Durability test of bamboo against fungi according to EN standards

The durability of five bamboo species from various origin against brown-, white- and soft-rot fungi was investigated in Kolle flasks in accordance with the European standards EN 350-1, EN 350-2 and EN 113. Considerable variability exists in the durability of the bamboo species. Guadua angustifolia was rather resistant to Trametes versicolor and Dendrocalamus asper against Chaetomium globosum. Among the brown-rot fungi, the four strains of Coniophora puteana and two strains of Gloeophyllum trabeum produced low mass loss (maximum 2.9 %). Of the white-rot fungi, T. versicolor yielded the highest decay (max. 15.3 %), whereas Schizophyllum commune was rather inactive (max. 3.2 %). Of the soft-rot fungi, Ch. globosum showed medium degradation (max. 9.6 %) and Paecilomyces variotii low decay (max. 3.1 %).     

A comparative study on brown-rot fungus decay and subterranean termite resistance of thermally-modified and ACQ-C-treated wood

The resistance of thermally-modified and Alkaline Copper Quaternary type C (ACQ-C) treated aspen (Populus tremuloides Michx), jack pine (Pinus banksiana Lamb.), yellow-poplar (Liriodendron tulipifera L.), and Scots pine (Pinus sylvestris L.) against the brown-rot fungus (Gloeophyllum trabeum) and Eastern U.S. subterranean termite (Reticulitermes flavipes) was studied. Wood materials were thermally-modified at a temperature of 210 °C for 15 min. ACQ-C was impregnated into yellow-poplar and jack pine wood at three different retention levels and at each level both leaching and non-leaching procedures were conducted. Results indicate that ACQ-C-treated yellow-poplar and jack pine became significantly more resistant to the brown-rot fungus compared to the thermally-modified wood and the untreated control. Thermally-modified yellow-poplar and jack pine were more resistant to this fungus than untreated wood. For aspen and Scots pine, the resistance to G. trabeum was improved after the thermal modification, but it remained susceptible to this brown-rot fungus decay. Termite susceptibility of thermally-modified aspen, jack pine, and yellow-poplar was comparable to that of untreated controls. Significantly greater termite attack occurred on thermally-modified Scots pine wood than it did on untreated wood. This likely is attributed to some compounds contained in Scots pine wood that inhibited termite attack.     

Chemical extractive compounds determining the brown-rot decay resistance of teak wood

The relative importance of extractive content and its chemical compounds in imparting brown-rot decay resistance of teak wood was determined using HPTLC. Total extractive content (12.44%), tectoquinone (0.23%) and naphthoquinone (0.62%) were lower in home garden teak of wet site than of dry site with corresponding values of 15.98%, 0.34% and 1.26% in the latter. The amount of napthoquinone was more consistently correlated with higher decay resistance from the wet to the dry and planted sites implying that napthoquinone is the single most important compound which imparted decay resistance to teak wood against the two brown-rot fungi, viz. Polyporous palustris and Gloeophyllum trabeum.     

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.     

Feasibility study of utilization of commercially available polyurethane resins to develop non-biocidal wood preservation treatments

Evaluation of commercially available polyurethane resins used up to now for coating applications to develop non-biocidal wood preservation treatments has been conducted. A simple method of vacuum impregnation of these resins into beech wood (Fagus sylvatica L.) and pine wood (Pinus sylvestris L.) samples followed by varied curing processes at ambient temperature, 103, and 200 °C has been performed. Based on the analysis of weight percent gain before and after leaching, treatment resistance to leaching, anti-swelling efficiency, wettability and decay durability measured for treated and untreated blocks after leaching with the white-rot fungus Coriolus versicolor for both wood species and the brown-rot fungi Poria placenta and Gloeophyllum trabeum for pine wood, it can be concluded that such treatment can be considered as potential valuable non-biocidal treatments.     

Influence of fungal decay by different basidiomycetes on the structural integrity of Norway spruce wood

The potential influence of diverse decay patterns caused by different brown rot causing basidiomycetes on the structural integrity of wood was investigated. Therefore, decayed Norway spruce (Picea abies Karst.) specimens representing a wide range of mass loss, caused by four different brown-rot fungi and one white-rot fungus, were applied to a high-energy multiple impact (HEMI)-test series. The relationship between the resistance to impact milling (RIM) and the mass loss by fungal decay could be subdivided into three areas: 1. Prior to measurable mass loss, a strength reduction was detectable due to the depolymerisation of wood cell wall components. 2. Between 0 and 25–30% mass loss, RIM decreased with increasing mass loss. 3. Above 30% mass loss, RIM increased again due to gluing effects of the fungal mycelium. The influence of the different brown rot fungi on the structural integrity of the wood differed slightly, but partly significantly.     

Resistance of thermally modified ash (<Emphasis Type="Italic">Fraxinus excelsior</Emphasis> L.) wood under steam pressure against rot fungi,soil-inhabiting micro-organisms and termites

Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood^® treatment intensity on improvement of wood decay resistance against soil-inhabiting micro-organisms, brown/white rots and termite exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170, 200, 215 and 228 °C. The reference materials were untreated ash and beech wood for decay resistance tests, untreated ash wood for soil bed tests and untreated ash, beech and pine wood for termite resistance tests. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungi according to CEN/TS 15083-1 directives. Durability against soil-inhabiting micro-organisms was determined following the CEN/TS 15083-2 directives, by measuring the weight loss, modulus of elasticity (MOE) and modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis species was used for determining the termite attack resistance by non-choice screening tests, with a size sample adjustment according to EN 117 standard directives on control samples and on samples which have previously been exposed to soil bed test. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature above 215 °C, represented by a wood mass loss (ML%) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ‘‘durable’’ or ‘‘very durable’’ in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever the heat treatment conditions are, thermally modified ash wood was not efficient against termite attack neither before nor after soft rot degradation.     

Efficacy of novel organotin(IV) complexes on non-durable tropical wood against decay fungi

Interest in organotin(IV) compounds is increasing due to their interesting structural features and possession of biological activities. The objective of this study was to determine the efficacy of novel organotin(IV) complexes against Trametes versicolor and Gloeophyllum trabeum decay fungi. Soil block decay test was performed using T. versicolor and G. trabeum for 16 weeks. Ten 19 × 19 × 19 mm³ sized wood cubes of Alstonia scholaris, Macaranga triloba and Hevea brasiliensis were treated with three levels of concentration (0.1, 0.5 and 1 %) of monomethyltin(IV) (MMT) and monophenyltin(IV) (MPT) of monosubstituted organotin(IV) and dimethyltin(IV) (DMT), diphenyltin(IV) (DPT) and dibutyltin(IV) (DBT) of disubstituted organotin(IV) complexes with 2-acetylpyridine-N(4)-cyclohexyl thiosemicarbazone (APCT) ligand and their respective retention uptake was determined. The best protection against decay fungi was provided by dibutyltin(IV) complex followed by diphenyltin(IV), dimethyltin(IV), monophenyltin(IV) and monomethyltin(IV) complexes with mean weight loss ranging from 4 to 5, 5 to 7, 8 to 9, 10 to 11 and 14 to 19 percent, respectively while the weight loss of the untreated wood cubes varied from 51 to 65 %. Wood densities decreased with increased weight loss. Density reduction of monosubstituted organotin(IV) treated wood cubes was higher than disubstituted organotin(IV) treated wood cubes. Soil block test showed that selected organotin(IV) complexes are effective and among all of them dibutyltin(APCT) complex gave the best protection against the tested T. versicolor and G. trabeum decay fungi.     

Changes of the pH value of impregnated wood during exposure to wood-rotting fungi

and Schizophyllum commune). The third species was the brown-rot fungi Antrodia vaillantii, using three different strains of this species. Antrodia vaillantii substantially decreased the pH-value of impregnated and unimpregnated wood before any mass loss appeared. On the other hand, the white-rot fungus T. versicolor and S. commune caused a slight increase of the pH of impregnated and unimpregnated wood. It is suggested that a decrease of pH of wood may indicate early stages of decay by brown rot fungi.     

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.     

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.     

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.     

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.     

Improvement of fungicidal properties and copper fixation of copper-ethanolamine wood preservatives using octanoic acid and boron compounds

Copper ethanolamine preservatives are one of the most important solutions for wood preservation. As copper itself can not ensure sufficient protection against wood destroying organisms we combine it with other co-biocides like quaternary ammonium compounds, azoles and/or boron. Influence of different boron compounds and octanoic acid on copper fixation as well as performance of spruce wood impregnated with different copper/ethanolamine/boron based aqueous solutions is described in this paper. Copper fixation was determined according to the modified ENV 1250 (1994) standard method, while performance against Antrodia vaillantii, Gloeophyllum trabeum and Trametes versicolor was tested according to the mini block procedure. The results showed that addition of boron increases copper leaching, but on the contrary improves performance against wood decay fungi. On the other hand, addition of octanoic acid improves copper fixation, and slightly decreases resistance against copper tolerant fungi.     

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.     

Surface treatment for preventing decay and termite attack in wood using didecyl dimethyl ammonium tetrafluoroborate (DBF) incorporated with acryl-silicon type resin

Surface treatment of wood was carried out using acryl-silicon type resin including didecyl dimethyl ammonium tetrafluoroborate (DBF), boron-containing quaternary ammonia compound. Surface-treated wood specimens were exposed laboratory decay resistance tests after completing a 10-cyle severe weathering process. In laboratory decay resistance tests, one brown-rot decay fungus, Fomitopsis palustris and one white-rot decay fungus, Trametes versicolor were used. The specimens were also subjected to laboratory termite resistance tests using subterranean termites, Coptotermes formosanus. Wood specimens treated with 2% DBF and resin containing preservative solution showed improved decay and termite resistance suggesting that the preservative solution at 2% DBF concentration provides lasting protection against wood degradation owing to the amount of DBF remaining in the wood after severe weathering process. However field tests are needed to determine the performance of surface-treated wood with DBF and the acryl-silicon type resin in more realistic conditions.     

Mechanical behaviour of Québec wood species heat-treated using ThermoWood process

Finnish wood heat treatment technology, ThermoWood, was recently introduced to Québec, Canada by Ohlin Thermo Tech. Subsequently, a large number of initial trials were conducted on five commercially important Québec wood species, spruce (Picea spp.), pine (Pinus spp.), fir (Abies spp.), aspen (Populus spp.), and birch (Betula spp.). These species were thermally-modified in different batches at temperatures of 200 °C or higher. The static bending and hardness of the thermally-modified wood were examined. Decreases of 0% to 49% were observed in modulus of rupture of heat-treated spruce, pine, fir, and aspen depending on species and treatment schedules used; modulus of rupture of birch increased slightly after the heat treatment. The decrease in modulus of elasticity of heat-treated spruce and pine ranged from 4% to 28%; but the modulus of elasticity of heat-treated fir, aspen, and birch increased except one trial for fir. Hardness of the heat-treated wood increased or decreased depending on the species, test directions (radial, tangential, and longitudinal), and treatment schedules.     

Changes of the pH value of impregnated wood during exposure to wood-rotting fungi

Trametes versicolor and Schizophyllum commune). The third species was the brown-rot fungi Antrodia vaillantii, using three different strains of this species. Antrodia vaillantii substantially decreased the pH-value of impregnated and unimpregnated wood before any mass loss appeared. On the other hand, the white-rot fungus T. versicolor and S. commune caused a slight increase of the pH of impregnated and unimpregnated wood. It is suggested that a decrease of pH of wood may indicate early stages of decay by brown rot fungi.

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Trametes versicolor und Schizophyllum commune). Die dritte Art war vom Braunf?uletyp (Antrodia vaillantii), wovon drei verschiedene St?mme eingesetzt wurden. Antrodia vaillantii senkte den pH deutlich in impr?gnierten und unbehandelten Proben, noch bevor ein Massenverlust auftrat. Die beiden Weissf?uleerreger T. versicolor und Sch. commune lie?en den pH dagegen ansteigen. Anhand des pH-Abfalls konnte man schon frühe Stadien eines Braunf?uleabbaus erkennen.

     

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.     

Correlation between brown rot decay and Pilodyn measurements

Assessment of brown rot decay is one of the most important issues within remedial treatment of attacked wood constructions. Pilodyn is a well-established tool for the assessment of density of several commercially important plantation species, therefore the authors were interested in its suitability to evaluate rate of decay as well. The Pilodyn measurements performed on Norway spruce wood exposed to several brown rot fungi clearly indicate correlations between needle penetration and mass loss.