Erik Larnøy
Forsker
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Gry Alfredsen Erik Larnøy Greeley Beck Johan Bjørnstad Lone Ross Gobakken Callum Aidan Stephen Hill Andreas TreuSammendrag
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There is a need for new solutions in wood protection against marine wood borers and termites in Europe. A new solution could be the esterification of wood with sorbitol and citric acid (SCA) since these are inexpensive and readily available feedstock chemicals and have shown protective properties against fungal wood degradation in earlier studies and prevented macrobiological degradation, as shown in this study. Protection of wood products in the marine environment lacks available wood preservatives that are approved for marine applications. Termite infestation is opposed mainly by biocide treatments of wood. Several wood modification systems show high resistance against both marine borers and subterranean termites. However, the existing commercialized wood modification products are costly. Both macrobiological forms of degradation represent a great threat for most European wood species, which are rapidly and severely degraded if not properly treated. This study investigated esterified wood in standard field trials against marine wood borers, and against subterranean termites in laboratory trials in a no-choice and choice test. The treatment showed good resistance against wood borers in the marine environment after one season and against subterranean termites in the laboratory after eight weeks. The low termite survival rate (SR) in the no-choice test during the first week of testing indicates a mode of action that is incomparable to other wood modification treatments.
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Forfattere
Andreas Treu Katrin Zimmer Christian Brischke Erik Larnøy Lone Ross Gobakken Foued Aloui Simon M. Cragg Per-Otto Flæte Miha Humar Mats Westin Luisa Borges John WilliamsSammendrag
Timber structures in marine applications are often exposed to severe degradation conditions caused by mechanical loads and wood-degrading organisms. This paper presents the use of timber in marine environments in Europe from a wood protection perspective. It discusses the use of wood in coastline protection and archeological marine wood, reviews the marine borer taxa in European waters, and gives an overview of potential solutions for protection of timber in marine environments. Information was compiled from the most relevant literature sources with an emphasis on new wood protection methods; the need for research and potential solutions are discussed. Traditionally, timber has been extensively utilized in a variety of marine applications. Although there is a strong need for developing new protection systems for timber in marine applications, the research in this field has been scarce for many years. New attempts to protect timber used in marine environments in Europe have mainly focused on wood modification and the use of mechanical barriers to prevent colonization of marine wood borers. The importance of understanding the mechanisms of settlement, migration, boring, and digestion of the degrading organisms is key for developing effective systems for protecting timber in marine environments.
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In built environments the combustibility of wood is a great concern, which limits the use of wood as a building material due to legislation. The reaction-to-fire properties of wood can be altered with the use of fire-retardant chemicals, and most of the commonly used fire retardants already have a long history of use. However, only limited information is available on the impact of different fire retardants on the adhesion properties of wood. Additionally, comparative studies between chemicals from different groups of fire retardants is scarce. The objective of this study was to investigate and compare the effects of two commonly used fire retardants, sodium silicate (SS) and diammonium phosphate (DAP), on veneer properties, the focus being especially on thermal behavior and adhesion. Thermal properties and combustibility were studied using thermogravimetric analysis (TGA), flame test and calorimetry. Glue bond strength was analyzed with an automated bonding evaluation system (ABES) and the leaching of chemicals was determined according to EN84. Additionally, the surface characteristics of modified veneers were imaged with scanning electron microscopy (SEM). Results revealed notable differences in the thermal properties of SS and DAP, with DAP having better fire-retardant performance in all thermal testing. SS also affected thermal properties and combustibility of modified veneers, but the effect was only moderate compared to DAP. Neither SS or DAP had any significant resistance against leaching but ABES testing showed a notable increase in the glue bond strength of DAP modified veneers.
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Finding efficient ways to decrease wood decay caused by fungi is an important issue in the timber construction. A possible way to avoid wood decay by fungi is by reducing the water content of wood, since water is a primary condition for fungal growth. Bulking of the wood cell wall by chemical reagents occupies the space where water normally occurs. This also improves the dimensional stability of the modified wood. The aim of the work was to react non-toxic reagents using a Maillard type of reaction in the wood cell wall. Wood was soaked in different aqueous solutions with a primary amine and a sugar as the main constituents. The wood was thereafter cured in an oven at 120°C. The preliminary results showed that the use of the Maillard reaction for wood modification is a promising method and is worth further research.
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It is recognised that flame retardant chemicals degrade and leach out of flame-protected wood claddings when exposed to natural weathering. However, the ability to survey the current state of a flame retardant treatment applied to a wood cladding, an arbitrary length of time after the initial application, is limited today. In this study, hyperspectral imaging in the near infrared to short-wavelength infrared region is used to quantify the amount of flame retardant present on wooden surfaces. Several sets of samples were treated with various concentrations of a flame retardant chemical and scanned with a push broom hyperspectral camera. An inductively coupled plasma (ICP) spectroscopy analysis of the outermost layer of the treated samples was then carried out in order to determine each sample’s phosphorus content, the active ingredient in the flame retardant. Spectra from the hyperspectral images were pre-processed with extended multiplicative scatter correction, and the phosphorus content was modelled using a partial least squares (PLS) regression model. The PLS regression yielded robust predictions of surface phosphorus content with a coefficient of determination, R2, between 0.8 and 0.9 on validation data regardless of whether the flame retardant chemical had been applied to the surface of the wood or pressure-impregnated into it. The result from the study indicates that spectral imaging around the 2400–2531nm wavelength region is favourable for quantifying the amount of phosphorus-based flame retardant contained in the outermost layer of non-coated wooden claddings. The results also reveal that the uptake of phosphorus-based flame retardant does not occur uniformly throughout the wood surface, but is to a larger extent concentrated in the earlywood regions than in the latewood.
Forfattere
Andreas Treu Katrin Zimmer Christian Brischke Erik Larnøy Lone Ross Gobakken Foued Aloui Simon M Cragg Per Otto Flæte Miha Humar Mats Westin Luisa M. S. Borges John WilliamsSammendrag
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The aim of this research is to determine if the polyesterification of sorbitol and citric acid in wood has a future potential as a wood modification process. Pine wood was impregnated with an aqueous solution containing citric acid and sorbitol and was thereafter cured at 103 or 140°C for 18 hours. The dimensional stability and leaching resistance were studied for both modification temperatures. The leachates from the modified wood samples were analysed by HPLC and the susceptibility to decay and staining fungi were studied. Impregnated samples cured at 140°C showed a permanent (leach-resistant) increased dimensional change, but samples treated at 103°C were not stable to leaching. Treated samples cured at 103 and 140°C showed significant resistance to white-rot (Trametes versicolor) and brown-rot decay (Postia placenta) after a leaching procedure. Furthermore, samples cured at 103 and 140°C (leached and unleached) were significantly less susceptible to blue-stain fungi than the untreated controls.
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Økt bruk av tre fører samtidig til flere restprodukter. Gjennom et nytt forskningsprosjekt vil NIBIO forsøke å finne ut hvordan restproduktene kan gjenvinnes og gjenbrukes flere ganger.
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Utstillingen «Det fantastiske treet» forteller om hvordan treet blir til, og at fotosyntesen er grunnlaget for alt liv. Bladene er verdens beste solfangere, og vi forteller hvordan fotosyntesen skjer i bladet. Trærnes magiske evne til å forvandle luft til sukker forklares på en ny og spennende måte. For å vise hvor spektakulær fotosyntesen er har vi lagd en 9 meter lang lysende akrylvegg som viser snittet av et blad. Midt i utstillingen står en 7,5 meter høy treskulptur laget av 10 km aluminiumsrør – selve Det fantastiske treet. Det fantastiske treeter et godt eksempel på forskningsformidling og et fruktbart samarbeid mellom to institusjoner. Norsk institutt for bioøkonomi (NIBIO) ved Skog og utmarksdivisjonen (tidligere Skog og landskap) har gjort et stort og omfattende arbeid med å tilgjengeliggjøre forskning og kvalitetssikre innholdet i utstillingen. NIBIO har vært en uvurdelig støttespiller i den faglige kvalitetssikringen. Vi har lagd en utstilling som skal overbevise publikum om hvilken spektakulær prosess fotosyntesen er og at det ikke er «bare bare» å bli et stort tre. Publikum skal både fascineres, og de skal få ny kunnskap. Den skal også vekke nysgjerrigheten for spennende forskning og alle ubesvarte spørsmål vi har rundt skogen og treet – det er fremdeles mye vi ikke vet!
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Wood protection against fungal decay is mainly based on chemical protection. Nontoxic protection methods have become more important in Europe due to environmental concerns. A method using electric fields to inhibit wood decay by fungi has been investigated in laboratory trials and wood mass loss and moisture content after exposure to fungal attack were determined. The results show significantly reduced mass loss for wood samples exposed to a low pulsed electric field (LPEF), while wood samples connected to alternating and direct current displayed higher mass loss compared to LPEF. Changing the electrode material reduced the mass increase due to metal ion transfer into the wood samples for LPEF-exposed samples. The use of conductive polymer instead of metal electrodes and carbon fibers was preferable as no ions were transferred and the integrity of the material persisted. Decay of pre-exposed wood samples to white rot could be stopped or slowed down by means of LPEF.
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The aim of this study was to determine the efficacy of chitosan and methoxysilane in the prevention of surface mold growth on rubberwood. Three different chitosan samples were tested; C1 (Mw 37 kDa), C2 (Mw 5.4 kDa) and C3 (Mw 3.5 kDa). Radial growth inhibition assay of the chitosan samples was investigated at concentrations ranging from 0.063 to 0.5 %w/v against Aspergillus niger BAM 4 and Penicillium decumbens CBS 121928. Chitosan samples C1 and C3 exhibited strong antifungal activity against both molds. Rubberwood samples were either vacuum or dip treated with varying concentrations of chitosan or silane solution. The content of chitosan in wood showed that after the leaching test, chitosan was well retained in both vacuum and dip treated wood. The concentration of silicon in wood showed similar results. The vacuum treated wood samples with chitosan C1 and C3 at 1 %w/v concentration had strong resistance against A. niger BAM 4. However, dip treated rubberwood samples with 2 %w/v chitosan solutions showed lower resistance against A. niger BAM 4. On the other hand, both vacuum and dip treated rubberwood samples with chitosan had no resistance against P. decumbens CBS 121928. The silane treated wood samples showed no resistance to fungal growth.
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Forfattere
Erik LarnøySammendrag
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Redaktører
Andreas TreuSammendrag
I Norge har vi en lang tradisjon for å bygge i tre. Fra vikingskip og stavkirker til moderne høyhus i massivtre: Treteknologisk kunnskap danner grunnlaget for estetisk og funksjonell bruk av tre som byggemateriale. Riktig bruk av trematerialer og treprodukter, fra et bærekraftig norsk skogbruk, er en forutsetning for lang levetid. Treprodukter med lang levetid er både klimavennlig og smart ressursbruk, det gir lengre karbonbinding, og kan erstatte andre materialer med negativ miljø- og klimaeffekt. Økt levetid på treprodukter får vi ved å utnytte den naturlige holdbarheten til utvalgte treslag, ved å unngå konstruksjonsmessige feil, og/ eller ved å behandle trevirket med en form for trebeskyttelse. I denne brosjyren presenterer vi de ulike typene trebehandling som finnes i Norge – både gamle og nye metoder. Med denne brosjyren ønsker vi å informere om riktig bruk av tre, og vi håper at brosjyren blir et godt hjelpemiddel til deg som er interessert i tre, som bygger med tre eller som på en eller annen måte arbeider med dette fantastiske materialet. Brosjyren «Trebehandling – Innovasjon, metoder og trender» er laget med støtte fra Landbruks- og matdepartement gjennom satsningen «Økt trebruk». Innholdet er basert på en serie artikler som har stått på trykk i magasinet SKOG.
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Når man bruker tre utendørs, i jordkontakt eller i innstallasjoner over bakken, vil trykkimpregnert trevirke beskytte mot sopp- og insektangrep og dermed øke trevirkets levetid. Impregnerte treprodukter til bruk som utvendig kledning, terrassedekk og gjerdestolper kan kjøpes i byggevarehandelen. Hva bør du som huseier vite når du kjøper og bruker impregnert tre?
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Tre er nå blitt så moderne og etterspurt at diskusjonen og de politiske avgjørelsene rundt bruken av tre stiller nye krav til forskere og krever høy rekruttering av studenter i fremtiden.
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I forrige utgave av SKOG beskrev vi tremodifisering ved bruk av furfurylering. En annen giftfri metode man kan bruke for å forbedre holdbarheten til tre, er acetylering.
Forfattere
Erik LarnøySammendrag
Det finnes flere ulike metoder og prosesser for varmebehandling av trevirke, også kalt termisk modifisering. Trevirket varmes opp til 160° C eller mer og under forhold med redusert oksygentilgang.
Forfattere
Erik LarnøySammendrag
En ny type produkter, hvor man blander trefiber med plastprodukter, kan erstatte ren plast eller aluminium på en rekke områder – for eksempel i bilindustrien.
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Wood for outdoor decking has a high market share in the Nordic and Baltic countries among private house owners. Important issues for the consumer are maintenance intervals and aesthetic appearance as well as decay resistance. Knowledge and consumer information about these aspects are required to ensure that wood can compete with alternative decking materials. In this paper an accelerated testing of decking, “stapelbädds metoden”, was evaluated after ten years of exposure at Ås, Norway. The test method covers different hazard situations within use class 3. Different preservatives and wood modification treatments were used in addition to untreated Scots pine (sapwood and heartwood) and larch (heartwood). The samples were treated with two different surface treatments. In addition there was one set without any surface treatment. Fungal discoloration and decay was evaluated. This provided new information about performance both on and above ground for a range of different combinations of preservative/modified systems and surface treatments of wood in decking for outdoor use. Generally, there were no significant differences in performance between the surface treatments, both with regard to surface discolouring fungi and decay fungi. For all surface treatments, the samples with rating 3 (heavy attack) in bottom layer in one or several stacks was: Tanalith M, Tanalith M (c), Gori Pres 10, Scanimp, styren, furfurylation, thermal modification, Ultrawood, larch heartwood, pine heartwood and pine sapwood. For all surface treatments, the samples with mean rating ≤ 2 (evident attack) in top and middle layer in one or several stacks was: ACQ 1900, Wolmanit CX 8, Tanalith E7, Gori SC 100, Royal, Royal with pigment, Scanimp, styrene and larch heartwood
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Bruke av tre som byggemateriale har en lang tradisjon i Norge. Det siste tiåret har vi fått strengere miljøkrav til trebeskyttelsessystemer. Samtidig ser man at nye designløsninger kan skape råteutfordringer i utendørs konstruksjoner. I denne artikkelen testes muligheten for å bruke antioksidanter for å hindre råtesopp i å bryte ned trevirket. Både naturlige antioksidanter fra norske bærsorter og syntetiske antioksidanter ble brukt. Alle prøvene hadde bra opptak av de ulike testløsningene, og alle viste en reduksjon i nedbrytning av trevirke sammenlignet med kontroll. Beskyttelsen virket generelt bedre mot brunråte enn hvitråte. De syntetiske antioksidantene stoppet nedbrytningen ved brunråte og bør vurderes som et additiv i eksisterende og andre trebeskyttelsessystemer for å oppnå økte synergieffekter.
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The use of wood in outdoor constructions has long traditions in Norway. In the last decade, the environmentally demands for wood protective systems has become stricter. At the same time, new design solutions are arising that will challenge the decay protection in outdoor constructions. In this article, the potential for antioxidants as a wood protective agent was tested. Both natural and synthetic antioxidants have been used. All samples achieved a sufficient uptake of impregnation agent, and all the tested products showed a reduction in wood decay rate compared to the control. The protections by the antioxidants are more effective against brown rot fungi, than white rot fungi. The synthetic antioxidants stop the fungal degradation of the brown rot fungi, and should be considered as an additive in future and existing wood protective systems.
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The aim of this study was to use energy-dispersive X-ray spectroscopy (EDX) to localize chitosan in the cell wall of chitosan-impregnated Scots pine. It was of interest to investigate the concentration of chitosan in wood to gain further knowledge and understanding of the distribution of chitosan in the wooden matrix. After deacetylation, chitosan was re-acetylated with chloroacetic anhydride to achieve a covalent bonding of chloride to the chitosan polymer. Chloride-labelled chitosan was measured by EDX using a scanning electron microscope and described as chloride intensity. Analysis of free chloride anions was performed by dialysis and inductively coupled plasma atomic emission spectroscopy. There was a significant correlation between the molecular weight of chitosan and the intensity of covalentbonded chloride to the chitosan polymer. High molecular weight chitosan showed a better interaction with the cell wall structure than low molecular chitosan.
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In Norway log buildings are normally produced from logs canted on two sides. The canted faces are prone to crack formation during drying. This can cause some disadvantages, e.g. the cracks can trap water from rainfall, because the canted faces form the wall surfaces in the log buildings.
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The objective of the study was to assess the influence of wood properties on copper leaching from wood treated with preservatives. Scots pine (Pinus sylvestris L.) trees were harvested from two different stands in Norway and one in Denmark. Sapwood was cut to samples (20 x 20 x 50 mm) in as many layers as the radial size allowed. Within this material, it is possible to trace the individual sample to its original position in the stem. Approximately half of the samples were treated with Wolmanit CX-8 and half with Tanalith. All samples were conditioned, impregnated with preservatives and leached according to EN84. Copper and boron content in water samples was determined by an ICP (Inductively Coupled Plasma) technique. The variation in leachability within trees, between trees and between different stands was studied. Statistical analyses showed that trees from the south are more prone to leaching and that samples from the lowest part of the tree fixate less preservative than those from the upper parts. In addition, drying method of the sample had an influence and differences were also noted between products used in the study.
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Wood protection in the last century has mainly been based on chemical treatments. Additionally, the type of construction of wooden buildings and the choice of wood species play an important role. Degradation of wood is not only caused by fungi or bacteria but also by insects. Termites have been a potential risk to wooden structures not only in the warmer regions of our continents but also beyond the regions of their natural habitat due to transport of wood. A new treatment, Electro osmotic pulsing technology (PLEOT), has been tested in lab termite tests and fungi tests. The two choice and non-choice termite tests were carried out using different duration of exposure and different initial wood moisture content. The results show growth of mould fungi on untreated wood samples with high initial wood moisture content after 4 weeks of termite testing whereas PLEOT treatment strongly reduced the development of moulds. Termite mortality was high on untreated wood samples with high initial moisture content but not on wood samples with low initial moisture content. This is explained by mould growth on the wetter samples, which termites don\"t tolerate in large amounts. The loss of wood mass due to termite attack could be reduced by using PLEOT. The mortality of termites was higher in test systems with protected wood samples than untreated samples. PLEOT could be used successfully against fungal attack. The treatment reduced on the one hand mould growth in a termite test and on the other hand reduced strongly the attack of brown rot fungi in a lab test.
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The aim of this study is to see if the raw material influences fixation and leachability of wood preservatives. Moving towards more eco-friendly and –concious society, the wood industries must adjust itself to new rules and regulations. Greener solutions in wood protection are being tested and introduced, older systems are being improved, but questions still arise concerning some elements currently used in wood preservation. Preservatives leaching into the nature is a problem, especially agents that consist copper. Studies have been conducted on the raw material`s influence on impregnability and variations in sapwood penetration have been found. This gives reason to believe that the leaching of wood preservatives is also influenced by the raw material. This study tries to set the variation of leachability of Wolmanit CX-8 and Tanalith into a system, evaluating the origin of a tree and the origin of a sample. The study uses Scots pine (Pinus sylvestris) as a raw material. Material was harvested from different stands in Norway and Denmark. Pine`s sapwood was cut into samples in size of 20x20x50mm. The samples were treated with the wood protection agents Wolmanit CX-8 and Tanalith. The variation in leachability within trees, between trees and between different stands was studied. Within this material, it is possible to trace the individual sample to its original position in the stem. Samples were climatized, impregnated with preservatives and leached according to standard EN84. Copper and boron content in water samples was determined by an ICP (Inductively Coupled Plasma) technique. Comparing leaching results with different variables, correlation was found with latitude and vertical position of the sample, indicating that southern stands leach out more preservative. The lowest part of the tree does not fixate preservatives.
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A combined wood impregnation process including impregnation with a chromium-free wood preservative and oil treatment was evaluated with regard to leaching of copper during the oil process. Two different experimental setups make up the balance of copper content in oil, wood samples and condensate water, also taking different fixation times and process durations into account. Copper is sufficiently fixed after 24 hours, and leaching of copper into the oil is low. Increasing the oil process time does not lead to increased leaching. The hot oil treatment of impregnated wood under vacuum atmosphere is a fast drying method without major negative consequences for the impregnated copper.
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Timber constructions are often built in combination with other materials such as concrete. These materials can influence the timber construction. Moist concrete can e.g. lead to development of molds which creates an unhealthy living area for people. Furthermore, moisture in wood buildings can negatively affect the wood material, which can lead to negative biological activity in timber and possible reduction of strength properties of timber constructions. The present paper introduces a new innovative method of timber protection and describes the influence of moisture on wood and concrete. The new environmental friendly system for protection of timber has been tested on wood destroying fungi and termites. It can be shown that wood protection by means of electro osmotic pulsing technology can preserve wood in laboratory trials. The wood moisture content is reduced when the protection system is installed. Trials on protected wood against subterranean termites showed lower wood moisture content after test of protected samples compared to untreated samples. However, termite activity could not be reduced to a larger extend as the termite living surroundings were not included. It could be shown that humidity in pores of concrete in cellar walls is reduced using electro osmotic pulsing. The drying of concrete when combined with timber constructions can additionally help to reduce timber degradation as all protection measures that lead to a drier building are positive for fungi and subterranean termite control.
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Coated wooden claddings in building facades are widely used in the Scandinavian countries, and are often preferred to other materials. Wood is facing increasing competition from other materials that are less labor intensive at the construction site and materials with less demand for maintenance thru service life, and makes further development of wooden claddings essential. Growth of discoloring moulds on exposed coated wooden claddings is mainly of aesthetic concern, and is especially disfiguring for light-colored surfaces. Growth of surface fungi often initiates repeated cleaning and shorter maintenance intervals, which in turn increase the total cost of ownership for wooden claddings. Cost and effort of ownership are often important factors considered when choosing a product, and the traditionally good market situation for wooden claddings is therefore threatened. The development of real-time PCR (polymerase chain reaction) and taxon-specific primers has provided new possibilities for specific detection and quantification of fungi in their natural substrates. In qPCR (quantitative real-time PCR), the accumulation of the PCR product is detected for each amplification cycle. An efficient and reproducible sampling and extraction of DNA is required for a high-throughput qPCR based quantification of discoloring fungi. The authors have now adjusted DNA isolation protocols and optimized real-time PCR assays for species specific detection of fungi frequently found on painted surfaces (Aureobasidium pullulans, Alternaria alternata, Cladosporium cladosporides, Ulocladium atrum).
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Wood as a hygroscopic material gains or loses moisture with changes in climate of the surrounding air. The moisture content influences strength properties, hardness, durability and machinability. Therefore the hygroscopicity is a very important property, last but not least for economic factors. Below fibre saturation, a change in moisture content causes shrinkage or swelling and anisotropic behaviour can be seen in the different growth directions. For a better understanding of the sorption behaviour of Scots pine (Pinus sylvestris L.) the variation between different adsorption and desorption curves has been investigated. Trees from 25 different sites in Northern Europe were collected and 3651 samples (1510 heartwood- and 2141 sapwood-samples) measuring 5 (T) x 10 (R) x 30 (L) mm were obtained. The sorption isotherms for all specimens were measured at 25 °C at relative humidities of 15, 35, 55, 75 and 95 % for both desorption and adsorption. The aim of this study is to investigate the influence of raw material variability on the sorption behaviour of Scots pine. Due to the different growing conditions, densities and wooden material (heart or sapwood) variations within the sample groups have been found. Correlations between moisture and density respectively latitude were investigated.
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Several studies have been conducted on impregnability of the raw material and large variations have been found. The leaching of wood preservatives into nature is a problem, especially agents that consist copper. Leachability of i. e. copper has been studied by several authors. This study tries to set the variation of leachability of Wolmanit CX-8 and Tanalith in system, evaluating the origin of a tree and the origin of a sample. Samples of Scots pine sapwood (Pinus Sylvestris) (20×20×50 mm) were treated with the wood protection agents Wolmanit CX-8 and Tanalith. The variation in leachability within trees, between trees and between different stands of Scots pine (in Norway and Denmark) was studied. The samples were climatized, impregnated with preservatives and leached according to standard EN84. The study indicates differences between the products. Stand location and samples position in a tree play a role in preservative leaching from wood, favouring southern located trees to be more prone to loosing preservative. Also the lowest part of the tree does not fixate preservatives as well as the upper parts.
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A new protection system has been tested which protects wood without treating it - by installing a low pulsing electric field. This electro-osmotic pulsing technology on wood, called PLEOT, has been tested in lab trials. Wood has a low specific conductivity and is considered as a dielectric material. Water plays therefore an important role. With increasing wood moisture content, a favorable environment for fungi development is created. At the same time, increasing wood moisture content increases the conductivity in wood and PLEOT can protect the material. Wood can be considered as naturally protected against fungal attack at a wood moisture content <20 %. It could be shown in lab tests, that a protection by means of PLEOT can be achieved at higher wood moisture content....
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Trebaserte produkter bidrar til å redusere klimautslipp, både ved å lagre karbon, ved å erstatte produkter som krever mye fossil energi ved produksjon og ved at det benyttes som fornybar energi. Forskningen ved Seksjon treteknologi omfatter en rekke disipliner som mykologi, treteknologi, kjemi og molekylærbiologi. Den nyeste forskningen på seksjonen bruker pulserende likestrøms elektro-osmoseteknologi (PLEOT) til å beskytte treprodukter mot soppangrep.
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Levetiden til trebygninger og trekonstruksjoner avhenger hovedsakelig av type konstruksjon, klima, type bruk, naturlig holdbarhet av trevirket, mulige bevaringsbehandlinger og tilstedeværelse av organismer som angriper trevirke.
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Coated wooden claddings in building facades are widely used in the Scandinavian countries, and are often preferred to other materials. Wood experience an increasing competition from other materials that are less labor intensive at the construction site and materials with less demand for maintenance thru service life, and makes further development of wooden claddings essential. Growth of discoloring moulds on exposed coated wooden claddings is mainly of aesthetic concern, and is especially disfiguring for light-colored surfaces. Growth of surface fungi often initiates repeated cleaning and shorter maintenance intervals, which in turn increase the total cost of ownership for wooden claddings. Cost and effort of ownership is often an important factor considered when choosing a product, and the traditionally good market situation for wooden claddings is therefore threatened. The development of real-time PCR (polymerase chain reaction) and taxon-specific primers has provided new possibilities for specific detection and quantification of fungi in their natural substrates. In qPCR (quantitative real-time PCR), the accumulation of the PCR product is detected for each amplification cycle. An efficient and reproducible sampling and extraction of DNA is required for a high-throughput qPCR based quantification of discoloring fungi. The authors have now adjusted DNA isolation protocols and optimized real-time PCR assays for species specific detection of fungi frequently found on painted surfaces (Aureobasidium pullulans, Alternaria alternata, Cladosporium cladosporides, Ulocladium atrum).
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Til laftevirke benyttes som regel grove tverrsnittsdimensjoner med innesluttet marg. Når virket tørker oppstår det sprekker. Sprekkene vil normalt ta korteste vei fra overflaten og inn mot margen. På laftevirke, som er kantet på to sider, dannes det gjerne en dyp sprekk i hver sideflate.
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Scots pine (Pinus sylvestris) and especially its heartwood is one of the most common construction materials for general outer use e.g. windows or facades in northern Europe. It is considered being use class 3 and is according to EN 350-2 \"not treatable\". Reports from industry and researchers indicate that the heartwood treatability is not uniform. It is still unclear what causes these differences. To increase its durability by means of impregnation would be a contribution to extend the use of both a natural and native material. The understanding of a potential pattern analog to latitudinal/longitudinal origin or other forest or wood properties could help to improve the impregnation by better material selection. Scots pine samples from 25 different sites in 6 countries in northern Europe have been collected throughout autumn and winter 2009/2010. A circle of varying size containing approximately 30 trees was set up in a representative site of each stand. All diameters were measured and arranged in three classes. Three trees of each class were chosen randomly. Only the middle and upper diameter classes were used for studying heartwood permeability. The small diameter class had insufficient heartwood width to be processed. Samples of 20 x 20 x 50 mm were cut and conditioned in a climate chamber. The samples were impregnated with a water-soluble monomer furfuryl alcohol solution in a standard pressure/vacuum process. Results showed a generally low permeability but a few samples had an unexpected high ration of filling. Further on, the samples with the highest and lowest treatability will undergo anatomical and chemical tests to explain these properties.
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Scots pine (Pinus sylvestris) sapwood was investigated for variation in treatability using the wood modifying agent, furfuryl alcohol (FA) in water. The variation in treatability within trees, between trees and between different stands of Scots pine was studied. Investigated variables that reduced the residual variance significantly were: site location, latitude of site, height of trees, annual ring width, vertical and horizontal position in the tree and method of drying. Linear mixed model statistics were used and tree number was handled as a random variable. The best model reduced the treatability residual variance by 67%. Location was the single factor affecting treatability most. Differences in latitude between locations may be the reason for that. Latitude correlated negatively with the treatability. Within the trees, the treatability of sapwood increased with distance from ground and with distance from heartwood border. A small, but significantly better treatability was found for kiln dried wood (60A degrees C) compared to air dried wood (20A degrees C).
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Scots pine (Pinus sylvestris) sapwood is per definition (EN-350-2) easy to treat. Combination with its good availability on the European markets, it is a construction and building material in demand. However, partially large differences in penetration are reported from industry and research. To keep a reliable product quality, impregnation processes aligned to the material most difficult to treat. Hence, it is crucial to know about the factors inhibiting the fluid flow into the material. Scots pine samples from a wide geographic distribution, 25 different sites in 6 different countries, have been collected and impregnated with an aqueous monomer furfuryl alcohol solution. From each of the respective sites logs of 1.3 meter in length were collected from nine trees belonging to three different breast height diameter classes. Three trees from each dominance class were chosen randomly. The log was drawn from the felled stem in a height of 1.2 meters with exact marked north/south exposition. Sapwood slabs orientated in the heaven directions, underwent a drying procedure at 40°C for 48 h and small clear samples of 20 x 20 x 50 mm were prepared. A large variation of the ratio of filling was found for the material tested. Diameter as well as sample origin seem to influence the materials permeability.
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Wood protection is mainly based on chemical protection of wood. The disposal of wood preservative treated material causes restrictions in its later use or recirculation into the eco-cycle. A new protective system, electro-osmotic pulsing technology on wood, called PLEOT, is tested in a fungi test and in soil contact. Mass loss and moisture content of Scots pine sapwood samples was calculated after testing and an element analysis was performed on the sample powder. The results show that PLEOT- protected samples have nearly no mass loss after 4, 8 and 12 weeks of exposure to Coniophora puteana in laboratory trials. The samples protected with PLEOT showed lower moisture content but trace elements of metals in the samples after basidiomycete test compared to untreated samples. It is concluded, that neither the resulted wood moisture content nor the transferred metal ions in the PLEOT samples contribute to large amounts to the wood protection effect. Furthermore, the PLEOT system might give a protection for wood in soil contact. Further research on the mode of action as well as further tests including field tests are under planning.
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One of the biggest drawbacks of using European native wood species as a construction material is its tendency to degrade by fungal attack. This has lead to the development of different systems for wood preservation. Many of these systems suffer the disadvantage that they contain biocides, which can leach from the wood into the environment and damage organisms. In this project ten silanes, 3-(2-Aminoethylamino)propyltrimethoxysilane, 3-[2-(2- aminoethylamino)ethylamino]propyltrimethoxysilane, 3-Aminopropyltrimethoxysilane, Diethoxydimethylsilane, Dodecyltriethoxysilane, Hexadecyltrimethoxysilane, NTrimethoxysilylpropyl- N,N,N-trimethylammoniumchloride, Octyltriethoxysilane, Octyltrimethoxysilane and Phenyltrimethoxysilane, have been investigated for their ability to increase the hydrophobicity of wood and decrease shrinking and swelling, and thus increase its ability to withstand attack by fungi. In the initial phase of the project two solvents, ethanol and water were investigated to find out which of these that gave the best result for surface modification with silanes. The results showed that water as solvent gave a surface with higher hydrofobicity than when ethanol was used as solvent....
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The durability of wood in exterior use is limited by to climatic factors and wood deteriorating organisms. The natural durability of the Nordic wood species is generally regarded as low, and for e.g. decking and use in soil contact wood protection is needed. Within the last years, new non-biocidal treatments, like wood modification systems, have been developed to improve the biological resistance of wood. For information about the decay resistance of untreated and modified wood, natural outside exposure is necessary. European standard EN 252 is the main field test method for use class 4. In use class 3 the need of new or improved test setups has been put forward. Traditionally evaluation of field trials has mainly been based on visual evaluation and pick-test. However, to get in depth knowledge about: 1) different field trial methods and 2) fungal colonization of new wood protection systems, additional assessment methods can be used. Hence, comparative studies are needed.....
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New environmental benign wood protection agents often come from natural resources, and are sometimes a waste product. Chitosan, a derivative from chitin which is among other sources a by-product from the shellfish industry, is tested as well as known wood protection agents and their synergetic effect with chitosan. The objective of the research presented in this paper, is to describe the leaching properties of the following compounds: Chitosan, chitosan/copper, chitosan/boron and chitosan/ScanImp (a commercial wood preservative). A leaching procedure was performed on treated Scots pine sapwood samples. The four solutions have also been tested with and without post treatment. A new effective fire preservative has been included in the test. Common wood preservatives have been tested as references. The combination with chitosan did improve the fixation of the wood protection agent ScanImp. Furthermore, the post treatment of the chitosan treated samples did significantly reduce the leaching of glucosamine and to some extend also the leaching of boron.
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Til laftevirke benyttes som regel grove tverrsnittsdimensjoner med innesluttet marg. Sprekker oppstår når virket tørker. Sprekkene vil normalt ta korteste vei fra overflaten og inn mot margen, noe som medfører at det på laftevirke som er kantet på to sider gjerne dannes en dyp sprekk i hver sideflate. En slik lokalisering av sprekker kan bidra til å redusere kvaliteten på laftede konstruksjoner på flere måter. De kan redusere varigheten til virke som eksponeres for uteklima fordi det har lett for å samle seg fuktighet i sprekkene, noe som fører til at miljøet for råtesopper blir begunstiget. I tillegg bidrar sprekkene til å øke overflatearealet, og på den måten blir det et større område som eksponeres mot råtesopper. Sprekkene vil dessuten føre til økt varmetap i veggene og dermed føre til økt energiforbruk i byggets bruksfase. I tillegg kan sprekkdannelsene virke estetisk skjemmende. Denne undersøkelsen er basert på 39 lafteplanker produsert av furutømmer med lengde 5 m og en diameter egnet produksjon av lafteplank med tykkelse på 150 mm. Tømmeret ble på forhånd delt inn i 4 grupper for videre behandling: A. Margskjæring med motorsag (inn til margen) B. Sirkelsagskjæring (9 cm dypt) C. Sirkelsagskjæring (4,5 cm dypt) D. Kontroll (ubehandlet)
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Wood is a traditional building material but in general it underlies restrictions in outdoor applications due to its respective durability against microbiological decay. To face this problem, different impregnation systems are applied to enhance the materials\" servicelife. Scots pine (Pinus sylvestris) is the most widely distributed pine in Eurasia and hence easily available. Despite of the previously defined good treatability of Scots pine sapwood, large differences in treatment performance are reported from industry. As process parameters are always adjusted to the material most difficult to treat, permeability variations in wood material are an economical problem. Therefore, it is important to understand the material in order to make a more reasonable material selection possible.....
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New restrictions draw governments, industry and research towards new and environmental benign wood protective agents. These agents often come from a natural source, and are also a waste product. One of these is chitosan. Chitosan is a derivative from chitin, mainly found in the exoskeleton of crustacean. Some research has been conducted on chitosan and wood. Chitosan has earlier proven good antifungal effectiveness, but to achieve a good protection, a 5 % concentration is needed, which makes the end product quite expensive. In recent research, a way to make chitosan treated wood hydrophobic has been invented. The objective of the research presented in this paper, is to describe the effectiveness of the following compounds: Chitosan, chitosan/copper, chitosan/boron and chitosan/Scanimp (a commercial wood preservative). Results show that chitosan works well alone, but has a fixation problem. Chitosan and boron give good fixation, and reduced amounts of chitosan and together give good protection against wood destroying fungi. The fire protection agents are promising, but needs higher concentration and/or better fixation to give a sufficient protection against wood destroying fungi
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Forskere ved Skog og landskap og Universitetet for miljø- og biovitenskap (UMB) har, sammen med industrien, oppdaget at det er variasjoner i opptak av impregneringsvæske ved trykkimpregnering. Dette skyldes til dels forskjeller mellom furubestand. Den største forskjellen skyldes breddegrad. Det vil si at furu fra sørlige bredde grader lettere lar seg impregnere enn furu fra nordlige breddegrader.
Forfattere
Erik LarnøySammendrag
To evaluate the decay resistance of wood, treated or untreated, for hazard classes 3, 4 and 5, the mass loss due to fungal exposure needs to be calculated. The standards for calculating mass loss in wooden test samples (i.e EN 113 and ENV 807) require that the samples used in the test are pre-dried to 0 % moisture content, m0, for determination of the initial dry mass. The standards describe that the samples should be dried at 103±2°C for 18 hours. When drying wood samples to 103 °C the samples are altered. Literature describes that extractives are influenced at temperatures as low as 60 °C, and redistribution and/or evaporation of these, will change the characteristics of the wood samples...
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- Hvis man tar utgangspunkt i den energien som tømmeret representerer, går mindre enn 3 % av denne med til å fremskaffe dette tømmeret til industrien. Om lag halvparten av energiforbruket fra skogetablering til industritomt er knyttet til tømmertransport. - I livssyklusfasene til boliger og kontorbygg er det bruksfasen som utgjør det største energiforbruket, ca. 85-93%. - Drivhusgassbalanse og energi som går til gjenvinning, vil i stor grad avhenge av hvordan tre behandles etter riving og eventuell substitusjon av fossilt brensel. For trekonstruksjoner er den energien som frigjøres ved forbrenning av rivingsvirke, minst like stor som den energien som kreves til fremstilling av trekonstruksjonene. - I 95 % av de gjennomgåtte studiene i denne undersøkelsen der tre ble sammenlignet med alternative materialer, har man kommet til at tre var like bra (35 %) eller bedre (60 %). - Gode levetidsdata for tre og trekomponenter er helt avgjørende for gode LCA analyser. Økt levetid på bygningsdeler i tre vil kunne bidra til økt karbonbinding. Det er derfor av stor betydning å finne nye trebeskyttelsessystemer som bidrar til økt levetid. - Nyere undersøkelser peker i retning av at den største samlede reduksjonen i CO2-utslipp til atmosfæren oppnås ved å drive et intensivt skogbruk. Dette er basert på forutsetninger om at biomassen fra skogen benyttes til å substituere mer energikrevende produkter, samt til substitusjon av fossilt brensel. I praksis vil et intensivt skogbruk kunne komme i konflikt med en del av kravene som er satt til et bærekraftig skogbruk.
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The variations on the ratio of filling (RoF) were investigated on Norwegian grown Scots pine (Pinus sylvestris). The samples were taken from 10 different stands in south-east Norway, and treated with furfuryl alcohol and a copper-containing wood preservative. Both within tree variations, between tree variations and variations between stands were investigated for significant differences. Factors like horizontal and vertical positioning of the stem, annual ring width, density, tree height, tree age and latitude were tested. Samples of 20 x 20 x 60 mm were impregnated with a mild treatment scheme to avoid full penetration, which made it possible to distinguish the RoF. A significant variation was found between copper impregnated a furfuryl treated samples, favouring the copper impregnated samples. Within tree variations show a positive significance of the first log compared to the other logs, and a higher RoF in younger sapwood. The latitude of the stand gave a strong correlation, favouring southern stands.
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The treatability of Scots pine (Pinus sylvestris) sapwood is ranked in the European standard EN 350-2 as class 1 (easy to treat), although huge differences in sapwood penetration exist. To obtain full sapwood penetration, process parameters have to be adjusted to the material most difficult to treat. It is therefore of importance to understand the factors that are responsible for penetration differences. Scots pine sapwood was investigated for anatomical differences influencing the ratio of filling (RoF) when treated with the wood modifying agent furfuryl alcohol. The database for the study was samples from two test series including Scots pine from Norway and Denmark. Within these experimental series each sample can be reassigned to its original position in the stem. The RoF for each sample was evaluated, and the variation in treatability within trees, between trees and between different stands was studied...
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The effectiveness against soft rotting micro fungi and other soil inhabiting micro-organisms was tested according to ENV 807 using different treated Scots pine sapwood and beech wood samples. The treatments differed in basic material, solvent, depolymerization agent, viscosity and post treatment. The chitosan treated Scots pine samples showed improved performance against soft rot, whereas a large amount of untreated pines sapwood samples failed during the test. The different chitosan treatments showed only slight differences in performance during the test.Further results of ongoing field tests should give more information about the life performance of the treated samples.
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The aim of this study was to use Energy-Dispersive X-ray Spectroscopy (EDS) to localize chitosan in the cell wall of chitosan impregnated Scots pine. It is of both general and specific interest to investigate the concentration of chitosan in the wood matrix to gain further knowledge and understanding of chitosan as a wood protective system.After deacetylation, chitosan was re-acetylated with chloroacetic anhydride to achieve a covalent bonding of chloride to the chitosan polymer. Chloride labeled chitosan was measured by EDS using a Scanning Electron Microscope (SEM) and described in apparent concentration of chloride. Analysis for free chloride anions was tested by dialysis and ion chromatography.There was a significant correlation between the molecular weight of chitosan and the apparent concentration of covalent bonded chloride to the chitosan polymer. High molecular weight chitosan showed a better interaction with the cell wall structure than low molecular chitosan.
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Furfurylated wood has shown to have promising properties for a wood modification agent during the last years. In this paper, an alternative curing method for furfuryl alcohol modified pine sapwood by means of microwave radiation was investigated. Different process parameters of microwave treatment such as output power, exposure time to microwave radiation, initial wood moisture content and evaporation during treatment, were tested. The weight percent gain of pine wood samples due to polymerised furfuryl alcohol was investigated by means of thermo gravimetric analysis. Leaching of furfuryl treated and differently cured samples gave information about the degree of fixation. No distinct influence of initial moisture content could be stated. A slight tendency of improving the degree of fixation by increasing the consumption energy of wood samples due to microwave energy was found. Changing the evaporation ability of samples during microwave treatment by using plastic foil had no distinct influence. Fixation of furfuryl alcohol could be improved by microwave treatment, and a degree of fixation above 90 % was calculated. However, the fixation was lower than in oven cured samples.
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Furfurylated wood is an environmentally friendly, chemically treated, wood product with improved characteristics. Quality control of furfurylated wood is still performed manually by subtracting the initial weight of a treated sample from its final weight, then dividing the result by the initial weight. Expressed as a percentage, this results in a value that represents the weight percent gain (WPG) of the treated sample and thus the degree of modification. The major disadvantage of this quality control method is that the production parameters are needed to determine WPG, since the initial weight cannot be deduced from a treated wood sample. In this paper the use of ThermoGravimetric Analysis (TGA) is presented as a potential quality control method for furfurylated Scots pine (Pinus sylvestris L.). The technique is independent of production parameters and, therefore, enables third parties to determine the WPG of any furfurylated wood product. Three validation trials have been performed with the same validation samples, but varying TGA settings and with different Partial Least Square regression models (PLS-models). Although the method needs further improvement, it has shown good accuracy and precision. Therefore, it is con
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Furfurylated wood (wood modified by furfuryl alcohol) has over the last years gained marked shares from both tropical wood and conventional preservative treated wood and this has, in turn, generated several research projects concerning process development. The impregnation of spruce is well known from literature to be a difficult task. Furthermore, the sapwood of Scandinavian grown Scots pine is also known to be difficult to fully impregnate from time to time. The primary objective of the study was to evaluate whether the Oscillating Pressure Method (OPM) could be used to impregnate green and dry Norway spruce wood (Picea abies) with a Furfuryl alcohol (FA) - mixture. The secondary objective of the study was to evaluate if OPM could improve the penetration of FA in Scots pine (Pinus sylvestris) as compared to conventional full cell (Bethell) treatment. Impregnation tests were carried out on boards and planks as well as 300 mm and 500 mm clear wood samples. Samples were removed for MC measurement and the initial weight of the test samples was determined. Four different impregnation schemes were tested. The results indicate that Norway spruce can be impregnated by the OPM method to produce a protective shell of treated wood around a core of untreated wood. The penetration in Spruce showed great variation between different boards and between different parts of the individual boards. This is in part expected, but can also be caused by uncontrolled pre drying of the test material which was stacked uncovered after sawing. For Scots pine, the OPM improved the penetration of both sapwood and, to some extent, the outer heartwood.
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The objective was to evaluate whether Lowry-impregnation of Scots pine with FA100-mix, instead of the FA40-mix, would lead to similar or slightly higher WPGs and to investigate any potential changes in penetration pattern. The results indicate that the penetration was better, also penetrating the outer zone of the heartwood. Furthermore, it was possible to reduce the WPG-levels for pine down to 50-70% (corresponding to PFA retentions of 260- 315 kg/m³) from 120% (approx. 550 kg/m³) with full-cell impregnation using FA100-mix. Using the Lowry process with FA100-mix would probably be a possible treating schedule for products aimed for use in ground contact. The reduced content of hygroscopic salts in the furfurylated wood product would also further reduce hygroscopisity compared with FA-40 mix. However, more trials are needed in order to optimize penetration while still keeping the final WPG low.
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The aim of this study was to compare two methods for non-destructive strength testing of wood by the use of dynamic modulus of elasticity (MOEdyn). The two methods are based on resonant vibration excitation and ultrasonic pulse excitation. Sound Pinus sylvestris L. sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated at two moisture levels. There was a significant correlation between the measurements given by the two MOEdyn test devices. An analysis of variance showed significant differences between the different treatments and between different moisture levels. Potential use of the non-destructive MOEdyn methods in durability testing is discussed.
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When using chitosan as an antifungal agent in wood it is important to understand which factors contribute to a higher fixation ratio to optimize the utilization of chitosan, the active component. Small pine samples were impregnated with chitosan solutions varying in molecular weight, concentration, pH, polymerization agent, acid and degree of deacetylation. Different post-treatments such as time, temperature, moisture content and the effect of present air were applied to the samples to evaluate the effect on the relative retention. After impregnation, the samples, with a volume of 1.5 cm3, were leached in separate test-tubes according to EN-84. The samples were prepared in a paired design where both samples were impregnated, but only one was leached. Both leached and unleached samples were analysed for their chitosan content, and the relative ratio was used as a measure for the relative retention of chitosan during leaching. The results from these trials show that pH in the range of 5.1-5.9 is favourable. The molecular weight should be as high as possible yet able to penetrate the wood structure, and the use of acetic acid gives far better fixation than the use of hydrochloric acid.
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There is a high correlation between methods for dynamic modulus of elasticity (MOEdyn) and static modulus of elasticity (MOEstat). MOEdyn methods have been found sensitive to detect early stages of decay and may be seen as an option for non-destructive wood durability testing.As the MOEstat measurements do not change after reaching the fibre saturation point, the uncorrected MOEdyn data from ultrasonic pulse excitation method provides increasin values after fibre saturation. This is due to the effect of free water in the cell lumen on ultrasonic waves. The aim of this study was to make a moisture calibration for the MOEdyn ultrasonic pulse excitation method using Scots pine (Pinus sylvestris L.) sapwood samples.MOE was measured at five different moisture levels. Three different MOE test methods were used: MOEdyn using ultrasound and vibration excitation and the traditional MOEstat. Sound Scots pine sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated, using untreated sapwood samples as control.In this study a correction value (\"k\") was calculated based on data from different moisture levels for water saturated samples using four different wood treatments and control. By measuring MOEdyn ultrasonic at wood moisture contents just below fibre saturation point, a minor effect of incipient water accumulation in the wood matrix was detected.Wood treatments influence the \"k\" value, and a \"k\" value needs to be calculated for all wood treatments when measuring MOEdyn ultrasound above fibre saturation. All the three MOE test methods in this study are applicable for all wood moisture levels as long as a \"k\" value is calculated for MOEdyn ultrasound above fibre saturation.
Forfattere
Erik LarnøySammendrag
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The uptake of chitosan based impregnation solutions were tested on Scots pine (Pinus sylvestris L), Beech (Fagus sylvatica L.), Downy birch (Betula pubescens Ehrh.) and Norway spruce (Picea abies L. Karst.) in longitudinal, radial and tangential directions separately. The four chitosans tested had a fraction of acetylated residues (FA) of 0.198 and average molecular weights ranging from 18 to 129kDalton. The kinetic viscosity of the 2.4% (weight/volume) solutions at pH 5.0 was in the range of 2.95 to 28.8mm2s-1. The general trend showed that there was an increase in uptake of chitosan based impregnation solutions with decreasing viscosity, and the chitosan solution with the lowest viscosity had almost comparable uptake with water for Pine and Beech in the longitudinal direction. In general, the lower the ability for uptake of impregnation solution, the more the viscosity influences the uptake.
