Copper-based Wood Preservatives Research Articles

The effect of soil type on copper leaching from wood treated with three copper-based wood preservatives

ABSTRACT In this study, Scots pine (Pinus sylvestris L.) wood samples were treated with 3 different major wood preservatives (alkaline copper quaternary (ACQ), copper chrome boron (CCB) and copper azole (CuA)). Treated wood samples were subjected to 1 and 3 months of leaching in 3 different soil types and the amount of leached heavy metal Cu was determined on a laboratory scale. In addition, wood samples were exposed to white rot (Trametes versicolor) and brown rot (Neolentinus lepideus) fungi after leaching and weight losses were calculated. At the end of the 1 and 3 months of leaching period, the soil samples were taken from the pots and the amount of Cu was determined. The lowest Cu content (4.3 mg/kg) was detected in the samples treated with CCB among the wood preservatives, while the highest content (196.3 mg/kg) was determined in ACQ. The lowest Cu amount was determined in loamy sand soil type and the highest Cu amount was determined in clay loam soil type. According to the findings from the current study, leaching in soil did not affect weight losses caused by T. versicolor, while significant weight losses occurred by N. lepideus. This study indicated that loamy sand soil is more suitable for the treated wood if there is a risk regarding leaching.

Combustion and Decay Resistance Performance of Scots Pine Treated with Boron and Copper Based Wood Preservatives

Boron compounds in the form of boric acid, borax or disodiumoctaborate tetrahydrate have been used as insecticide, fungicide and fire retardant in wood preservatives industry for decades. Also, copper is the most commonly used component in most of relatively modern preservatives as it is highly effective against fungi. The objective of this study was to investigate the combustion and decay resistance of boron-copper based solutions which were developed by our group. These solutions contain boric acid, sodium borate decahydrate, copper hydroxy carbonate, ethanolamine, quaternary ammonium compound (benzalkonium chloride), and/or organic acid (octanoic acid). Scots Pine (Pinus sylvestris) woods were treated with the preservatives according to ASTM D1413-07 standard by vacuum-pressure impregnation system, which was developed by our group. Decay resistance performances against white and brown rot fungi were determined according to EN 113 standard and combustion tests were performed with respect to ASTM E160-50 standard. All the impregnated wood samples were found highly resistant to both white (Trametes versicolor L.) and brown (Coniophora puteana L.) fungi. Besides, they gave better results than the control samples in terms of combustion tests.

Color change and surface chemistry of nano cerium-oxide treated wood after accelerated weathering

Doğal biyolojik polimer olan ahşap malzemenin, diğer yapı malzemelerine kıyasla önemli avantajları bulunmaktadır. Ancak ahşap malzeme, dış ortam koşullarında dayanıklı bir yapıya sahip olmadığı için mutlaka emprenye edilerek veya çeşitli üst yüzey işlemleri yapılarak kullanılmalıdır. Bu çalışmada, sarıçam (Pinus sylvestris L.) örnekleri %0,1; %0,2; %0,5; %0,7; %1; %2; %3; %4 ve %5 konsantrasyonda nano seryum oksit (CeO2) ile muamele edilmiş ve örneklerin hızlandırılmış yaşlandırma testi sonrasında renk değişimi ile yüzey kimyasındaki değişim araştırılmıştır. Hızlandırılmış yaşlandırma testine maruz bırakılan örneklerde başlangıçtan sonra 2, 4, 6, 8, 12, 16, 20, 24, 48, 72, 96, 120, 144 ve 168 saatte renk ve yüzey kimyasındaki değişim belirlenmiştir. Seryum oksidin etkinliği aynı konsantrasyon değerlerinde hazırlanan Tanalith-E çözeltisi ile muamele edilen örnekler ile kıyaslanmıştır. Böylece, seryum oksidin dış ortama maruz kalan ahşap malzemenin yüzey özelliklerinin iyileştirilmesinde, referans maddeye kıyasla kullanılabilirliği değerlendirilmiştir. Çalışma sonucunda, seryum oksit ve Tanalith-E ile muamele edilen örneklerde kontrol örneklerine kıyasla yüzey özellikleri korunmuştur. Araştırılan yüzey özelliklerindeki değişim en fazla, yaşlandırma testinin ilk saatlerinde gözlenmiş, seryum oksidin bakır bazlı emprenye maddesine (Tanalith-E) benzer sonuçlar verdiği bulunmuştur.

Peroxide Post-Treatment of Wood Impregnated with Micronized Basic Copper Carbonate

Wood is vulnerable to significant color changes when used in exterior applications. Some copper-based wood preservatives use colorants to minimize this color change. This paper examines the ability of a peroxide post-treatment to turn wood impregnated with micronized basic copper carbonate (CuCO3·Cu(OH)2) (MBCC) a stable brown color. MBCC-treated wood, with and without peroxide post-treatment, along with associated controls were evaluated for color change, erosion and black-stain fungal resistance after exposure to artificial photo-degradation. The impact of the peroxide treatment on copper leaching was assessed in a laboratory experiment, and the impact on copper reactivity was assessed by electron parametric resonance (EPR) spectroscopy. Peroxide post-treatment of wood pressure impregnated with MBCC was shown to reduce color change by more than 50% compared to controls. Erosion due to photo-degradation and colonization by black-stain fungi were lower in samples treated with MBCC than in untreated controls and were relatively unaffected by peroxide post-treatment. The peroxide post-treatment was associated with increased amounts of mobile copper. This led to increased susceptibility to leaching and to a more than 60% increase in the amount of copper than had reacted with the wood.

Shear strength in friction welded joint of poplar wood impregnated with copper-based wood preservative

Environmentally friendly processes are of great interest and considerably needed due to the worldwide problem of pollution. Linear vibration welding of timber structural elements provides new opportunities to potentially achieve structural joints. Mechanically induced vibrational wood fusion welding is shown to be due mostly to the melting and flowing of some amorphous, cells-interconnecting polymer material in the structure of wood, mainly lignin, but also hemicelluloses. In this study, poplar (Populus euramericana) samples were impregnated with alkaline copper quat (ACQ) in order to enhance welding performance. Chemical changes of the impregnated and welded specimens were characterized by FT-IR techniques. A decrease in the proportion of unoxidized phenolic groups in the lignin were observed by FT-IR and the decreased joint strength observed is impregnated wood. After impregnation, shear strength decreased by 37 % to 54 %. The X-ray CT-scanning results revealed that the average density of the poplar wood (368 kg/m3) increased to 710 kg/m3 by welding

Bio-based wood preservatives: Their efficiency, leaching and ecotoxicity compared to a commercial wood preservative

Companies in the wood industry are constantly developing their outdoor products. The possibility of using bio-based chemicals as an alternative to traditional wood preservatives—regulated in Europe by The Biocidal Products Regulation No 528/2012—has been considered, but chemical leaching from the wood decreases its effectiveness and may negatively affect the environment. This study aims to compare the effectiveness of bio-based chemicals with potential use in wood preservation to commercially available preservatives, to investigate their fixation to wood and their ecotoxicity and to quantify the potentially toxic elements leached from the wood. Pyrolysis distillates of tree bark, organic acids found in distillates, Colatan GT10 tannin extract and log soaking liquid as a hardwood veneer process residue were tested and compared with commercial pine oil and a copper-based wood preservative. In the wood decay test of impregnated pine sapwood specimens, Colatan GT10 extract performed as well as the commercial wood preservatives. The same decay trial with leached specimens significantly reduced the performance of the bio-based chemicals. The results of the ecotoxicity test with photoluminescent Aliivibrio fischeri bacteria showed that many bio-based chemicals with potential use in wood preservation have markedly lower ecotoxicity than commercially available wood preservatives, but the ecotoxicity of some bio-based chemicals is higher, as in the case of some of the pyrolysis distillates. The wood preservation efficiency and the ecotoxicity of the studied chemicals had a poor correlation, implying that other factors besides treatment agent toxicity play a role in deterring fungal growth on treated wood. The amount of elemental toxins in the leachates was low. These results emphasize the importance of the chemical ecotoxicity of bio-based preservative compounds, as their detrimental effect on the environment can be higher than that of the traditional preservatives unless effectively linked to wood to prevent leaching.

Durability and Mechanical Performance of Differently Treated Glulam Beams during Two Years of Outdoor Exposure

The performance of the composites is influenced by the service life of input raw wood material and used adhesives. The aim of the study was to assess the durability and mechanical performance of glulam beams treated in a different way (thermally modified and/or treated with copper-based wood preservative) and exposed in an outdoor application. Glulam beams (83 mm × 68 mm × 1100 mm), made of three layers of Norway spruce (Picea abies) with PUR adhesives used have been exposed in use class 3.2 in a horizontal position since 4th November 2016. Part of the specimens was equipped with MC sensors. Every year, the degradation was evaluated visually. The dynamic modulus of elasticity was determined by longitudinal vibration, and the static modulus of elasticity using a 4-point bending test. On the smaller specimens, cut from glulams, compressive strength, delamination, and shear strength of adhesive bonds were determined. After two years of exposure, the results indicate that the performance of glulams is determined by the wood modification and applied wood preservative.

Revalorization of coffee silverskin as a potential feedstock for antifungal chemicals in wood preservation

The possibility of using coffee silverskin, an industrial waste from the coffee roasting process, as an antifungal feedstock in wood preservative formulations was investigated. Silverskin hot water extract and its antifungal properties in vitro against Rhodonia (Poria) placenta, Gloeophyllum trabeum, and Trametes versicolor were characterized, and its in vitro effects on wood decay caused by Coniophora puteana were analyzed. A kinetic luminescent bacteria test was performed using Aliivibrio fischeri to measure the acute ecotoxicity of the silverskin extracts. The antifungal test showed 60–70% growth inhibition of the studied fungi at higher concentrations—3%—but did not meet the high inhibition—100%—of the commercial wood preservative. The phenolic compounds, such as chlorogenic acid and its derivatives, and caffeine derivatives, were the main constituents of the silverskin extracts and considered the responsible compounds of the fungal inhibition. The silverskin extracts were significantly less toxic than the commercial copper-based wood preservative. Revalorization of silverskin from industrial residues does not perform as a wood preservative but it remains a potential source of antifungal chemicals for wood preservative formulations.

Quantitative human health risk assessment along the lifecycle of nano-scale copper-based wood preservatives

The use of nano-scale copper oxide (CuO) and basic copper carbonate (Cu2(OH)2CO3) in both ionic and micronized wood preservatives has raised concerns about the potential of these substances to cause adverse humans health effects. To address these concerns, we performed quantitative (probabilistic) human health risk assessment (HHRA) along the lifecycles of these formulations used in antibacterial and antifungal wood coatings and impregnations by means of the EU FP7 SUN project’s Decision Support System (SUNDS, www.sunds.gd). The results from the risk analysis revealed inhalation risks from CuO in exposure scenarios involving workers handling dry powders and performing sanding operations as well as potential ingestion risks for children exposed to nano Cu2(OH)2CO3 in a scenario involving hand-to-mouth transfer of the substance released from impregnated wood. There are, however, substantial uncertainties in these results, so some of the identified risks may stem from the safety margin of extrapolation to fill data gaps and might be resolved by additional testing. Our stochastic approach successfully communicated the contribution of different sources of uncertainty in the risk assessment. The main source of uncertainty was the extrapolation from short to long-term exposure, which was necessary due to the lack of (sub)chronic in vivo studies with CuO and Cu2(OH)2CO3. Considerable uncertainties also stemmed from the use of default inter- and intra-species extrapolation factors.

GENE EXPRESSION ANALYSIS OF WOOD DECAY FUNGUS FIBROPORIA RADICULOSA GROWN IN ACQ-TREATED WOOD

Copper-tolerant brown-rot fungi are able to degrade wood treated with copper or copper-based wood preservatives. This research used quantitative reverse transcriptase polymerase chain reaction to explore what genes of the brown-rot fungus, Fibroporia radiculosa, were expressed when the fungus was overcoming the wood preservatives and decaying the wood. Aryl alcohol oxidase, catalase, oxalate decarboxylase 2, and copper resistance P-type ATPase pump had higher expression on alkaline copper quat type D treated wood compared with week 1. In addition, two genes had high expression at week 5; glycoside hydrolase 5 and glycoside hydrolase 10 when wood strength loss was around 50%. Glyoxylate dehydrogenase had high expression until week 8. This gene might be involved in the production of oxalate. Laccase, oxalate decarboxylase 1 and isocitrate lyase were not differentially expressed, suggesting that these genes were not involved in the decay process of alkaline copper quat-treated wood. These results are important to understand the genes that are involved in the mechanism of copper tolerance and wood decay in F. radiculosa.

Quality of Copper Impregnated Wood in Slovenian Hardware Stores

Ten different samples from Slovenian hardware stores were analysed. Samples were treated with copper based wood preservatives that were designed and advertised to be used in heavy duty applications in ground (use classes 4) and above ground (use classes 3.2). Retention and fungicidal properties were determined in order to establish the quality of treatment quality. Retention was determined by XRF analysis, while a modifi ed EN 113 procedure was applied for the assessment of fungicidal properties. Two brown rot fungal species, Gloeophyllum trabeum and Fibroporia vaillantii, were used for durability testing. The results of the analysis clearly showed that only three of the inspected wood products met penetration requirements, and none of them had sufficient retention, which is also reflected in insufficient durability against wood decay fungi.

Mycoremediation of copper: Exploring the metal tolerance of brown rot fungi

In recent decades, fungal roles in bioremediation of toxic contaminants such as potentially toxic elements (PTEs) residing in soil, waste water, and landfills have been studied. Bioremediation is an alternative way to deal with toxic contaminants in the environment. Some decay fungi are able to remove metals by producing metabolites, such as oxalate, which can react with metal ions and generate insoluble forms of metal:crystal complexes. Brown-rot fungi have the ability to produce extracellular oxalate in significant amounts, and this is closely related to chelation of copper by precipitating to copper oxalate crystals. Copper-tolerant brown-rot fungi have a potential role in a bioremediation system by depolymerizing the structure of wood treated with copper-based wood preservatives and adapting to copper through increased oxalate production and formation of copper oxalate crystals. The focus of this review is to suggest that copper-tolerant brown-rot fungi could be a viable option for use in future mycoremediation practices.

Performance of copper treated utility poles and posts used in service for several years

Copper based wood preservatives are among the most important wood preservatives for heavy-duty applications. Wood treated with copper-based preservatives performs excellently if applied according to preservative specifications. If used improperly, premature failures can appear. In order to elucidate the properties of copper treated wood in use, utility poles and posts treated with copper-based preservatives were investigated. Poles were cut into smaller specimens, and copper and chromium penetration, retention, mechanical properties, extractive content, short-term water uptake and fungicidal properties were then determined. The results clearly showed that wood retains its properties if treated with sufficient amounts of copper-based wood preservatives. Insufficient amounts of preservatives applied result in premature failures of wood commodities. Regardless of the type of wood preservative used, the central part of spruce wood poles and piles is the weakest point, where the majority of the failures occurs.

Surface properties of bamboo and Scots pine impregnated with boron and copper based wood preservatives after accelerated weathering

In this study, we investigated the color, gloss and surface roughness of bamboo (Phyllostachys bambusoides) and Scots pine (Pinus sylvestris) samples impregnated with boron and copper based preservatives during accelerated weathering from 168 h to 672 h. Tanalith-E, ACQ, wolmanit-CB were used as copper-based chemicals, while a mixture of boric acid and borax (7:3; w/w) was used as the boron compound. Results showed that retention values of bamboo samples were lower than the retention values of Scots pine samples probably due to the bamboo’s anatomical structure and penetration characteristic. Bamboo surfaces became rougher and darker after impregnation and accelerated weathering compared to initial surfaces. Longer accelerated weathering periods seemed to have not a considerable effect on surface roughness of bamboo samples impregnated with copper based preservatives. Gloss of impregnated Scots pine samples increased with longer accelerated weathering period while gloss of bamboo samples decreased slightly with longer accelerated weathering period. Wolmanit-CB seemed to be most effective wood preservative for hindering color change and ensuring smooth surfaces after accelerated weathering. Color changes caused by accelerated weathering tended to be greater for impregnated bamboo samples than impregnated Scots pine samples.

The effect of plasma treatment on mechanical properties, surface roughness and durability of plywood treated with copper-based wood preservatives

The effect of plasma treatment on strength properties of wood-based composites was studied. Veneers were obtained from beech logs (Fagus orientalis L.) and treated with 3 % of Tanalith E and Celcure AC-500. Two types of gasses (O2 and N2) were tested for plasma treatment. The effect of plasma treatment on bonding shear strength, bending strength and modulus of elasticity of plywood panels were determined according to EN 314-1 and EN 310, respectively. Surface roughness, leaching, decay test against white (Trametes versicolor) and brown rot [Postia placenta (FPRL 280)] and ground contact test of plywood samples were evaluated after plasma treatment. Results showed that plasma treatment with O2 increased the bonding strength of plywood compared to control and treated groups. However, plasma treatment slightly increased the mass losses caused by white rot, but decreased mass losses caused by brown rot in some groups. Regarding leaching test, plasma treatment slightly increased the leaching rate of copper in some groups. Ground contact test revealed that there was no delamination in bonding line on the plasma-treated samples.

Bamboo (Bambusa vulgaris Schrad.) from Moist Forest and Derived Savanna Locations in South West Nigeria – Properties and Gluability

Bamboo culms of Bambusa vulgaris Schrad. were collected from two locations in moist forests and two sites in derived Savanna zones in South West Nigeria. The study involved chemical analyses, density variability, bonding tests, gluability tests, and measurements of bending strength of the bamboo in addition to durability testing with decay fungi and treatability of glued boards with a copper-based wood preservative. Chemical analyses showed a uniform composition of the bamboo with a cellulose content of 45 to 47.5% and a lignin content of 23 to 25.6% as the predominant chemical constituents. An average wood density of 700 kg/m(3) was a prerequisite for high mechanical strength. The moduli of elasticity were high and exceeded 14 kN/mm(2) for bamboo boards and 13 kN/mm(2) for finger joints. Bamboo boards from all growth sites showed high moduli of rupture in the range of 150 to 166 N/mm(2) and 72.9 to 94.7 N/mm(2) for boards and finger joints, respectively. Bamboo from the four sites showed variable mass loss with the EN-113 (1996) test method, which classifies this biomass as a moderately to non-durable plant material. White rot fungus (Trametes versicolor) caused the highest mass losses (11.2 to 16.8%). The bamboo showed good treatability using a 500-kg/m(3) solution of a copper-based preservative.

Leaching and decay resistance of alder and pine wood treated with copper based wood preservatives

The objective of this study was to determine the leaching and decay resistance of Alder (Alnus glutinosa subsp. barbata) and Scots pine (Pinus sylvestris) wood samples treated with copper based preservatives. Samples were treated with CCA, ACQ, Tanalith E and Wolmanit with different concentrations. Scots pine samples were exposed the mini-block test against brown rot fungi (Poria placenta) and Coniophora puteana while alder wood samples were tested against brown rot fungi (Coniophora puteana) and white rot fungi (Coriolus versicolor). Regarding to leaching test, treated samples were impregnated with 300 ml of distilled water and after 6, 24, 48 and thereafter at 48-hour intervals, the leachate was removed and replaced with fresh distilled water according to AWPA E11. Samples of each leachate were collected and retained for copper analysis. Amount of copper released from treated wood during the leaching test was chemically analyzed with Atomic Absorption spectroscopy. Perchloric acid procedure for the digestion of wood was used according to AWPA A7-97. The amount of copper component (Qd), the cumulative quantities leached (Qc) and the average daily fluxes (FLUX) were calculated. Results shows that CCA treated samples release less copper compared to other copper based preservatives used in this study. Highest mass losses were obtained from the leached samples treated with 1% of ACQ-2200 against decay fungi.

옥외 내구성 향상을 위한 목재보존제의 최근 연구 동향 -비 구리계 약제를 중심으로-

본 연구에서는 목재보존제의 최근 국제적 동향 중, 비 구리계 약제를 중심으로 조사되었다. 최근의 목재보존제 연구 분야에서 다루어지는 비 구리계 약제로는 환경친화적 수용성약제 성분의 대표적인 붕소계 화합물이 가장 많았고, 자연에서 얻어지는 천연물질을 이용한 약제, 화학처리목재, pyrethroid계 방충제 등이 포함되었다. 인축 및 환경에 대한 사용안전성이 고려된 약제들이 주 연구대상이 되는 경향이 있었다. 붕소의 경우에는 옥외 사용 시 물에 대한 용탈성을 개선하기 위하여 다양한 고분자 등의 물질을 도입하여 정착성을 높이고자 하는 연구들이 주요 이슈였다. 또한 의학 분야에서 많이 다루어지던 천연물질이 목재보존제로써 사용하고자 하는 시도와 치수안정성을 목적으로 개발되었던 아세틸화 목재와 같은 화학수식목재에 대한 옥외 사용 시도가 눈에 띄게 증가된 경향을 나타내었다. Current research trends of non-copper wood preservatives for enhancing durability was reviewed; as a follow-up of the review in 2012 on copper-based wood preservatives. Main environmental friendly non-copper wood preservatives studied by many scientists were boron-based compounds, synthetic compounds from natural products, and pyrethroids family of chemicals, etc. The critical issue regarding treated woods with boron-based compounds used outdoors was the leaching of boron. Many studies mainly focused on boron fixation improvement using variety of polymers. Moreover, the studies showed notable increases in attempts to use natural products used commonly in the medical fields as wood preservatives as well as outdoor use of chemical modified such as acetylated wood developed in purpose of stabilizing dimension.

옥외 내구성 향상을 위한 목재보존제의 최근 연구 동향 - 구리 기반 약제를 중심으로 -

Current research trends of non-copper wood preservatives for enhancing durability was re- viewed; as a follow-up of the review in 2012 on copper-based wood preservatives. Main environ- mental friendly non-copper wood preservatives studied by many scientists were boron-based compounds, synthetic compounds from natural products, and pyrethroids family of chemicals, etc.

Bioavailability and form of copper in wood treated with copper-based preservative

The biological performance of copper-treated wood is related to the amount and form of copper available in treated wood. The amount of copper biologically available in wood treated with copper-based wood preservatives such as micronized copper azole, micronized copper quat, alkaline copper quat, copper chrome arsenic and copper azole was estimated by using non-sequential chemical extraction method. DI water, KNO3, KF, Na4P2O7, EDTA disodium salt and HNO3 solutions were used to extract copper from treated wood in an ultrasonic bath. The extracts and water washings were collected, centrifuged and analyzed to determine the amount of copper. High amount of copper was extracted with EDTA disodium salt and HNO3 solutions followed by sodium pyrophosphate, while that extracted with KNO3, KF and DI water was low. EDTA disodium salt and sodium pyrophosphate are known as good complexing/chelating agents, capable of chemically reacting with copper in treated wood, to form water-soluble copper salts. HNO3 was capable of extracting almost 100% of copper from copper-treated wood because of its low pH capable of solubilizing solid, unfixed and fixed copper in wood. KNO3 reacted with exchangeable form of copper, while KF is responsible for the extraction of physically adsorbed copper. DI water mostly removed soluble form of copper from treated wood. The amount of copper bioavailability from copper-treated wood can be estimated by the amount of copper extracted using DI water, KNO3 and KF solutions under given environmental conditions. The amount of bioavailable copper extracted from micronized copper–treated wood using DI water, KNO3 and KF solutions, although found to be low as compared with that extracted from ACQ, CCA and CA wood, was sufficient to prevent the growth of wood-destroying fungi.