Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
PIBOLEO project: Eco Innovative process for multi-functional bioleothermal treatment for wood preservation and fire proofing Frédéric Simon1, Laurence Podgorski1, Jean-Denis Lanvin1, Marie-France Thévenon2, Henri Baillères2, Sandra Warren3 1
Institut Technologique FCBA, Allée de Boutaut, B.P. 227, 33028 Bordeaux Cedex, France e-mail :
[email protected]
2
CIRAD PERSYST – UPR 40, Laboratoire de Préservation des Bois, TA B-40/16, 73, rue Jean François Breton, 34398 Montpellier Cedex 5, France e-mail :
[email protected]
3
ITERG Institut des Corps Gras, 21 Rue Gaspard Monge, Parc Industriel Bersol, 33600 Pessac, France e-mail :
[email protected]
Keywords: Wood modification, linseed oil functionalization, durability, reaction to fire, weathering, UV protection, technology transfer
ABSTRACT This paper presents the latest research project supported by the French research agency ANR regarding the bi-oleothermal treatment of wood at atmospheric pressure. Wood treatment by the "bi-oleothermal" process (combination of oil and heat treatment) is a well mastered alternative method for wood protection. The interest of this multi-functionnal process is to allow wood drying as well as wood treatment in a single step process. Nevertheless, there is still a need to work on the formulations of the oils used in order to adapt the performance of the treated wooden material (durability towards wood destroying organisms, fireproofing, etc...) to its enduse. Moreover, due to its alternative process, the up-grading and use of local timbers in new enduses become possible and remain also one of the main objectives of this project. A large and precise environmental analysis (including life cycle assessment) will be also carried out during this project, for all stages of the process : from the oil formulations to the end of the life time of treated timbers. The main steps of this project can be mentionned as follow: - process optimization by eco additives selection and linseed oils fonctionnalization - multi scale process optimization, from lab to industrial plant - grafting lab analysis on wood fibers - environmental and societal analysis from the process to the treated timbers INTRODUCTION The bi-oleothermal treatment In France a simple bi-oleothermal© process is currently developed by CIRAD and FCBA in order to make wood more stable and less sensitive when used outdoors.This two stage process operates at atmospheric pressure and uses two oil baths, as described in Fig. 1.
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
HEATING
TRANSFER
TEMPERING
(from a few seconds to several hours)
Hot bath - Oil at 110-200°C
« fast » with specific device
- Duration according to volume
Cold bath - Solution at 10-90°C - Variable duration
Green state or dried wood
1
110-200°C
2
3
10-90°C
Figure 1: The bi-oleothermal process – 3 different steps
The first stage consists in dipping the wooden piece in a hot oil bath (between 110°C and 200°C, usually close to 140°C) for the duration necessary to reach the moisture content of the targeted end-use. During the first stage, the pressure inside the wood cells increases due to the wood moisture content on one hand, but also to the increasing temperature on the other hand. Then, during this step, the water located in the wood lumens vaporizes, starting from the outside part of the wood pieces and this phenomenum moves to the central part of the wood piece. At the end of this first stage the wood may contain a significant volume of vapour, depending on the dipping stage duration, which is not homogeneous inside the wood piece. Then the sample is quickly moved to the second bath where it is dipped for a few minutes in oil between 20°C to 80°C. Since the second bath contains oil at a temperature lower than the boiling temperature of water, the wooden sample cools what leads to water condensation. A vacuum is created inside the sample and makes the oil to impregnate the wood deeply. The process and the influence of the treatment parameters on heat and mass transfer, the thermo-dynamical phenomena, have been reported by Grenier (Grenier et al. 2003, Grenier 2006, Grenier et al. 2007). This process offers several advantages: - it is very simple and operates at atmospheric pressure; - it may contribute to save money since it allows the use of green wood: a fast drying is performed during the first stage; - a deep oil impregnation is achieved; - the equipment is cheap and easy to use, it may allow the recycling of vegetable oils. Resistance to fungi and insects, resistance to weathering and fire reaction of treated wood: State of the art for the bi-oleothermal treatment Different studies have been performed in the last past years by FCBA and CIRAD to evaluate the potential of this type of treatment for wood preservation, resistance to weathering and fire reaction (Podgorski et al. 2007, 2008).
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
For example, the protective effectiveness of oil treatments against wood destroying basidiomycetes was tested using five types of oils: - H1 is a drying linseed oil, - H2 is a maleinized drying linseed oil, - H3 is H2 + 0.6% propiconazole + 0.3% permethrin, - H4 is H2 + 1% propiconazole +0.3% permethrin, - H5 is H3 with a UV absorber. The protective effectiveness of oils treatments against termites and longhorn beetles was tested using two types of oils: H1 (same as above), HB is the same than H1 and includes an insecticide (0.3% permethrin). The weatherability of oils treatments was studied on oak samples using H2 and H5. The impregnation of the samples with the different oils were performed by CIRAD using the bioleothermal process. The typical conditions were 10 minutes in the hot oil bath (rape oil at 150°C) and 5-10 minutes in the second bath at 60°C (with Hn). H1 was used to impregnate samples subjected to reaction to fire. Protective effectiveness of oil treatments against wood destroying Basidiomycetes The weight percent gain (mean and coefficient of variation CV) caused by uptake of oil during the treatment is shown in Table 1 and shows that the oil uptake is a little bit higher in pine than in beech, and strongly different for oak with more deviation. Table 1: Weight percent gain caused by uptake of oil Wood sp Mean CV Pine 36% 13% Beech 30% 15% Oak 11.9% 51%
The moisture content of the treated samples (mean and coefficient of variation) at the end of exposure to fungi is presented in Table 2 and compared to the moisture content of the untreated samples. This table shows that the oil treatment leads to an important decrease in the moisture content at the end of fungal exposure. Table 2: Mean and coefficient of variation of the moisture content of the treated and untreated samples Wood sp Treatment Mean (%) CV (%) Pine Oil treated 23.9 30 Untreated 57.8 21 Beech Oil treated 26.0 14 Untreated 54.9 50
The mean mass loss of specimens treated with the different oil treatments and exposed to fungi was calculated for both weathering methods. For each oil treatment the maximum of the mean mass loss is presented in Table 3 for the 2 accelerated ageing method used: the V313 method according to the EN 321 standard and the wheel method (FCBA procedure). Table 3: Maximum of the mean mass loss for both accelerated ageing V313 Wheel Oil treatment Max mass loss(%) Fungus Max mass loss (%) Fungus H1 20.8 Coniophora puteana 17.6 Coriolus versicolor H2 12.1 Coniophora puteana 14.1 Coriolus versicolor H3 8.3 Coniophora puteana 8.6 Coniophora puteana H4 3.3 Gloeophyllum trabeum 6.0 Gloeophyllum trabeum H5 5.9 Gloeophyllum trabeum 10.4 Coniophora puteana
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
The efficacy of the different oils to protect wood against basidiomycete fungi can be classified as follows: H4 > H5 = H3 > H2 > H1. The protective efficacy is especially linked to the amount of propiconazole. As expected the lowest efficacy is obtained with the oils without any biocides (H1 and H2). However these oils improve the resistance of wood since they lead to a decrease in the mass losses compared to the untreated samples (see Table 6). Compared to natural oil, the maleination process significantly improves the resistance against basidiomycete fungi. For the different treatments the mass losses are higher than 3%. Therefore, according to EN 113 and EN 599 specifications, the oil treatments tested are not effective enough to protect wood against basidicomycete fungi. However the mass losses of pine samples can be examined using the method described in the technical specification CEN/TS 15083-1 (2005). For beech species tests the same procedure was used (see Table 5) with Coriolus versicolor only.
Oil H1 H2 H3 H4 H5
Table 4: Pine - Median mass loss (%) after 2 different accelerated ageing methods Coniophora Poria placenta Higher median Durability class according to puteana mass loss Annex D of CEN/TS 15083-1 Wheel V313 Wheel V313 Wheel V313 Wheel V313 11.1 19.2 11.9 12.5 11.9 19.2 3 4 8.7 12.0 10.6 10.0 10.6 12.0 3 3 9.0 9.6 1.3 7.4 9.0 9.6 2 2 3.2 0.9 1.1 2.7 3.2 2.7 1 1 12.3 0.8 0.9 2.7 12.3 2.7 3 1
Table 5: Beech - Median mass loss (%) after accelerated ageing (wheel or V313 cycle) Wheel method V313 cycle Durability class Durability class according to according to Coriolus versicolor Coriolus versicolor Annex D of Annex D of Oil CEN/TS 15083-1 CEN/TS 15083-1 3 H1 17.6 4 14.9 2 H2 14.7 3 7.9 2 H3 5.1 2 6.7 1 H4 3.7 1 3.4 1 H5 5.3 2 2.5 Table 6: Median mass loss (%) and durability class of untreated wood Fungus Pine Beech Coniophora puteana 31.6 Poria placenta 33.2 Gloeophyllum trabeum 31.9 Coriolus versicolor 34.4 Durability class 5 5
For both species results show (Table 4 and 5) that treatments with biocide-free oils (H1 and H2) increase the durability (durability class 3 or 4) compared to untreated wood (Table 6). A better durability is obtained with the addition of biocides. The artificial ageing according to the V313 cycle seems to be less severe than the ageing with the wheel. The addition of a UV absorber does not increase the performance. The maleinized oil displays better results than natural oil.
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
Protective effectiveness of oil treatments against insects Oil treated wood is not completely efficient against the insects tested, house longhorn beetles and termites. These insects are capable of boring the wood, but this material as a unique source of nutrition does not allow their survival. Nevertheless, an insecticide needs to be added to protect the wood effectively. When an appropriate dose of insecticide is added to the oil there is no survival in the test device and no degradation of the wood and the performance is that of usual preventive wood treatments against wood boring insects. In EN 47 and EN 117 tests, untreated wood and treated wood samples are separately tested. In order to gain more knowledge about the effect of oils it would be interesting to perform extra test where untreated and oil treated samples are tested in the same test device. This would give clearer information about the behaviour and the choice of the insects facing the oil treated wood. Fire reaction of oil treated timbers It is expected that oil treatments may have a negative impact on wood subjected to fire. That is why the influence of the oil treatment on wood exposed to fire was studied on oil treated samples and on samples which were fireproofed and then oil treated. Two types of tests were carried out: the single-flame source test according to EN ISO 11925-2 and the the Single Burning Item test according to EN 13823. The single-flame source test shows that the oil treated samples do not pass the test and have a fire classification F. Better results are obtained on samples that have been fireproofed and then impregnated with the linseed oil. In this case the samples pass the test and a fire classification E is obtained. This classification is not affected by one year of natural weathering. The Single Burning Item test was performed on samples which passed the single-flame source test, that is to say on samples which were fireproofed then oil treated. The fireproofed then oil treated samples fulfil the fire classification C requirements before weathering which is better than the fire classification of bare wood (without any treatment). After one year of natural weathering the samples show a fire classification D due to an increase in the FIGRA values. The natural weathering probably leads to a leaching of the phosphate salts at the wood surface. However the THR values stay in the zone of the fire classification B grading. This indicates that the weathered samples are still protected against fire and that the bi-oleothermal treatment limits the loss of fire retardants salts due to the natural weathering. Oil treated samples
Fireproofed and oil treated samples
Figure 1: Single-flame source test results on non-weathered samples
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
All the results mentioned previously show that bi-oleothermal treatment might be a complementary method for wood preservation against fungi and insects and might be a good way to keep the fire retardants salts inside the wood during natural weathering. PIBOLEO PROJECT Subsequently, the PIBOLEO project (Multi-functional eco-innovative Bi-oleothermal process of timber preservation and fireproofing) was built to allow research centres and industrial partnership to work on oils and eco-additives to find the right solutions for the wood used in timber construction according to its end-uses conditions. As the treatment process is well mastered for many sorts of wood species, it was decided now to work on the oils used during the process. The oil should be designed according to the use of the wood in construction, and can be different according to the wood species, the end-use (cladding, decking…) because the durability and regulation requirements can be strongly different. The PIBOLEO project includes the following partnership: - FCBA, CIRAD and LERMAB as wood research centers. - ITERG which is the French technical center on oils - Vandeputte Oleochemicals, company specialized in the production of linseed oils - Oléobois, a French SME specialized on the design and installation of oleothermal wood treatment plants - Génération Bois, a French SME which actually uses the industrial prototype of bioleothermal treatment of wood designed by the CIRAD researchers. Added to technical points from this multi scale analysis, one special focus will be performed for studying a complete environmental and societal analysis from the process to the treated timbers and the eventual grafting phenomena on the wood components. This project started in February 2008, and after a complete state of the art on the subject, the next step is to work on the oil baths. 1ST STEP: NATURE OF OIL BATHS Whereas the first oil bath helps dry out the wood, the goal of the second oil bath is to actually treat the wood. The oil present in the second oil bath gets wicked into the pores of the wood, along with any additives which may be present. The nature of the second oil bath and of the additives is critical since they are responsible for the properties of the final product (wood with the desired characteristics and proper resistance to fire, insects, fungi, UV, etc). The PIBOLEO project is currently focusing on fire-retardant additives and biocides (fungicides, insecticides, etc). These additives need to be as environmentally acceptable as possible. Formulation of the second oil bath The nature of the oil that is to be used in the second bath is obviously of paramount importance. While the oil should dry as quickly as possible in order to make the wood treatment more practical industrially, it must also have good oxidative stability, so that the oil can be used for as many batches as possible. Special attention must be paid to this factor, since the oil will spend quite some time at temperature above ambient under normal operating conditions, with possible contamination from the wood itself and from the first oil bath. Linseed oils usually are good candidates for this application since they contain a lot of unsaturations (a typical linseed oil contains 50 to 70% of linolenic acid) which allow for quick drying of the wood. However, these unsaturations can also cause oxidation issues.
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
In order for the process to be useful, the additives (fire-retardants, biocides) selected for the wood treatment must be soluble in the oil selected, so that they can be absorbed into the wood at the same time as the oil and impart the desired properties. These additives can also be introduced in the form of chemically modified or grafted oil, so as to provide optimal miscibility with the oil. This is one of the aspects being worked on within the PIBOLEO project. However, chemical modification of the biocides implies filing for an authorization in order to comply with the biocide regulations. Use of an emulsion as the second bath In order to facilitate the selection of fire retardant and biocide additives, it is possible to use an emulsion as the second bath of the wood treatment. Although the requirements for the oil being used remain unchanged, the use of an emulsion permits the use of additives which are watersoluble. This results in a much wider selection of additives available (unfortunately, this may impact negatively the aging properties because of the additives being washed out of the wood). Surfactants are then necessary to stabilize the water-in-oil (W/O) emulsion. Some of the additives selected among the fire-retardants or biocides may act as surfactants. A real issue with the emulsion option is the stability of the emulsion through the temperature changes and pollution from the first bath (wood extractives, water, oil from the first bath, etc). Recycling of the bath may also be problematic. Obviously, the amount of water used in the emulsion should be as small as possible so as to avoid reintroducing too much water into the wood, which would be detrimental to wood preservation. In this kind of system, the choice of the surfactant is paramount. This choice can be guided by the Hydrophile Lipophile Balance (HLB) system (Griffin 1949, Griffin 1954). In this system, the various surfactants are ranked according to their relative hydrophilic and lipophilic components. In the case of W/O emulsions, the desired HLB surfactant is ranking between 4 and 6. Work plan The presence of industrial partners within the PIBOLEO project emphasizes the importance of the industrial viability of the improved wood-treatment process. Therefore, the issues susceptible to arise industrially must be addressed as early as possible at the laboratory scale. The first possible problems come from the first oil bath, which must withstand rather drastic conditions: relatively high temperatures for an extended time, addition of water, wood extractives, etc during the dipping of the wood. The stability of the oil over time will be studied by various techniques: - The peroxide index (according to Regulation EEC 2568/91 - Annex III, chloroform method) will give an indication of the oxidation of the oil - The water content will give an idea of the pollution of the oil by the wood. Once the water content gets too high, the efficiency of the wood treatment could decrease. - The viscosity will indicate whether polymerization of the oil is occurring (when the bath gets too viscous, the efficiency of the wood treatment may be unsatisfactory). The stability of second oil bath will also be investigated for different levels of the various additives. In the case where the oil is formulated with active substances, the same parameters as indicated above for the first oil bath will be followed over time (peroxide index, water content, viscosity). The stability and solubility of the various additives in the linseed oils will be checked over time. Another point of interest will be whether the used bath can be recycled by mixing with a fresh batch while still getting good properties for the treated wood.
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
When an emulsion is used as the second oil bath, the first parameters studied will be the mixing speeds and times during the emulsification step. In the laboratory, a Rayneri mixer will be used. Different levels and combinations of the various active substances will be considered, as they can impact the stability of the emulsions. Different combinations of surfactants at various levels and different linseed oils will be compared as well. In a first step, the viscosity of the emulsion at the operating temperature selected for the second bath and its evolution over time will be studied (a high viscosity of the emulsion can impede the wicking process). Then, the relative stability of the various emulsions will be compared by Lumifuge at the operating temperature selected for the second bath. The Lumifuge allows for accelerated aging of the emulsions via centrifugation, while checking the light transmission profile of the emulsion sample (thus indicating whether separation of the phases is occurring). This study will not take into account the influence of the thermal shock and pollution from the wood on the stability of the emulsions, or the recyclability of the emulsions. These points will be investigated by small-scale trials in the laboratory. These small scale trials will involve actual treatment of small wood samples and will allow for actual testing of the wood samples (dimensional stability, appearance, chemical analyses for estimating the quantities of active substances present in the wood sample, resistance to fire, fungi, insects, and aging). NEXT STEPS, PERSPECTIVES AND CONCLUSION The technical performances of both the process itself and the treated timbers will be evaluated for these 2 options for the 2nd oil bath: (1) the active ingredients are in emulsion in the bath oil, (2) the bath oil is made of functionalized oil (linking with the active ingredients). Prior to the standardized biological tests, screening tests will be performed as soon as the emulsions and functionalized oils are developed. The screening tests, on pine sapwood as a model, will be restricted to two types of organisms: (i) Basidiomycete fungi: Coniophora puteana, Gloeophyllum trabeum and Poria placenta. The method will be adapted from Bravery (1979) considering the recommendations of Unga and Militz (2005); (ii) Termites: Reticulitermes santonensis. These tests will be performed according to Thevenon et al. (2003). Tests on treated pine sapwood will also be done in order to investigate the fire reaction of such treated timber. These preliminary tests will allow to choose the best options for biological efficiency and fire retardancy, and only 2 emulsions and 2 functionalized system will remain to carry on this study. Scots Pine, Maritime pine and Beech will be treated on a larger scale and the performances of treated timbers will be evaluated: - retention and penetration of both oil and active ingredients will be determined using adequate chromatography or inductively coupled plasma (ICP), and performances of the treatment will be established following the guidelines of NF 50-105-3; - accelerated aging : QUV according to the EN 927-6 and V313 according to EN 321 prior to the biological tests. Some of the aged blocks will be used to determine the remaining oil and product retentions and distribution. - biological tests according to EN 47, EN 117, EN 113; - fireproofing according to EN 13823 and ISO 11925-2; - eco-toxicological tests (to be determined).
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
Beyond this technical validation of the process, the environmental and economical performances will also be evaluated, in order to allow the timber products produced to find a suitable place on the market. ACKNOWLEDGEMENTS Special thanks to the National Agency for Research (ANR - ADEME) for funding. REFERENCES Bravery, A. (1979) A miniaturised wood-block test for the rapid evaluation of wood preservative fungicides. In: Report of the Swedish Wood Preservation Institute, II-Screening fungicide, Paper 8, pp. 57-65. CEN/TS 15083-1 (2005) Durability of wood and wood-based products - Determination of the natural durability of solid wood against wood-destroying fungi, test methods - Part 1: Basidiomycetes EN 47 (2005) Wood preservation products. Determination of the toxic values against larvae of Hylotrupes bajulus (Linnaeus). Laboratory method. EN 113 (1996) Wood preservation products. Method of test for determining the protective effectiveness against wood destroying basidiomycetes. Determination of the toxic values. EN 117 (2005) Wood preservation products. Determination of the toxic values against Reticulitermes (European termites). Laboratory method. EN 321 (2002) Wood based panels. Determination of moisture resistance under cyclic test conditions. EN 927-6 (2006) Paints and varnishes. Coating materials and coating systems for exterior wood. Part 6: exposure of wood coatings to artificial weathering using fluorescent UV lamps and water. EN 13823 (2002) Reaction to fire tests for building products - Building products excluding floorings exposed to the thermal attack by a single burning item Grenier, D. (2006) Développement du procédé de bi-oléothermie pour les bois de construction: mesure et modélisation des transferts de matière et de chaleur lors des opérations de fritureséchage et de refroidissement-imprégnation. Thesis of the University of Perpignan (F), 181 p. in French. Grenier, D., Baillères, H., Méot J-M., Langbour P., Lanvin J-D. (2003) A study of water loss and oil absorption during oleothermic treatment of wood. In: Proceedings of the First European Conference on Wood Modification. Ghent, Belgium, pp 23-32. Grenier, D., Bohuon, P., Méot, J-M., Lecomte, D., Baillères, H. (2007) Heat and mass transfer in fry drying of wood. Drying Technology, 25, pp. 511-518.
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Cost Action E37 Final Conference in Bordeaux 2008 Socio-economic perspectives of treated wood for the common European market
Griffin, W. C. (1949) Classification of Surface-Active Agents by ‘HLB’. Journal of the Society of Cosmetic Chemists, 1, pp. 311. Griffin, W. C. (1954) Calculation of HLB Values of Non-Ionic Surfactants. Journal of the Society of Cosmetic Chemists, 5, pp. 259. ISO 11925-2 (2002) Reaction to fire tests for building products - Part 2: Ignitability when subjected to direct impingement of flame NF 50-105-3 (2008) Durability of wood and wood-based products. Preservated treated massive wood. Part 3: Wood preservation performance and treatment certificate. Adaptation to France metropolitan territory and French overseas territories. Podgorski, L., Le Bayon, I., Paulmier, I., Lanvin, J.D., Georges, V., Grenier, D., Baillères, H., Méot, J.M.. (2008) Bi-oleothermal treatment of wood at atmospheric pressure: resistance to fungi and insects, resistance to weathering and reaction to fire results. International Research Group on Wood Protection, 39th annual meeting, Istanbul Turkey, 25-29 May, document IRG/WP 08-40418, 16 p. Podgorski, L., Le Bayon, I., Paulmier, I., Lanvin, J-D., Grenier, D., Baillères, H., Méot, J-M. (2007) Bi-oleothermal treatment of wood at atmospheric pressure: biological properties, weatherability, paintability. In: Proceedings of the Third European Conference on Wood Modification Cardiff, (United Kingdom), 15-16 October, pp. 87-97. Thévenon, M.F., Simonin, P., Carrère, A., Fouquet, D. (2003) Evaluation of Rosewood extractives as potential source for termite control. The International Research Group on Wood Protection, Doc IRG/WP03-30323. Unga, U. and Militz, H. (2005) Particularities in agar block tests of some modified woods caused by different protection and decay principles. In: Proceedings of the second Conference on Wood Modification, ed. H. Militz and C. Hill, Göttingen, Germany, 354-362.
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