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it view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia accoya a type of modified wood sample of acetylated wood accoya three laminated acetylated wood specimen acetylated wood or commercially known as accoya is a type of chemically modified wood that is produced through a chemical modification process 1 2 3 it is produced from a chemical reaction named as acetylation involving acetic anhydride and a modification process to make wood highly resistant to biological attacks by fungi and wood boring insects and durable to environmental conditions 4 5 it is a new wood product in the field of wood science following decades of research and experimentation it is increasingly known as accoya which is the brand name of the primary maker 6 the chemical modification occurs through the reaction of wood polymers especially the free hydroxyl groups present in lignin and hemicelluloses without the need of a catalyst forming bonds between them the substances used such as anhydrides modify the structural components of wood without leaving toxic residues this process prevents approximately 80 90 of hydroxyl oh groups from forming hydrogen bonds with water molecules effectively locking the cellular walls with the material the chemical reagents employed are non toxic and the potential of recycling and disposal of acetylated wood can be accomplished without any restrictions 7 acetylated wood is characterized by its very light colour and has been shown to possess high durability 8 and strong hydrophobic properties as various research studies have indicated 9 10 11 this wood is suitable for outdoor wooden structures 8 as well as exterior flooring and decks it is primarily produced from pine wood radiata pine although beech is also occasionally used with this technology acetylated wood has minimal moisture absorption significantly enhancing dimensional stability and natural resilience 12 development of the technology edit the first patent for wood acetylation was filed in 1930 by h suida an austrian chemist 13 further fundamental research was conducted in the united states at the forest products laboratory by the researchers alfred j stamm and harold tarkow during the 1940s 14 the primary material for acetylated wood is one that contains lignocellulose since wood acetylation aims to produce durable wood for outdoor use wood which typically contains lignin and cellulose is usually the material of choice acetylation is typically performed using acetic anhydride in specialized reactors made of stainless steel given that acetic anhydride decomposes to produce acetic acid when it comes into contact with water the moisture content of the raw material significantly influences the consumption of acetic anhydride therefore it is advantageous to use raw materials that are as dry as possible 2 4 in essence any type of wood can be acetylated however since each type of wood behaves slightly differently during acetylation the process needs to be adjusted to suit the specific wood type to achieve the desired product properties production process edit diagram showing the blocking of free hydroxyl groups after the acetylation reaction diagram of cellulose acetylation the red hydroxyl groups oh of cellulose see above are partially acetylated by acetic anhydride forming ester groups while the resulting acetic acid is decomposed the degree of acetylation varies for example two out of three hydroxyl groups are acetylated for each glucose structural unit the process begins with the introduction of chemical reactants into wood raw material and the injection of the acetic anhydride solution the solution can be introduced under vacuum excess pressure or at atmospheric pressure the acetylation process of wood involves impregnating the wood with an acetic anhydride solution under pressure or vacuum heating the solution and the wood and achieving a temperature of around 120 c to allow the actual acetylation reaction between the wood and the reagent the excess acetic anhydride solution that is not absorbed by the wood can be removed either before or after the acetylation reaction to extract unreacted acetic anhydride and the resulting acetic acid from the wood a final step involving distillation with water or steam is carried out to ensure that the wood is essentially free from acetic anhydride and acetic acid this step is mainly to prevent the release of acetic acid odors from the final product into the environment which is undesirable the solution resulting from dehydration vacuum extraction and post processing is collected and separated the entire production process is time consuming 12 degree of acetylation edit the degree of acetylation i e acetyl content needs to be estimated by various methods to achieve successful results a minimum acetylation degree of at least 20 22 is required for high strength wood due to the incorporation of acetyl groups similar to water molecules causing swelling of wood the increase in volume can serve as a parameter for the degree of acetylation on the other hand the percentage increase in weight known as wpg weight percent gain can be used after acetylation this also allows for conclusions to be drawn regarding the quantity of anhydrous oxalic acid that ultimately becomes chemically bound to the wood in the cell walls further parameters that can be used to assess the degree of acetylation include resistance to water leaching electrical conductivity or methods such as hplc analysis or spectrophotometry 12 timber bridge in the netherlands which was constructed with glulam of acetylated pine wood properties and characteristics edit acetylation permanently alters the chemical composition of wood this chemical modification positively affects various mechanical and physical properties as well as the wood s resistance to insects and microorganisms that degrade it depending on the type of wood and the extent of modification acetylation typically results in wood discoloration and an increase in density and hardness 15 depending on the level of post processing the final wood product may have a more or less pronounced acetic acid odor easily detectable during cutting water absorption edit during the acetylation process the hydrophilic hydroxyl groups within the polymer structure of the wood s cell walls chemically react to form highly hydrophobic acetoxy groups as a result the hydrophobic nature of wood significantly limits its ability to absorb or release water this means that acetylated wood exhibits a much lower equilibrium moisture content compared to natural non acetylated wood the maximum equilibrium moisture content of regular wood is typically around 30 referred to usually as fiber saturation point of wood while wood that has undergone acetylation treatment with a wpg of 20 has a final equilibrium moisture content of only 10 12 furthermore water absorption rate is greatly reduced during the acetylation process 16 dimensional stability edit replacing the hydrophilic hydroxyl groups within the polymer structure of wood s cell walls e g cellulose lignin hemicelluloses with hydrophobic acetyl groups also positively impacts its dimensional stability this refers to the wood s ability to maintain its dimensions in changing climatic conditions acetylated wood exhibits approximately 70 to 80 greater dimensional stability compared to untreated natural wood consequently it experiences significantly reduced swelling and shrinkage 16 biological resistance edit acetylation enhances the biological natural resistance of wood its resistance to decay by fungi insects and other factors is significantly improved the reduction of maximum equilibrium moisture content to the range of 10 20 in acetylated wood prevents the minimal moisture required for fungal growth additionally the molecular structures of the cell wall which are easily degraded by fungi change with acetylation in such a way that fungal hyphae can no longer penetrate through the porous cell wall and break it down resistance to weathering edit various wood species can be fully protected from brown white or soft rot through acetylation and upgraded to the highest resistance class class 1 such as exceptionally durable tropical species like teak merbau azobe and iroko acetylation can also improve wood s resistance to decay by bacteria and termites 16 resistance to environmental conditions edit acetylated wood specimens which have undergone a 10 year soil test in addition to wood decay caused by fungi wood exposed to sunlight and rain hail snow undergoes photochemical degradation and gradual decomposition on the wooden surface exposed to sunlight low molecular weight degradation products from photo oxidative reactions are slowly and gradually produced primarily triggered by ultraviolet radiation these degradation products are washed away by rain over time resulting in either wood bleaching and a change in surface structure or localized dark spots because acetylated wood has a much lower equilibrium moisture content than untreated wood the degradation products are washed away more slowly additionally the photooxidative degradation of acetylated wood s polymers occurs more slowly acetylation cannot stop the process of photochemical degradation in wood but it can significantly slow it down 16 recent research has shown that acetylated wood is best treated with surface finishes or even paints 17 industrial producers edit the first trials to scale up the process during the decades of 1960 and 1970 were fully unsuccessful however the wood scientist dr holger militz along with his research coworkers started up during the 90 s at shr in the netherlands the first feasible pilot plant with successful trials thus this led to the scaling up of the acetylation process afterwards the company named accsys technologies based in london formerly titan wood was the sole industry producing acetylated wood in 2007 the production of this product on a larger scale began using radiata pine pinus radiata sourced from australia and new zealand under the brand name accoya at the company s manufacturing facilities in arnhem in the netherlands 18 eastman chemical began producing acetylated wood again in 2024 at its kingsport location through a joint venture with accsys technologies after having taken a decade long break in production for unknown reasons from 2014 to 2024 5 19 types of modified wood edit furfurylated wood kebony which is also produced from radiata pine but can also come from american southern yellow pine and ash 20 thermally modified wood wood that has undergone thermal modification in a kiln without the use of chemicals impregnated wood which is wood that has been pressure treated with protective chemical compounds further reading edit roger m rowell acetylation of wood 2006 forest products journal 56 9 4 12 13 holger militz overview report acetylated wood scientific and technological foundations material economic possibilities and limits current status of implementation sgd south forestry research institute rhineland palatinate 2011 online on fawf wald rlp de retrieved on january 6 2014 pdf 915 kb ulf lohmann wood lexicon 4th edition nikol verlagsgesellschaft hamburg 2010 isbn 978 3 86820 086 7 callum a s hill wood modification chemical thermal and other processes wiley 2006 isbn 0 470 02172 1 fuchs w 1928 on the knowledge of genuine lignin i the acetylation of spruce wood berichte der deutschen chemischen gesellschaft 61 5 948 951 references edit hill callum a s 2006 01 13 wood modification chemical thermal and other processes wiley doi 10 1002 0470021748 isbn 978 0 470 02172 9 retrieved 2026 09 08 sandberg dick kutnar andreja mantanis george 2017 12 01 wood modification technologies a review iforest 10 6 895 908 doi 10 3832 ifor2380 010 retrieved 2023 11 08 chemical modification of wood by acetylation or furfurylation a review of the present scaled up technologies by george i mantanis bioresources 2017 03 01 retrieved 2026 09 08 design castus 2019 01 23 acetylated timber acetylated wood non toxic wood treatment accoya retrieved 2023 10 12 1 2 springer handbook of wood science and technology springer handbooks cham springer international publishing 2023 p 897 doi 10 1007 978 3 030 81315 4 isbn 978 3 030 81314 7 issn 2522 8692 acetylated wood accoya accsys plc 2025 07 03 retrieved 2026 09 08 holger militz übersichtsbericht acetyliertes holz naturwissenschaftliche und technologische grundlagen materialtechnische und ökonomische möglichkeiten und grenzen aktueller stand der umsetzung sgd süd forstliche versuchsanstalt rheinland pfalz 2011 accessed in august 2023 1 2 mantanis george i lykidis charalampos papadopoulos antonios n 2020 07 23 durability of accoya wood in ground stake testing after 10 years of exposure in greece polymers 12 8 mdpi ag 1638 doi 10 3390 polym12081638 issn 2073 4360 pmc 7465449 pmid 32717892 rowell roger m september 2006 acetylation of wood journey from analytical technique to commercial reality forest products journal 56 9 4 12 papadopoulos antonios n 2006 04 01 pyridine catalyst acetylation of pine wood influence of mature sapwood vs juvenile wood holz als roh und werkstoff 64 2 134 136 doi 10 1007 s00107 005 0056 x issn 1436 736x alfredsen g flæte p o militz h 18 november 2013 international wood products journal international wood products journal 4 3 137 143 doi 10 1179 2042645313y 0000000034 1 2 3 holger militz übersichtsbericht acetyliertes holz naturwissenschaftliche und technologische grundlagen materialtechnische und ökonomische möglichkeiten und grenzen aktueller stand der umsetzung sgd süd forstliche versuchsanstalt rheinland pfalz 2011 retrieved august 2020 1 2 rowell roger m september 2006 acetylation of wood pdf forest products 56 9 4 12 retrieved 25 december 2023 ibach rebecca e rowell roger m 2021 02 24 usda forest service forest products laboratory acetylation of wood 1945 1966 forests 12 3 mdpi ag 260 doi 10 3390 f12030260 issn 1999 4907 ulf lohmann holzlexikon 4th edition nikol verlagsgesellschaft hamburg 2010 isbn 978 3 86820 086 7 1 2 3 4 holger militz overview report acetylated wood scientific and technological foundations material technical and economic possibilities and limitations current implementation status sgd süd forstliche versuchsanstalt rheinland pfalz 2011 retrieved in august 2020 27929 psp accoya verwitterung en cerdia print pdf accoya 2019 accoya manufacturing process english in accoya com production underway at new accoya plant building products digest the merchant magazine a 526 media group publication 2024 09 04 retrieved 2024 11 12 kebony manufacturing process english in de kebony com 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