Highly effective impregnation and modification of spruce wood with epoxy-functional siloxane using supercritical carbon dioxide solvent
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Chemical modification of wood is an established approach to improve its biological durability, water repellence, dimensional stability, and UV resistance. Norway spruce wood (Picea abies) in dry state, however, has an extraordinarily high recalcitrance towards impregnation with liquid modification reagents as drying triggers the irreversible closure of pits, i.e. the cell-to-cell valves in softwood. In the present study, it is shown that supercritical carbon dioxide is a highly suitable impregnation medium to overcome the recalcitrance of dry spruce wood. This has been exemplarily demonstrated for deca(dimethylsiloxane)-α,ω-diglycidylether (D8M 2 OG ), a linear oligosiloxane with terminal epoxy-functionalities, which could be loaded into respective wood samples affording a weight gain of up to 63%. The thermally assisted reaction of the epoxy-functional siloxane with the wood polymers was catalysed with ring-opening Tin (II) octoate. The effort resulted in a remarkably reduced wettability with water, as evident from contact angle measurements (~ 140°), and in a significant decrease (≤ 20%) of the sample’s sensitivity towards moisture-induced dimensional changes.
The authors gratefully thank Prof. Dr. Martin Wendland from the Institute for Chemical and Energy Engineering of BOKU University Vienna, Austria, who enabled the use of the scCO2 plant and Markus Hauptmann who operated the scCO2 plant.
Compliance with Ethical Standards
Conflict of interest
The authors declare no conflict of interest.
- Deerberg G, Danzig J, Jelen E (2006) Modifizierung von einheimischen Hölzern durch Imprägnierung mit überkritischem Kohlendioxid (Modification of local wood species using supercritical carbon dioxide). Frauenhofer-Institut für Umwelt-, Sicherheits- und Energietechnik Oberhausen UMSICHT, OberhausenGoogle Scholar
- Demessie ES, Hassan A, Levien KL, Kumar S, Morrell JJ (1995) Supercritical carbon dioxide treatment: effect on permeability of Douglas-fir heartwood. Wood Fiber Sci 27:296–300Google Scholar
- DIN EN 84:1997-05 Wood preservatives—accelerated ageing of treated wood prior to biological testing—Leaching procedure (1997)Google Scholar
- Esteves BM, Pereira HM (2009) Wood modification by heat treatment: a review. BioResources 4:370–404Google Scholar
- Ghosh SC, Militz H, Mai C (2009) Natural weathering of Scots pine (Pinus sylvestris L.) boards modified with functionalised commercial silicone emulsions. BioResources 4:659–673Google Scholar
- Jelen E, Ghosh SC (2009) Modification of domestic timbers by impregnation using supercritical carbon dioxide-a comparison. In: European conference on wood modification, StockholmGoogle Scholar
- Lehringer C, Richter K, Schwarze FW, Militz H (2009) A review on promising approaches for liquid permeability improvement in softwoods. Wood Fibre Sci 41:373–385Google Scholar
- Rowell RM (2005) 14 Chemical Modification of Wood. In: Handbook of wood chemistry and wood composites, vol 381Google Scholar
- Saka S, Miyafuji H, Tanno F, Yamamoto A, Tanaka M, Yamamoto K (1997) Modification of wood. US Patent US5652026,Google Scholar
- Siau J (1995) Wood: influence of moisture on physical properties. Virginia Polytechnic Institute and State University. Blacksburg. 227 pgs. ISBN 0-9622181-0-3Google Scholar