It can be concluded that NW not only can be used to improve the biological resistance in wood-composite materials against fungi attack, but it can also reduce some of the undesirable properties of chicken feathers, thus providing a reliable and renewable resource for natural fibers to be used in the MDF manufacturing industry.     

Reaction of wood with inorganic salts

Wood samples and veneers of Hevea brasiliensis (Rubber wood) and Acacia auriculaeformis treated with aqueous solutions of chromium trioxide, ferric chloride and ferric nitrate were studied for water repellency and their reaction with wood constituents. FTIR spectra obtained from wood surface treated with chromium trioxide indicate the formation of a water insoluble complex between chromium trioxide and aromatic ring of lignin, whereas no reaction takes place with ferric salts. Treatment of wood by chromium trioxide was found to be effective in imparting water repellency in wood.     

Vorbehandlung von Fichtenholz mit Chemikalien mit dem Ziel der Verbesserung der Imprägnierbarkeit

Dried sprucewood (Picea abies L. Karst) is hardly penetrable with liquids, p.e. wood preservatives. The aim of this research was to improve the penetrability by means of pretreatments with chemicals. Small specimens (20×20×50 mm) were treated with different acids, alkali and chelating agents. Concentration, temperature and duration were varied. Subsequently, the specimens were impregnated with a water based preservative. The penetration and the retention of the liquid were determined. The pre-treatments with ammoniumoxalate, acetic acid and formic acid improved the penetrability slightly without attacking the wood structure. For further work with sawn planks, acetic acid, hexametaphosphate and oxalate were selected (see part 2).     

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.     

Utilisation of chemically modified lampante oil for wood protection

Within the Slovenian region of Istria, the olive growing and oil production industry is strong. This industry has a long history and the olives grown here have high levels of biologically active compounds including a variety of phenolic compounds. Using residual materials generated by this industry in potential wood protection systems would not only valorise low-value materials and stimulate rural economies but would also provide an alternative to currently used oil-based protection systems. The objective of this study was to produce an oil treatment for wood protection and assess its efficacy in reducing leaching, weathering effects, and fungal decay. Two maleinisation techniques were used to chemically modify low-value lampante oil in an attempt to limit leaching when impregnated in wood. Pinus sylvestris (Scots pine) and Fagus sylvatica (European beech) were treated with the modified oils and underwent leaching, accelerated weathering, and decay tests. Leaching of the treatment oils was relatively low compared with other experiments and beech wood specimens treated with a direct maleinisation treatment showed improvement in performance compared to control specimens. In addition, it was found that the modified oils were not completely removed from the wood after solvent extraction indicating that they could potentially be used as an immobilisation agent in combination with other treatments thereby reducing the amount of active component of the protective agent.     

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.     

Boron effect on decay resistance of some fire-retardant coatings applied on plywood surface

Boron effect on decay resistance of some fire-retardant coatings applied on plywood surface was studied. Boric acid (B) was mixed into aqueous trimethylol melamine (TM) solution to increase the fixation in wood. To reveal the decay resistance of boric acid-added formulations, coatings were applied over radiata pine plywood surface as 100 g/m² amounts. Phosphoric acid (P) and dicyandiamide (D) were also used alone or in mixtures as reference coatings for comparison. Coated specimens were exposed to weathering according to Japanese Industrial Standard JIS A 9201 (1991) as severe leaching for 10 cycles, prior to decay-test. Non-leached and leached specimens, then, were inoculated with a brown-rot fungus Tyromyces palustris and a white-rot fungus Coriolus versicolor. Extent of the fungal attack was determined by mass loss of the specimens after 12 weeks incubation and microscopic examinations by 6 × magnification. Results indicated that TMB and TMDB coatings imparted the panels complete decay resistance despite severe weathering conditions and were proved superior over all other alone and mixture coatings. Although other combinations and alone treatments used in the study were also effective to inhibit the fungal damage before weathering, leaching greatly reduced their protective efficacy. Surface characteristics of decayed specimens were consistent with the determined values of mass losses caused by fungal attack. TMB and TMDB coatings were remarkably effective in maintaining sound surface properties after exposure to weathering and decay fungi.     

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.     

Effect of <Emphasis Type="Italic">Punica granatum</Emphasis> peel and <Emphasis Type="Italic">Melia azedarach</Emphasis> bark extracts on durability of European beech and maritime pine

A method to improve wood durability using natural extracts was evaluated. Wood deterioration is a condition caused by several abiotic and biotic factors including fungal contamination. To date, approaches aiming at the reduction of these contaminants mainly involve the use of chemicals agents. Natural products could represent an alternative strategy. Aqueous extracts of Punica granatum L. (pomegranate) peel and Melia azedarach L. barks were evaluated as antifungal agents to improve natural durability of beech wood and maritime pine. To evaluate the effect of treatments under simulated accelerated ageing of wood by natural conditions, impregnation and leaching tests were performed. Results demonstrated that samples impregnated with pomegranate or M. azedarach solutions notably increased the biological resistance of wood in a dose-dependent manner. These results were confirmed by the reduction in weight losses in treated samples even after 6 weeks of fungal exposure. Moreover, after leaching tests, 20 and 7% (w/v) of pomegranate and M. azedarach extract solutions were demonstrated as the better concentrations to enhance wood durability. Total phenol content and characterization of the phenolic compounds in both, natural extracts and wood samples were analyzed by Folin–Ciocalteu assay and HPLC-DAD. In conclusion, it was demonstrated that the present method can be considered as an effective treatment to increase wood durability while it proposes the valorization of natural extractives in wood industry.     

Prediction of non-recoverable collapse in Eucalyptus globulus from near infrared scanning of radial wood samples

Near infrared (NIR) spectroscopy calibrations was used to predict radial profiles of cellulose content, wood density, cellulose microfibril angle (MFA) and modulus of elasticity (MOE) in 20-year-old plantation Eucalyptus globulus to identify non-recoverable collapse zones associated with tension wood. Radial (cambium-to-pith) wood cores were extracted at a height of 1.0 m from trees selected to represent a range of silvicultural treatments. NIR spectra were measured at 1 mm intervals along the radial-longitudinal face of each core after drying to 12 % equilibrium moisture content (EMC) at 40 °C. Tangential shrinkage was measured at eight points along each core, following steam reconditioning and re-drying to 12 % EMC. Additional cores from 20 of the sample trees were collected. Radial profiles of density, MFA and MOE were obtained for wood strips prepared from these cores, using the SilviScan 3 wood assessment system. Trait profiles were matched to radial NIR scans of these cores, enabling the development of NIR calibrations using partial least squares (PLS) regression. These, and an existing NIR calibration for cellulose content, were used to predict the radial profiles of the four wood properties for the first set of cores. Predicted wood properties were then related to actual tangential shrinkage measurements and the occurrence of visible bands of non-recoverable collapse. A regression model was developed to reliably predict regions of non-recoverable collapse from NIR-predicted cellulose content and MOE. Micrography of stained wood sections indicated that the collapse was caused by the presence of tension wood.