Changes in content of furfurals and phenols in self-bonded laminated boards
2013 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 3, 4056-4071 p.Article in journal (Refereed) Published
Pressing beech veneers at high temperatures has been shown to be a reliable method for manufacturing laminated boards without adhesives. The reasons behind the self-bonding phenomenon as well as the causes of the waterproof character gained by the boards being pressed at 250 degrees C were investigated. Water leachates from the dried and the hot-pressed veneers were analysed by UV-spectroscopy, high-performance liquid chromatography (HPLC), and solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C NMR). Press-plate temperatures during hot pressing were 200, 225, and 250 degrees C. After pressing, an increased content of 5-(hydroxymethyl) furfural (not at 250 degrees C) and conjugated phenols was observed in the bonding lines (interfaces) compared to the inner part of veneers of the self-bonded boards. Furfural contents were low and relatively similar, but 5-(hydroxymethyl) furfural (HMF) showed an abrupt decrease in the bonding line when the temperature increased from 200 degrees C to 225 degrees C and especially to 250 degrees C. The contribution of caramelization to browning and bonding is suggested. In studies with CP/MAS 13C NMR, a higher content of phenolic units in beech lignin was observed during hot pressing at 225 degrees C. Homolytical cleavage of beta-O-4 structures in lignin as well as the condensation reactions involved are discussed
Place, publisher, year, edition, pages
2013. Vol. 8, no 3, 4056-4071 p.
Research subject Wood Physics
IdentifiersURN: urn:nbn:se:ltu:diva-11330Local ID: a45a745c-873d-4504-8949-5800a9272225OAI: oai:DiVA.org:ltu-11330DiVA: diva2:984280
Validerad; 2013; 20131003 (ysko)2016-09-292016-09-29Bibliographically approved