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The wood foam panel consists entirely of renewable raw materials.
© Manuela Lingnau / Fraunhofer WKI
Lightweight construction material
10.03.2014

Wood foam replaces artificial insulation material

Researchers from the Fraunhofer Institute for Wood Research WKI in Braunschweig have developed a process which allows foam to be produced from wood particles. It is as light as balsa wood, a material commonly used for model aircraft, and has excellent thermal insulation properties due to its pore structure. The material is suitable as insulation, packing material and for structural applications. The form-stable wood foam can currently be produced at a laboratory scale.

Wood foam could be a good alternative to crude oil-based foams such as polystyrene or polyurethane. “Our wood foam can be used exactly like classic plastic foams, but is a one hundred percent natural product made of renewable raw materials,” explains Professor Volker Thole, Head of the Technology for Wood-based Materials Department at Fraunhofer WKI.

Until now, wood-based insulation has had the disadvantage that it sheds fibres and is less form-stable than plastic insulation. “Insulating fleece made of wood fibres often subsides in the middle due to temperature fluctuations and moisture. That means that some of the insulating effect is lost,” adds Thole. The wood foam developed at Fraunhofer WKI is roughly as stable as classic plastic foams.

Testing structural properties

The foams are being tested based on the standards applicable for insulating materials. Criteria include the mechanical and thermal insulation properties, as well as reaction to moisture and fire. The results to date are highly promising: The thermal conductivity should be roughly equivalent to polystyrene and mineral fibre panels (thermal conductivity group: WLG-040). The fire properties are similar to other natural insulating materials such as wood-fibre or wood-wool fleece.

Domestic wood such as spruce or beech is the base material for the insulation. Wood from forest thinning and sawing by-products can be used. The scientists are experimenting with various types of wood to find out which are particularly suitable. To produce the foam, the researchers first grind the wood to fine particles until a slimy mass is formed. They foam this suspension with a gas. The foam then hardens, with the substances in the wood supporting the hardening process. An alternative production method is based on special chemical processes. “It’s like baking, when the dough rises and hardens in the oven,” explains the head of the project, Julia Scholtyssek. The result is a light base material, with a density of between 40 and 200 kilograms per cubic metre. It can be processed to form rigid foam panels or flexible foam mats.

Partners wanted for industrial implementation

As early as the 1950s, there were individual foamed insulating materials based on waste from the paper industry, in particular in Scandinavia. However, they were soon replaced by petrochemical plastics. The manufacturers’ expertise has largely been lost. Production of foams made entirely of wood is a new research area. As the environmental advantages of the material are promising from a marketing perspective, the researchers from Fraunhofer WKI hope to find an industrial partner for cooperation. They are optimistic that they will be able to develop their method for mass production within two years.

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