The studies presented in this paper focus on how the size of the batches treated and the size of the individual wood samples treated influence the process and resulting mass loss, EMC reduction, and reduction in impact bending strength of the wood. Treatments were made in superheated steam according to the Thermowood© process. Resulting properties after industrial treatment and laboratory treatment were compared.
Paired samples cut from Norway spruce and Scots Pine planks were heat treated in industrial Thermowood® kilns together with the regular production and in a laboratory autoclave equipped with X-ray CT-scanner. Paired test samples were made by cutting each test plank into cross-sections of length 10mm, 50mm, 100mm, and either 1.25 m or 1.6 m before treatment. Reference samples from each plank were used to determine properties of untreated material.
The studies showed a strong size effect where small samples showed both different reactions to the surrounding climate and different resulting material properties after treatment as compared to larger samples and full size planks. Laboratory treatment lead to greater mass loss than industrial treatment. The results show that the size influence is different for reduction of EMC, mass loss, and reduction of impact bending strength.
Keywords: thermal modification, size effect, EMC, mass loss, impact bending strength
Authors
Källander B.
Stora Enso Wood Products. Falun
Wood Science and Engineering, Luleå Technical University, Skellefteå, Sweden
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