Acetylated Wood

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Windsor, United Kingdom
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Acetylated Wood



Accoya® is the world’s leading high technology long life wood. The Accoya® wood production process takes sustainably-sourced, fast growing softwood and enhances nature, creating a modified wood that matches or exceeds the durability, stability and beauty of the very best tropical hardwoods.
Accoya – ideal for windows, doors, cladding, decking, structural and much more
For window frames, Accoya® wood is the material of choice. Not only does it have extremely low thermal conductivity but it matches or exceeds the durability and dimensionally stability of the best tropical hardwoods. It can be opaque coated or, for those wishing to enjoy the natural look of wood, translucent coated. Accoya®’s low maintenance requirements add to its cost effectiveness and environmental credentials.
Exterior doors and shutters should be durable, dimensionally stable (to prevent doors jamming and becoming difficult to open and close in bad weather) and easy to maintain. Accoya® wood meets these criteria and may be used to create simple or complex designs with a choice of coating finishes with typically greatly improved lifetimes.
Accoya® wood is a perfect solution for exterior cladding, siding and façades where aesthetics, less frequent maintenance, dimensional stability, durability and insulation value are key factors. Accoya®’s versatility makes it ideal for use in residential, commercial and industrial structures.

Further info from manufacturer on ACCOYA® WOOD
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Accoya® Wood - Benefits
Accoya wood’s durability makes it very long lasting, at least:
- 50 years above ground
- 25 years in-ground or freshwater contact
Accoya wood forms an effective barrier to mould and insect attack; it is indigestible to microorganisms and insects and therefore more durable to wood-destroying fungi and virtually rot-proof.
Accoya wood offers outstanding dimensional stability in both radial and tangential directions (thickness and width) meaning that it has minimal swell and shrinkage and may be confidently used in applications where it will encounter varying moisture conditions – even in freshwater immersion.
Tests have shown a reduction in swelling caused by moisture uptake of 75% or more. From oven dry to water saturated conditions, the swelling and shrinkage of acetylated wood is only minimal and, in fact, better than tropical hardwoods.
By significantly enhancing the durability and dimensional stability of fast-growing and abundantly available certified wood species, Accoya wood provides compelling environmental advantages over slow-growing hardwoods, woods treated with toxic chemicals and non-renewable carbon intensive materials such as plastics, metals and concrete. Accoya wood is fully reusable and recyclable. Reuse is recommended but Accoya may be safely incinerated for bio-energy.
Accoya® wood’s superior coatings performance is primarily due to its outstanding dimensional and UV stability. This effectively means that major coating systems can be used on Accoya® with significantly improved performance.
Accoya wood has superior resistance to UV degradation, with extensive tests demonstrating that the natural beauty of the wood lasts longer in even the severest exposed conditions. UV resistance of wood improves the life of any coating by providing a sound coating substrate. It also allows a wider range of feasible colour options. For example, very light pastel coloured stains and clear coatings can be safely used because Accoya will not darken quickly and ruin the effect as most other woods do.
Each batch is analysed and Accoya wood always meets the requirements of Durability Class 1 for Use Classes 1-4 in accordance with EN 350-1 & EN 335-1. Because Accoya wood is modified all the way through, rather than just at the surface, when it is cut, planed or jointed there are no exposed unprotected surfaces in any dimension. This completely removes the need to apply additional chemical preservatives as is necessary with unmodified or envelope treated woods. Accoya wood is easy to machine and process manually, creating no challenges for product manufacturers and end users. Accoya wood can be fixed in the same way as other commonly used softwood species. As with most durable woods, Accoya contains a small amount of acid. It is therefore strongly recommended that corrosion resistant fixings, such as high quality stainless steel, are used.
Accoya wood inspired OAK architects to design two wooden heavy traffic road bridges for the city of Sneek in the Netherlands. Accoya was finger jointed and laminated into large sections measuring 1.08 x 1.4 metres to create these innovative structures, the first of their kind in the world. Accoya wood is a brilliant material for windows and doors as it offers improved thermal insulation in comparison with commonly used wood species and is more durable and dimensionally stable than the best tropical hardwoods. Coatings last longer and it is perfect for transparent, translucent or opaque coatings … whatever captures your imagination. Accoya wood is suitable for cladding, siding and façades where aesthetics, stability, durability and less frequent maintenance are considerations. Here it is used to clad a contemporary extension using an inclined open boarding system, finished with an environmentally friendly dark stain. This is only possible using a wood as stable and UV resistant as Accoya. In specifying decking, jetties and pontoons, beauty, strength and all-weather performance are important. A dimensionally stable material that will stay flat and has very minimal bow, cup, warp and split and will not be affected by fungi or rot is desirable. It is also important that the wood is non-toxic and therefore safe for people and animals. Accoya wood meets these requirements. Accoya wood is an excellent choice for shutters, louvres and solar shading. At Scottish Widows’ Exchange Place development, eye-catching bespoke solar shading and ventilation louvres were incorporated to prevent excessive heat gain. The system included 1,060 Accoya wood fins. The solar shading has a life expectancy of 60 years and the finish applied carries a 10 year warranty.
Accoya® Wood - Creating the World’s Leading Acetylated Wood
Accoya is based upon acetylated wood technology, a process that has been studied by scientists around the world for more than 75 years. This method of improving wood has been proven to deliver such superior performance that it has long been used as the “gold standard” against which other methods are measured.
The physical properties of any material are determined by its chemical structure. Wood contains an abundance of chemical groups called “free hydroxyls”. Free hydroxyl groups adsorb and release water according to changes in the climatic conditions to which the wood is exposed. This is the main reason why wood swells and shrinks. It is also believed that the digestion of wood by enzymes initiates at the free hydroxyl sites – which is one of the principal reasons why wood is prone to decay.
Acetylation effectively changes the free hydroxyls within the wood into acetyl groups. This is done by reacting the wood with acetic anhydride, which comes from acetic acid (known as vinegar when in its dilute form). When the free hydroxyl group is transformed to an acetyl group, the ability of the wood to absorb water is greatly reduced, rendering the wood more dimensionally stable and, because it is no longer digestible, extremely durable.
The Process
The use of sustainably forested timber, the attachment of a molecule which naturally occurs in all wood and the recycling of the by-products, make the Accoya® wood production process highly efficient and environmentally positive.
Windows and doors
Cladding, Siding & Facades
Shutters & Louvres
Decking & Marinas
Bridges & Other Structural
Coatings for Accoya®
Accoya® may be coated in the same way as any other wood, using transparent, translucent or opaque coatings. Impregnating oils and other finishes may also be used. Accoya®’s exceptional qualities including it’s dimensional stability, that reduces swelling stress on coatings, and UV resistance mean improved coatings life and less maintenance. Multiple trails in many types of environments have shown 3-4 times greater coatings life with many types of coatings. Trials are underway with several leading coating manufacturers to develop guarantees for their systems used in conjunction with Accoya®.
In many applications the frequency and cost of maintenance is a critical factor in determining the choice of material that is used. For designers, architects, builders and property owners extended coatings life reinforces the excellent natural performance attributes of wood – beauty, strength, thermal efficiency and machinability – and reiterate the enhanced performance attributes of Accoya®: durability, dimensional stability and reliability.
Accoya® Wood - Enabling Nature
Accoya® wood is the result of more than 75 years’ research and development that have brought together a long-established and extensively researched wood modification technique, acetylation, and leading-edge technology to create and make this extraordinary “new wood” commercially available for the first time.
Accoya® is set to become the material of choice for exterior applications and can be used for virtually anything, from windows to doors, decking to cladding and even for applications which are presently the preserve of non-sustainable materials.
Accoya® is perfect for outdoor use, with the performance of the best tropical hardwoods and much more besides:
- Class 1 durability – the best available
- Outstanding dimensional stability which dramatically improves coatings adhesion and product performance
- Lasting for 50 years above ground and 25 years in-ground
- Environmental compatibility – non-toxic, 100% recyclable and sourced from sustainable forests
- Consistent, measurable quality all the way through the wood, not just at the surface
- Retained natural strength and beauty, increased hardness
- Consistent supply from sustainably managed forests and plantations
Accoya® Wood - Tried & Tested
Extensive laboratory and field testing by leading institutes around the world (including in New Zealand, USA, UK, Sweden, Malaysia, Indonesia, Russia, the Netherlands and Japan) has shown the performance of acetylated wood to be extremely reliable.
Accoya® wood has been thoroughly tested for dimensional stability, durability, UV resistance, paint retention and in-ground conditions to ensure optimal performance. Indeed, it is so reliable that for many years it has been – and continues to be – used by scientists as the benchmark against which other treatments and modifications are measured.

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