Quality assessment of glued ash wood for construction engineering
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Delamination resistance and tensile shear strength (TSS) are essential for load-bearing timber structures. Thus these two factors were investigated on industrially bonded ash wood (Fraxinus excelsior L.) to check for the suitability of adhesively bonded ash wood as a building material. Two melamine urea formaldehyde (MUF) resins, two polyurethanes (PUR), one emulsion polymer isocyanate and one phenol resorcinol formaldehyde resin were taken for bonding. Face milled and planed surface series were made to highlight potential differences. For PUR, an additional series with dimethylformamide primed surfaces was also made. The influence of the mixing ratio and the closed assembly time were analysed for one MUF system. The samples for the TSS were tested in dry and wet conditions. 80 % of the tested series met the standard requirements (EN 15425; EN 301) in dry condition, whereas only 30% passed in wet condition. None of the adhesives tested were able to pass the delamination test. No distinct influence of the different parameters studied is notable for most of the adhesive systems, only extended CATs and lower MRs seem to improve the bond quality of MUF. In addition, chemical analyses were performed to find evidence for the poor bonding performance. It was found that acidic extractives, fatty acid content and pH of ash fell within the range of beech and spruce wood, with only formic acid being an exception with an amount four times higher than the other two wood species.
KeywordsWood Surface Adhesive System Polyurea Face Mill Beech Wood
This research was carried out at ETH Zurich and funded through the National Research Programme NRP 66 of the Swiss National Science Foundation and the forest and timber research fund of the Swiss Federal Office for the Environment FOEN.
- Brändli U-B (2010) Swiss National Forest Inventory. Results of the third survey 2004–2006. Editor, Birmensdorf, Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft WSL. Bern, Bundesamt für Umwelt, BAFU. ISBN 9783905621471Google Scholar
- DIN 53804-1 (2002) Statistical evaluation—Part 1: continuous characteristics. DIN Deutsches Institut für Normung e. V, BerlinGoogle Scholar
- DIN 55957 (2000) Binders for paints and varnishes: methylation and silylation of fatty acids and analysis by gas chromatography. DIN Deutsches Institut für Normung e. V, BerlinGoogle Scholar
- EN 15425 (2008) Adhesives—One component polyurethane for load bearing timber structures—Classification and performance requirements. European Committee for Standardization (CEN), BrusselsGoogle Scholar
- EN 301 (2013a) Adhesives, phenolic and aminoplastic, for load-bearing timber structures: classification and performance requirements. European Committee for Standardization (CEN), BrusselsGoogle Scholar
- EN 302-1 (2013b) Adhesives for load-bearing timber structures—Test methods—Part 1: determination of longitudinal tensile shear strength. European Committee for Standardization (CEN), BrusselsGoogle Scholar
- EN 302-2 (2013c) Adhesives for load-bearing timber structures—Test methods—Part 2: Determination of resistance to delamination. European Committee for Standardization (CEN), BrusselsGoogle Scholar
- Krackler V, Keunecke D, Hurst A, Niemz P (2011) Possible fields of hardwood application. Wood Res 56(1):125–136Google Scholar
- Mansouri NE, Yuan Q, Huang F (2011) Characterization of alkaline lignins for use in phenol-formaldehyde and epoxy resins. BioResources 6(3):2647–2662Google Scholar
- Ucar M, Ucar G (2008) Variations of wood acidity in hard-and softwoods during storage up to one year. Wood Research 53(4):105–114Google Scholar
- Vick C, Richter K, River B, Fried A (1995) Hydroxymethylated resorcinol coupling agent for enhanced durability of bisphenol-A epoxy bonds to sitka spruce. Wood Fiber Sci 27(1):2–12Google Scholar