Water-resistant plywood adhesives prepared from phenolated larch bark in the presence of various combination catalysts

The properties of larch barks phenolated with various combinations of acidic catalysts and the properties of adhesives synthesized with these phenolated barks have been investigated. The results have indicated that the catalyst species used has great effects on bark phenolation and many properties of the resultant bark adhesives (BA). High-performance liquid chromatography (HPLC) and Gel permeation chromatography (GPC) analyses have indicated that the amount of phenol bound to the bark and recondensation of phenolated components decreased with decreasing acidity of the combination catalysts used, resulting in decreases in the extent of phenolation, bound phenol content, and molecular weight but an increase in the number of active sites on the phenolated bark. Larch bark phenolated with combined catalysts can be used to prepare water-resistant wood adhesives with low formaldehyde emission. By judiciously decreasing the acidity of the catalyst used for bark phenolation, the properties of BA, such as storage life, bond strength, and formaldehyde emission, could be effectively improved. BA-C showed the acceptable wet bond strength and a sufficiently low formaldehyde emission, making it a good potential candidate for commercial applications. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012