Treatment of wood with formaldehyde. Acid catalysis of the reaction between formaldehyde and wood

IRG/WP 3146

T Vihavainen, K Piispanen, P Mansikkamäki

Formaldehyde reacts with the free OH-groups in wood forming cross-linking bonds. The reaction can be brought about without any catalyst but in that case the activation energy is very high and high temperatures and long reaction times are needed. Normally, the reaction is catalysed by different acids. Acid catalysts, however, tend to degrade the cellulose and the wood matrix causing reduction in the strength of the wood. The effect of the specific properties of catalysts on the cross-linking and hydrolytic reactions as well as the reaction kinetics have been inadequately investigated. Investigations on the treatment of wood with formaldehyde were started in 1976 at the Forest Products Laboratory of the Technical Research Centre of Finland. In the beginning, HCl-catalysed treatments were used which proved to reduce the strength properties of wood rather strongly. In continued trials more satisfactory catalysts have been sought in order to achieve maximal formaldehyde cross-linking and minimal degradation of the wood. The tests have included various inorganic and organic acids and metal halides soluble in water as well as sulphur dioxide (SO2) and boron trifluoride (BF3) in vapour phase. Some of the results are reviewed in this paper.


Keywords: ACID CATALYSIS; DIMENSIONAL STABILIZATION; FORMALDEHYDE; FUNGI; PINUS SYLVESTRIS; SULPHUR DIOXIDE; STRENGTH TESTS; WEIGHT LOSS

Conference: 80-05-05/09 Raleigh, North Carolina, USA


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