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BIONÆR-Bionæringsprogram

WW-Net2 - High-frequency impregnation of wood

Awarded: NOK 1.2 mill.

The aim of the project HI-FRETECH was to develop a new impregnation process based on high-frequency (HF) electromagnetic waves to increase solution uptake and penetration depth in refractory wood species. Despite the application of various frequencies and treatment intensities in two different treatment plants, a reproducible increase in impregnability due to HF-treatment was not found. However, the experiments on HF-treatment indicated that heating of impregnation solutions result in increased solution u ptake. Further investigations revealed that heating to 55°C does not affect the chemical stability or the biocidal effectiveness of the wood preservative (Wolmanit CX-8). Results from impregnation trials in laboratory scale were verified in an extensive i ndustrial impregnation trial on cladding and terrace decking made of spruce. Cladding boards impregnated with the wood preserverative Wolmanit CX-8 at 55°C showed a significant higher solution uptake than those impregnated at 13°C. The boards retained 11 kg/m3 of Wolmanit CX-8 in the outermost 3 mm and thus complied with the requirements to cladding classified as NTR GRAN given by the Nordic Wood Preservation Council (NTR). The fulfillment of the NTR-classification is crucial for the commercialization of the product in Scandinavia. Treteknisk in Norway established a comprehensive field test of cladding and terrace decking in 2014 to investigate the performance of the new spruce products as compared to a number of commercialized wood materials. The test wi ll last 15 years.

Some wood species, known as refractive or hard-to-treat wood species, are difficult or impossible to impregnate in conventional pressure processes. Typical examples are Norway spruce (Picea abies) and eucalyptus (Eucalyptus globulus) that are classified a s difficult to treat (Class 3 according to EN 350-2) and very difficult to treat (Class 3-4), respectively. These two are the wood species of interest in HI-FRETECH due to their economic importance. While Norway spruce has many applications in the buildin g industry in entire Europe, eucalyptus is very important in Spain. Eucalyptus will be used as reference material for hardwoods in HIFRETECH. The Danish consortium partner, DWT, intends to transfer its expertise in HF-technology to wood impregnation proc esses. Initial tests have indicated that the implementation of HF-technology in impregnation processes can significantly increase the penetration depth and solution uptake in refractive wood species. The increased impregnability with wood preservatives, fire retardants, and wood modification agents will improve the properties and service life performance of cladding, panelling, decking, fire safety doors, outdoor furniture, garden infrastructure (sheds, fences, compost bins, post, etc), and structural el ements. This will increase the competitiveness of the forest-based value chain by strategic technology renewal of production systems. Moreover, end-of-life of wood based products will be optimised by achieving a better impregnation with wood preservatives , fire retardants, and wood modification agents under consideration of their total life cycle. The transfer of new knowledge will be achieved by close networking between research and industry in Germany, Norway, Spain, and Denmark.

Funding scheme:

BIONÆR-Bionæringsprogram