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Better wood and a better wood composite – ecologically

Lunawood is the world’s leading producer of thermowood and recently added two new kilns to further boost capacity. Its Nordic Swan-labelled products make a great choice for numerous applications; their dimensional stability is ideal for cladding, decking, and other exterior use. The company has also recently launched Lunacomp, an advanced thermowood composite.

Lunawood primarily uses Finnish PEFC-certified wood and manages its logistics chain from forest to end-product to ensure a high and consistent level of quality. Radiata pine is used for knot-free exterior cladding and interior products, and denser and harder European ash for decking and flooring products.

Only high temperatures and steam are used in Lunawood’s process, which makes the end-product completely natural and chemical-free. water vapour is used as a protective gas and heat conductor to enable wood to be heated beyond its auto-ignition temperature, to 185-212 °C.

The treatment enhances properties such as dimensional stability, thermal insulation capability, resistance to decay, and reshaping properties. By carefully adjusting the temperature and duration of the process, just those properties required in the end-product can focused on.

During the first phase, the wood is heated to an intermediate temperature to dry it. During the second phase, when thermal modification takes place, its moisture content is reduced virtually to zero. During the third and final phase, the wood is cooled and moisturised to the desired level.

Lunawood currently produces two classes of thermowood: Lunathermo-S, which offers optimum stability, and Lunathermo-D, which offers optimum durability. Processed at around 185 °C, Lunathermo-S is primarily intended for indoor use, but can also be used in protected outdoor areas. Processed at around 212 °C, which is reflected in its darker colour, Lunathermo-D offers greater resistance to decay and even better dimensional stability, which means that it can be used both indoors and outdoors.

Stable and durable

Unlike untreated wood, which tends to crack and decay as it reacts to changes in the moisture content of the surrounding air, Lunawood’s thermowood maintains its size and shape and resists mould and decay across a very wide range of conditions.

Lunawood Thermo-D pine, for example, reacts 40% less to changes in the moisture content of the surrounding air, width-wise, than corresponding chemically treated wood. This makes it easy to use the Lunawood Profix fastening system in even the toughest conditions, for example.

Moisture content is roughly half that of untreated wood, and UV radiation causes less cracking than in untreated wood. As UV radiation causes the original colour of the wood to fade, however, Lunawood timber should be treated with a UV protection agent, such as oil, wax, or paint. As the wood’s natural resin has been removed, finishes only need to be reapplied very infrequently.

No chemicals are used in the Lunawood process, heat and steam are all that are needed. As a completely natural product, its thermowood can easily be recycled or reused. Photo: © Tekes, Matias Uusikylä

A new generation of wood composite

Lunawood recently set up a new subsidiary to take all the benefits of its thermowood and combine them with recycled plastic waste to create a new type of composite.

The product in question is Lunacomp, an innovative decking product for locations that call for a material capable of dealing with heavy wear and tear.

Excellent dimensional stability

Lunacomp – produced in a dedicated plant that was opened in early 2011 – is the outcome of around three years of R&D work aimed at improving the properties of wood composite products. This focused on developing a composite that was not only highly resistant to moisture but was also unconditionally stable and did not expand or contract with rises and drops in temperature, as many composites tend to do.

A 3-metre run of Lunacomp decking, for example, will expand or contract in length by only 3 mm at temperatures between 0 °C and 50 °C. Swelling as a result of variations in relative humidity is also very low.

Very tough too

Surface hardness was also a priority, to ensure that the product was truly hard-wearing. The company’s researchers scored a major success here, as Lunacomp is a very hard material – not only much harder than softwood and hardwoods such as ash and oak, but also significantly harder than other wood-polymer composites.

It also offers very good bending strength, thanks to its relatively high level of wood content. The latter gives Lunacomp an attractive, wood-like feel and texture as well.

The surface of Lunacomp decking features two different textures, one of which is specially designed for its anti-slip properties. Assembling a deck with Lunacomp is very easy, using t-clips to nail the decking to the substructure and connectors to join sections to each other for straight runs or corners. End pieces and side rails guarantee an attractive end-result. To ensure colour fastness, a UV protection compound is added to the ‘mix’ during production.

The result is a long-lasting and highly durable material. Containing no PVC, lunacomp is 100% recyclable, just like the raw materials it is produced from, only adding to its attractiveness.

The outcome of extensive R&D work, Lunacomp take all the benefits of thermowood and combines them with recycled plastic waste to create a new-generation wood composite with a winning range of properties. Photos: Peter Herring
> Martti Kauhanen & Henry Mantsinen
(Published in HighTech Finland 2011)