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Wood furfurylation process and properties of furfurylated wood
2004 - IRG/WP 04-40289
The first processes for “furfurylation” of wood (wood modification with furfuryl alcohol) were developed several decades ago. Furfuryl alcohol is a renewable chemical since it is derived from furfural, which is produced from hydrolysed biomass waste. Over the last decade modernised processes for furfurylation of wood have been developed. These new processes are based on new catalytic systems and process additives. Two main processes for production of furfurylated wood have been developed for WPT (Wood Polymer Technology ASA) by the authors – Kebony 100 for high modification levels of hardwoods and VisorWood for lower modification levels of pine. Commercial production according to the Kebony process has been running since August 2000, mainly for flooring. A small Kebony production plant is now in operation in Lithuania. A larger Kebony/VisorWood production plant started up in September 2003 in Porsgrunn, Norway. Several new plants operating according to the VisorWood process, each with an annual capacity of 10 000 m³ or more, are under construction. The properties of furfurylated wood depend on the retention of grafted/polymerised furfuryl alcohol (PFA) in the wood. At high modification levels (high retention of PFA) the enhancement of a wide variety of properties are achieved: an exceptional hardness increase, exceptional resistance to microbial decay and insect attack, high resistance to chemical degradation, increase in MOR & MOE, and high dimensional stability. At lower modification levels many property enhancements also occur, however to slightly lower extent. Notable are resistance to microbial decay and insect attack, increase in MOR & MOE, and relatively high dimensional stability.
M Westin, S Lande, M Schneider

Durability of pine modified by 9 different methods
2004 - IRG/WP 04-40288
The decay resistance was studied for pine modified by nine methods of wood modification: 1) Acetylation, 2) Treatment with methylated melamine resin (MMF), 3) Acetylation followed by post-treatment with MMF-resin, 4) Thermal modification, 5) Furfurylation, 6) Maleoylation (using water solution of MG or ethanol solution of maleic anhydride), 7) Succinylation, 8) NMA-modification and 9) modification with reactive linseed oil derivative (UZA), Wood blocks of Scots pine (Pinus sylvestris L.) sapwood were modified in pilot plants. Methods 1-5 were performed by the authors at Chalmers University of Technology or at BFH in Hamburg. Methods 5-9 were part of a European research project (the Chemowood project, FAIR-CT97-3187) and therefore each of these modifications was performed by the project participant responsible for the method. For laboratory testing in TMCs (modified European standard ENV 807) and pure basidiomycete culture bioassays, smaller test specimens were cut from the modified wood blocks. Most of the modification methods were applied on test specimens for marine field testing (EN 275) and some methods to produce mini-stakes for field tests in five Swedish fields. Some modification methods result in modified wood with poor durability, whereas other methods (acetylation, furfurylation and MMF-treatment) seem to provide excellent resistance to microbial decay.
M Westin, A O Rapp, T Nilsson

Novel wood modification processes for window and cladding products
2004 - IRG/WP 04-40285
Because of the low natural durability and low dimensional stability of European wood species, the usage of wood for window frames has decreased dramatically during the last decade. In a joint project of several German research institutes and the window industry, following wood modification systems were compared. heat treatment (3 different materials from 2 companies) acetylation (pine sapwood and beech wood acetylated with acetic anhydride) polymerisation (melamine resin treated pine sapwood, Interlace treatment, furfurylation) wax treatment (pine sapwood, which was impregnated with natural resin and waxes) Investigated was the moisture content, dimensional stability, capillary water uptake and the durability. The dimensional stability show a high increase for following materials: heat treated wood, acetylated pine, interlace treated wood and furfurylated wood. The melamine resin treated wood and the wax treated wood show no significant increase in the dimensional stability. The biological durability against different basidiomycetes was tested according to the EN 113. As test fungi, Coniophora puteana, Poria placenta and Coriolus versicolor were used. The results show a very high increase in the durability for most of the treated wood. The wax treated wood shows no significant increase in durability. A novel window frame consists of several functional layers. Different wood properties are demanded for the single layers to achieve optimal window properties. Every modified wood shows a special potential for the use in a functional layer.
A Krause, C Hof, H Militz

Improving the weather resistance of glue-laminated jarrah and karri
1994 - IRG/WP 94-40017
Surface modification and dimensional stabilisation significantly increased the dry and wet shear strength of karri and jarrah lap-shear specimens (laminates) bonded with resorcinol formaldehyde. The combination of surface modification (sanding/sodium hydroxide treatment), and furfurylation produced the highest dry and wet shear strengths. Acetylated laminates had the lowest dry bond strength, but the lowest loss of strength on wetting. In most cases karri laminates showed higher dry, but lower wet shear strength than jarrah. Untreated laminates rapidly delaminated during artificial accelerated weathering, but surface modification and dimensional stabilisation significantly increased the resistance of specimens to delamination. Only a small proportion (5-10%) of acetylated specimens delaminated during accelerated weathering and surface modified acetylated laminates showed no delamination during the weathering test. Laminates treated with a combination of surface modification and furfurylation showed less delamination than specimens treated by surface modification alone. Treatments that increase both glue bond strength and dimensional stability appear to offer an effective means of improving the weathering resistance of glue-laminated karri and jarrah.
J Balfas, P D Evans

Chemical reactions involved in furfurylation of solid wood - An investigation by ATR-IR spectroscopy
2006 - IRG/WP 06-40347
Wood modification with furfuryl alcohol (FA) has gained renewed interest during the last five to ten years because of advances in process technology and because of increased focus on the environmental hazards of traditional wood impregnation. The reaction mechanisms involved in the furfurylation process are not yet understood in detail. In the work presented here, the chemical reactions and their end products in the wood cell wall were studied using Attenuated Total Reflection InfraRed spectroscopy (ATR-IR) and knowledge from molecular modelling. Evidence of a polymeric structure of FA in the cell wall was found, but bonding between wood constituents and FA or a FA-polymer could not be verified. Because of many overlapping absorbance peaks in the IR region, wood and FA absorbance bands are difficult to assign without support from extensive molecular modelling. Further modelling is needed to fully understand the possible reactions between wood and FA.
T Mark Venås, L Garbrecht Thygesen, S Barsberg

Furfurylated wood - An alternative to Preservative-treated wood
2006 - IRG/WP 06-40349
Chemically modified wood is currently being marketed as a non-toxic alternative to traditional preservative treated wood (wood impregnated with biocides). Over the last decade the authors have developed modernised processes for wood modified by furfurylation. These new systems do not add metals or halogens to the product, which is important for an environmentally acceptable product. This presentation deals with the environmental aspects and durability of furfurylated wood. Results from several decay tests; emission analysis studies and eco-toxicity tests are presented. . The results show that furfurylated wood is highly decay resistant. There was no significant eco-toxicity of water leached from furfurylated wood and burning furfurylated wood does not release any more volatile organic compounds or poly-aromatic hydrocarbons than normal levels for wood combustion. Durability enhancement by furfurylating wood has not proven to be harmful to the environment. Test results have shown it to have performance similar to traditionally preserved wood. Furfurylated wood has some improved mechanical and physical properties such as increased modulus of elasticity (MOE) and increased anti shrink efficiency (ASE).
S Lande, M H Schneider, M Westin, J Phillips

Wood furfurylation process development. Part 1: Oscillating Pressure Method
2007 - IRG/WP 07-40376
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.
E Larnøy, M Westin, B Källander, S Lande

Wood furfurylation process development. Part 2: Lowry impregnation trials
2007 - IRG/WP 07-40377
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.
M Westin, E Larnøy, S Lande

A step towards a better understanding of fungal colonization of modified wood - QRT-PCR studies
2008 - IRG/WP 08-10653
The area of wood protection is in a period of change. New wood protection systems have been developed while their mode of action remains insufficiently understood. The development of molecular methods provides potential tools to investigate the interaction between modified wood and decay fungi. One small step to tackle some of the unsolved questions about the mode of action of modified wood is taken in this study. A specific and quantitative real-time PCR (QRT-PCR) assay was now established for identifying and quantifying early stages of fungal colonisation in modified wood and for profiling growth dynamics of the white-rot fungus Trametes versicolor through different stages of decay. QRT-PCR of colonisation of three different wood modification systems (acetylation, furfurylation, thermal modification), two reference treatments (Cu-HDO, CCA) and Scots pine sapwood as control was performed. Incubation time was 2, 4, 6, 8 and 10 weeks. While the fungal colonisation in untreated control samples showed a continuous increase during the experimental period, the amount of fungal DNA in modified wood had an initial peek after two weeks, followed by a gradual decline. The furfurylated samples had lower fungal colonisation than all the other treatments except for Cu-HDO. In the reference samples of copper nearly no fungal colonisation was found at all during the study period of 10 weeks. In the CCA samples there was an initial colonization peek at 2 weeks, but for the remaining part of the experimental period the colonization level remained very low.
G Alfredsen, A Pilgård, A Hietala

Feasibility study on three furfurylated non-durable tropical wood species evaluated for resistance to brown, white and soft rot fungi
2008 - IRG/WP 08-40395
Furfurylation can protect non-durable wood species against biological degradation, but the method used today cannot fully protect the heartwood of Scots pine due to insufficient penetration. In order to test alternative wood substrates for furfurylation, three Malaysian grown wood species (Kelempayan, Rubberwood and Sena) were furfurylated and subjected to soil block decay testing. Their performance was compared to furfurylated Scots pine and furfurylated Beech modified using the same process. In addition, treatment characteristics were evaluated. One of the species tested, Kelempayan, seems to be a promising substrate for furfurylation. Kelempayan is easy to impregnate in both sap- and heartwood, and a 50% higher weight gain was reached using equivalent amounts of impregnation solution compared to Scots pine. Sena, Rubberwood and Beech returned weight gains 40-60% lower than Scots pine. Decay protection was largely comparable at equivalent weight percent gains for all wood species tested, although differences appeared. Generally, a weight gain of approximately 25% by furfurylation seems to offer good protection in the chosen soil block test.
T Mark Venås, A H H Wong

Postia placenta gene expression of oxidative and carbohydrate metabolism related genes during growth in furfurylated wood
2009 - IRG/WP 09-10701
A range of studies the last decade have shown that modified wood can provide excellent protection against a range of wood deteriorating organisms, including decay fungi. However, we still lack information about why the modified wood is protected from microbial attack. Several hypotheses have been put forward e.g. inhibition of action of specific enzymes, but they still need testing. An understanding of the mechanisms utilized by decay fungi when exposed to modified wood is important for further optimisation of new modified wood products. In this study gene expression of the brown rot fungus Postia placenta has been monitored after 2, 4 and 8 weeks of colonization in furfurylated Scots pine and control samples. Preliminary results are given. The main finding was that genes related to oxidative metabolic activity was higher in furfurylated wood compared to untreated Scots pine, and that carbohydrate metabolism related expression was lower in furfurylated wood compared to untreated control.
G Alfredsen, C G Fossdal

Termite resistance of some modified wood species
2009 - IRG/WP 09-40449
During the last few decades, researchers worldwide have investigated and developed new treatment techniques to improve intrinsic wood properties. Some of these techniques were introduced to the market recently and are gaining in importance.. Various wood properties of these new materials have been studied intensively. These include physical-mechanical properties (dimensional stability, moisture related properties) and the resistance against wood degrading fungi. However, only limited knowledge on the performance of these materials against subterranean termites is available. For this reason, two field trials were conducted in northern Queensland (Australia) against subterranean termites. Several wood modification systems were used (furfurylation, acetylation, DMDHEU, heat treatment, melamine). The results after 36 weeks of exposure, indicated a high feeding pressure in both trials, producing significant mass losses in the untreated feeder material (Pinus sylvestris). Most wood modification techniques failed against the subterranean termites Coptotermes acinaciformis and Mastotermes darwiniensis. Apart from the slash pine (Pinus elliottii) treated with copper, chrome and arsenic (CCA) salts standards, only dimethyloldihydroxy-ethyleneurea (DMDHEU)-treated slash pine performed well in the tests.
H Militz, B C Peters, C J Fitzgerald

Microscopy evaluation of microbial decay patterns in wood stakes after 6 years in soil contact
2010 - IRG/WP 10-10715
Most studies on wood modification have so far been concerned with service life predictions rather than investigating the decay protection mechanism. Very little is known about the mode of action of these new treatments and about the strategies used by wood degraders in order to utilize the wood material despite a treatment. Access to such knowledge would allow further modification and improvement of durability of these products. The aim of the present study was to investigate the variation in microbial degradation of wood samples exposed in soil, in an EN 252 field, test for six years. Light microscopy was used for assessing degree and type of decay. Wood stakes of furfurylated and copper organic treated P. sylvestris heartwood were compared to untreated stakes of P. sylvestris. Samples for analyses were taken from three different parts of each stakes; below ground level; soil surface region, and above ground level. In general, the degradation and decay by microorganisms was greatest in the soil surface area. Brown rot, white rot, soft rot and tunnelling bacteria were found degrading the wood. Variations in decay were observed between furfurylated wood and copper organic treated wood. White rot decay were most common in furfurylated wood, where as brown rot were only present in copper organic treated wood. Soft rot was found active in a majority of the stakes. Furfurylated stakes treated to a medium treatment level were more resistant to soft rot decay than furfurylated stakes treated to a low treatment level.
A Pilgård, C G Björdal

Durability of Furfurylated Wood – Results from Laboratory and Field Tests in the Ecobinders project
2012 - IRG/WP 12-40602
Within the EU project Ecobinders, laboratory tests were performed with furfurylated wood produced in semi-industrial scale in the factory of Kebony ASA. Field trials in Horizontal double layer decks and in-ground of transmission poles were also started. Four wood species, Southern yellow pine (SYP), maple, beech and aspen were treated to two treatment levels by using two impregnating liquids with different furfuryl alcohol content. Full length Scots pine poles were only treated with the higher furfuryl alcohol concentration treating liquid. SYP and beech samples were tested according to EN113 and maple and aspen samples according to the corresponding American test, AWPA E10. All wood species except Scots pine, at two treatment levels were installed in a HDL deck and the poles in ground with a creosoted pole as reference. The laboratory tests with three test fungi showed very consistent results. The low FA-content treating liquid (FA40) resulted in durability class 2-3 and the higher FA-content treating liquid (FA70) resulted in Durability class 1. After these tests Kebony ASA decided to switch from FA40 treating liquid to FA70 treating liquid in all of their production and is still using this mix in the production. The field trials were started in 2006 and after 5 years all 6 furfurylated poles (WPG=40 in the sapwood zone) were sound, which is, however, also the case for the creosoted pole reference. In the HDL test all furfurylated test stakes are more or less sound, whereas the controls are moderately to severely decayed.
M Westin

The impact of catalyst on the properties of furfurylated beech wood
2016 - IRG/WP 16-40748
European beech (Fagus sylvatica L.) is a major tree species of European forest that is underexploited because of its low dimensional stability and durability. Similarly to what has been developed with radiata pine, furfurylation might be the answer to optimize the utilization of local beech wood. Beech wood furfurylation process was studied using five different catalysts: maleic anhydride, maleic acid, citric acid, itaconic acid and tartaric acid. Optimization of the furfurylation process was investigated for different catalyst and furfuryl alcohol (FA) contents, and different duration of polymerization. The following properties were studied: weight percent gain (WPG), leachability, anti-swelling efficiency (ASE), wettability, modulus of elasticity (MOE), modulus of rupture (MOR), Brinell hardness (BH), and decay durability. Tartaric acid, never investigated up to now, was retained as catalyst to optimize the furfurylation process conditions due to its efficacy compared to other catalysts. Wood modification with FA and tartaric acid as catalyst led samples with high WPG even after leaching, improved ASE and lower wettability with water. Increasing the polymerization duration increased the fixation of FA in treated wood. Most of all, treatment gave a significant improvement in mechanical properties and resistance to wood decaying fungi.
P S Sejati, A Imbert, C Gérardin, S Dumarçay, E Fredon, E Masson, D Nandika, T Priadi, P Gérardin

Effect of Furfurylation on Shear Strength of Bond Line and Screw Withdrawal Resistance of Beech and Fir Wood
2016 - IRG/WP 16-40757
The aim of this study was to investigate the effects of furfurylation on shear strength of bond line and screw withdrawal resistance of beech (Fagus orientalis) and fir (Abies alba) species. In this regard, specimens with two different values of furfurylation i.e. low (fir 14% and beech 20%) and high (fir 38% and beech 65%) levels were prepared and evaluated in comparison with untreated specimens. The furfurylation was performed after impregnating the specimens by furfuryl alcohol under vacuum condition followed by heating duration to complete polymerization and crosslinking. Specimens were prepared according to standard ASTM D 905 in order to assess shear strength of bond line formed with three different types of adhesives, single-component polyurethane, polyvinyl acetate as well as urea-formaldehyde. Also screw withdrawal resistance of wood polymer specimens was measured perpendicular to grain and parallel to grain. The results indicated that the shear strength of the bond line decreased and screw withdrawal resistance increased by furfurylation level. Examination of adhesion mechanism demonstrated that formation of an appropriate interface between water-soluble adhesives and wood-polymer involves effective penetration of adhesive into cell wall. Hence, the interface of adhesives and material would be the determining factor in developing strength of adhesive joints. Since the wood-furfuryl alcohol is a cell-wall wood-polymer, the possibility of creating an appropriate interface by increasing of furfurylation level was impaired. On the other hand, the adhesion mechanism of polyurethane glue compared to water-soluble adhesives such as polyvinyl acetate and urea-formaldehyde is significantly different, therefore exhibited more strength. The withdrawal screw resistance of furfurylated wood was increased by furfurylation level due to changing nature of wood and increasing shear strength of wood-polymer. This gain was also more evident in fir than beech. The results showed that screw withdrawal resistance perpendicular to grain was higher than parallel to grain.
A Talaei, H Abdolzadeh, M Saleh Zare

Effect of different concentration of furfurylation on physical properties and decay resistance of Paulownia wood
2016 - IRG/WP 16-40762
The furfurylation process is an extensively investigated wood modification process. Penetration of Furfuryl alcohol molecules into the wood cell wall results in a permanent swelling. In the present study, different concentrations effect of furfuryl alcohol monomer on physico-biological properties such as water uptake, dimensional stability and decay resistance of wood polymer made by fast-growing Paulownia wood were investigated. Wood-polymer composites were prepared by vacum-pressure impregnation of furfuryl alcohol in 20, 40, 60, 80 and 100% concentrations including ethanol for dilution, maleic anhydride and citric acid as catalyst. According to the results, weight percent gain of furfuryl alcohol levels was determined as 22.08, 45.82, 71.17, 87.48 and 101.43 % corresponding to 20, 40, 60, 80 and 100% concentrations, respectively. It was found that the increase of concentration led to significant improvement in dimensional stability and decay resistance and reduction in water uptake of composite. Furfuryl alcohol improved significantly resistance to Trametes versicolor, resulted in decreasing weight loss. The present study found no difference in the amount of improvement between decay resistance from furfurylated wood in 80 and 100% concentration. Furfurylation of Paulownia wood shows an interesting potential to improve the wood quality for solid timber products.
M Ghorbani, H Asghari

Corrosion of fasteners in furfurylated wood – final report after 9 years exposure outdoors
2017 - IRG/WP 17-40810
The corrosion of some common fastener materials – mild steel, stainless steel, zinc-coated steel, brass and Sanbond Z (nickel, zinc and chromate) coated steel – has been evaluated after nine years exposure outdoors in untreated Scots pine and furfurylated beech and southern yellow pine (SYP). The furfurylation was carried out according to a process that resulted in approximately 40 % WPG (Weight Percent Gain). The results show that the corrosion of fasteners in furfurylated wood according to the particular specification is considerably more severe than in untreated wood and very similar to the corrosion caused by thermally modified wood. Mild steel and zinc coated steel has been most susceptible. Stainless steel has not been attacked at all and is therefore strongly recommended for furfurylated wood in outdoor applications.
J Jermer, B-L Andersson, J Schalnat

Effect of furfurylation treatment on the performance of three Canadian wood species
2022 - IRG/WP 22-40925
The demand for exterior wood siding is stagnating in North America, partly due to the perception of consumers, architects and contractors regarding their durability and maintenance. Improving attributes such as the dimensional stability of wood is therefore necessary to make it more attractive to consumers. This project aims to assess the performance of Canadian species; white spruce (Picea glauca), trembling aspen (Populus tremuloides) and jack pine (Pinus banksiana) treated by furfurylation. Anti-swelling efficiency (ASE), when exposed to humidity increased by an average of 40 % for white spruce, 44 % for aspen and 27 % for jack pine. In immersion, the furfurylation treatment increased ASE up to an average of 43 % for white spruce, 35 % for aspen and 18 % for jack pine. Modified Brinell and Janka hardness were increased for the furfurylated white spruce and especially furfurylated aspen. Furfurylated wood species showed a high whitening after accelerated UV exposure. However, this color change was reduced by applying a semi-transparent stain on the treated samples. Furfurylation treatment of Canadian wood species shows an interesting potential to improve their performance.
G Boivin, D Schorr

Molecular dynamics investigation of wood modification with furfuryl alcohol
2022 - IRG/WP 22-40931
Molecular dynamics (MD) was applied to investigate and understand the structural characteristics and the interaction of cellulose and lignin with furfuryl alcohol for explaining the wood modification process. A single chain of cellulose polymer model and a softwood lignin model was considered to represent cellulose and lignin polymers. The obtained radial distribution function results revealed that cellulose and lignin are equally interact with furfuryl alcohol and no significant difference was observed in the case of solvent accessible surface area results. The interaction energy was calculated from the contribution of Van der Waals and electrostatic interaction and the results revealed that cellulose showed a strong interaction with FA than lignin model. The hydrogen bonding analysis demonstrated that the lifetime of hydrogen bonds involved between cellulose-FA and lignin-FA exhibit similar values which facilitate same interaction. The principal component analysis demonstrated that lignin undergoes a large motion in term of conformational space than cellulose due to highly heterogenous structure of lignin and cellulose polymer chain tend to form linear confirmation in FA. This work suggested that furfuryl alcohol equally bound to cellulose and lignin during furfurylation of wood, and the detailed investigated data provides the interaction mechanism of furfuryl alcohol treatment of wood to some extent.
V Ponnuchamy, J Sandak, A Sandak