Mats Westin

Properties of furfurylated wood

The first processes of wood modification with furfuryl alcohol (FA) (furfurylation) were developed several decades ago. FA is a renewable chemical, produced from hydrolysed biomass waste. Over the past decade modernized processes for furfurylation of wood have been developed. This study presents decay properties of furfurylated wood. Laboratory methods and field tests were performed on fungi, termite and marine borer attack. Tests on physical and mechanical properties are also presented. The properties of furfurylated wood depend on the retention of grafted/polymerized poly-FA in the wood. At high modification levels (high retention of poly-FA) the enhancement of a wide variety of properties is achieved: an exceptional increase in hardness, exceptional resistance to microbial decay and insect attack, increase in modulus of rupture (MOR) and modulus of elasticity, and high dimensional stability. At lower modification levels property enhancements also occur. Notable are resistance to microbial decay and insect attack, and relatively high dimensional stability.

Towards novel wood-based materials: Chemical bonds between lignin-like model molecules and poly(furfuryl alcohol) studied by NMR

Abstract Wood modification with furfuryl alcohol is a non-toxic alternative to conventional preservation treatments. A process in which furfuryl alcohol polymerises in situ was previously proposed for chemical modification of wood. In the present work, liquid model systems were investigated using compounds that resemble repeating units of lignin to verify whether chemical bonds form between the furfuryl alcohol polymer and wood. Using different NMR spectroscopic techniques we confirmed that these model compounds do form covalent bonds with the polymerising polymer. The results indicate that the furan polymer grafts to lignin, supporting observations in similar studies performed with genuine wood materials.

Chemistry and ecotoxicology of furfurylated wood

Over the past decade modernized processes for furfurylation of wood have been developed. These new processes are based on completely new catalytic systems and process additives. These new systems do not add metals or halogens to the product, which is important for an environmentally acceptable product. However, little is known about the ecotoxicity of furfurylated wood or other environmental impacts that may result from the modification method. The study shows that concentrations of non-reacted furfuryl alcohol in the final products are low and do not contribute to any fungicidal effect. Environmental tests show no significant level of increased ecotoxicity, and degradation through combustion does not release any volatile organic compounds or polyaromatic hydrocarbons above normal levels for wood combustion. Hence, furfurylation of wood to enhance wood properties is not believed to be harmful to the environment.

Eco-efficient wood protection: furfurylated wood as alternative to traditional wood preservation.

This paper aims to show the potential decay resistance of furfurylated wood and investigate possible eco‐toxicity of such materials produced. This paper deals with the environmental aspects and durability of furfurylated wood, both laboratory and field tests are included in the investigations. Results from several decay tests, emission analysis studies and ecotox tests are presented. The results show that furfurylated wood is highly decay resistant. Furthermore, no significant increase in eco‐toxicity of leaching water was found and degradation through combustion does not release any volatile organic compounds or poly‐aromatic hydrocarbons above normal levels for wood combustion. Durability enhancement by furfurylation of wood is not believed to be harmful to the environment. Wood modified with furfuryl alcohol, “furfurylated wood”, is currently being marketed as a non‐toxic alternative to traditional preservative treated wood (wood impregnated with biocides). This paper summarises much of the long term exposure of furfurylated wood ever caried out, and present the first eco‐tox tests on such material ever done.

Development of Modified Wood Products Based on Furan Chemistry

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, produced from hydrolysed biomass waste. Over the last decade modernised processes for furfurylation of wood have been developed. These new processes are based on completely new catalytic systems and process additives. 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 and 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 and MOE, and relatively high dimensional stability. Two main processes for production of furfurylated wood have been developed for Kebony ASA (Former Wood Polymer Technology ASA) by the authors. Kebony TM for hardwood modification and VisorWood TM for soft wood modification, where the name reflects the colour of the material produced by the process. Commercial production according to the Kebony process has been running since October 2003, mainly for flooring. A small Kebony production plant is now in operation in Lithuania. A Kebony/VisorWood production plant was started during of 2003 in Porsgrunn, Norway. There are now planed for an expansion of this plant, and plans for a large Visorwood plant is ongoing. Further commercialisation of the technology will be done through licences issued by Kebony ASA.

Field test of resistance of modified wood to marine borers

Abstract The resistance of modified wood to marine borer attack was tested in a field test according to the European Standard EN 275. The wood modification methods were: 1) furfurylation; 2) treatment with methylated melamine resin (MMF); 3) acetylation; 4) acetylation followed by furfurylation; 5) acetylation followed by treatment with MMF resin; 6) maleoylation (using water solution of MG, maleic anhydride esterified glycerol, or organic solvent solution of maleic anhydride); 7) succinylation (with or without post-treatment with copper sulphate solution); 8) modification with reactive linseed oil derivative; 9) treatment with modified rape seed oil; 10) thermal modification in nitrogen gas (Le bois retifié); 11) thermal modification in fresh rape seed oil; and 12) thermal modification in modified rape seed oil. The wood species used for all treatments was Scots pine. The test specimens were put on the test rigs in a bay on the Swedish west coast. The marine borer (mainly Teredo navalis) activity at the test site is very high, always resulting in failure of control specimens within a year. Many of the modification methods result in modified wood with poor resistance to marine borers. In some cases the modified wood samples seemed even more severely attacked than the controls. However, some of the methods (furfurylation, MMF-treatment, and acetylation followed by MMF-treatment) seem to provide excellent resistance to borer attack.

Toxic hazard and chemical analysis of leachates from furfurylated wood

The furfurylation process is an extensively investigated wood modification process. Furfuryl alcohol molecules penetrate into the wood cell wall and polymerize in situ. This results in a permanent swelling of the wood cell walls. It is unclear whether or not chemical bonds exist between the furfuryl alcohol polymer and the wood. In the present study, five different wood species were used, both hardwoods and softwoods. They were treated with three different furfurylation procedures and leached according to three different leaching methods. The present study shows that, in general, the leachates from furfurylated wood have low toxicity. It also shows that the choice of leaching method is decisive for the outcome of the toxicity results. Earlier studies have shown that leachates from wood treated with furfuryl alcohol prepolymers have higher toxicity to Vibrio fischeri than leachates from wood treated with furfuryl alcohol monomers. This is probably attributable to differences in leaching of chemical compounds. The present study shows that this difference in the toxicity most likely cannot be attributed to maleic acid, furan, furfural, furfuryl alcohol, or 2-furoic acid. However, the difference might be caused by the two substances 5-hydroxymethylfurfural and 2,5-furandimethanol. The present study found no difference in the amount of leached furfuryl alcohol between leachates from furfurylated softwood and furfurylated hardwood species. Earlier studies have indicated differences in grafting of furfuryl alcohol to lignin. However, nothing was found in the present study that could support this. The leachates of furfurylated wood still need to be

The combined effect of wetting ability and durability on outdoor performance of wood: development and verification of a new prediction approach

Comprehensive approaches to predict performance of wood products are requested by international standards, and the first attempts have been made in the frame of European research projects. However, there is still an imminent need for a methodology to implement the durability and moisture performance of wood in an engineering design method and performance classification system. The aim of this study was therefore to establish an approach to predict service life of wood above ground taking into account the combined effect of wetting ability and durability data. A comprehensive data set was obtained from laboratory durability tests and still ongoing field trials in Norway, Germany and Sweden. In addition, four different wetting ability tests were performed with the same material. Based on a dose–response concept, decay rates for specimens exposed above ground were predicted implementing various indicating factors. A model was developed and optimised taking into account the resistance of wood against soft, white and brown rot as well as relevant types of water uptake and release. Decay rates from above-ground field tests at different test sites in Norway were predicted with the model. In a second step, the model was validated using data from laboratory and field tests performed in Germany and Sweden. The model was found to be fairly reliable, and it has the advantage to get implemented into existing engineering design guidelines. The approach at hand might furthermore be used for implementing wetting ability data into performance classification as requested by European standardisation bodies.

Ecobuild a Center for Development of Fully Biobased Material Systems and Furniture Applications

There is a great incentive and motivation in the building and wood research communities as well as in the industry to develop more eco-efficient and durable wood-based products with better performances. In this context, eco-efficient products refer to “green” sustainable products where both economical and ecological aspects have to be balanced. This presentation will give the general strategies within the newly formed Swedish Institute Excellence Center, EcoBuild. The conceptual idea for this competence centre is a conversion of biomass into innovative, eco-efficient and durable wood based products. The vision is that EcoBuild will, through the formation of a university-institute-industry cooperation, act as an international leading innovation, research and technology development platform within the wood science and technology field. The research projects within the centre are guided by a group of about 30 industry partners and also by end-user demands (Fig. 1). Types of materials in focus are: modified solid wood such as heat treated, furfurylated and acetylated wood, biobased binders and coatings, and biocomposites. A top priority is to develop fully biobased products, i.e., all raw materials should preferably be biobased, including chemicals for modification, adhesives, and surface treatment. Aspects and initial results regarding some of the EcoBuild activities will also be presented. Examples of research projects already started are: 1) Novel bio-based board resins; 2) UV-resistant clear coatings for exterior use; 3) Highly durable WPCs for outdoor use based on modified wood particles; 4) Modification of hardwood for exterior applications; 5) Fundamental understanding of the mechanisms involved in the durability of modified wood. FIGURE 1 The integrated research areas within Institute Excellence Center, EcoBuild.

Combined evaluation of durability and ecotoxicity: A case study on furfurylated wood

Abstract Modified wood is commercially available and merchandized as a new, environmentally friendly and durable wood species. However, there are no standards focusing on the evaluation of modified wood. Combining resistance against fungal decay and good ecotoxicological properties may be a start. In this study softwood and hardwood species were furfurylated using different treatment processes and treating solutions. The durability was determined by exposing the treated wood to a range of Basidiomycetes and the ecotoxicity was studied on two aquatic organisms. It was the purpose to come to a strategy and how to unite efficacy and ecotoxicity, since this is important in product development. The results show that the selection of fungus used for mass loss determination and the choice of ecotoxicity method is decisive, confirming that a combination of methods is valuable. A tiered approach to find the optimal treatment seems the best option. First, adequate protection against wood-rotting fungi should be attained, followed by ecotoxicity evaluation of the wood leachates. If necessary, the optimization process should be repeated until both durability and ecotoxicity are within satisfactory limits. This process could be extended with other evaluation criteria, e.g. dimensional stability of the modified wood or a risk analysis of its leachate.