This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the dimensional stability
of birch wood. Therefore, three different low molecular weight PF resins were synthesized in 1L laboratory
reactor with average molecular weights (Mw) of 292, 528, and 884 g/mol. Solid content, pH, viscosity,
density and free formaldehyde content of prepared PF resins were determined. Silver birch (Betula pendula
spp.) wood blocks and veneers were vacuum impregnated with 10% (w/w) of PF resin water solutions. The
weight percent gain (WPG) and bulking after drying and curing of resin treated wood specimens were
determined. The leaching procedure according to EN 84 was performed to evaluate the PF resin fixation
stability. The anti-swelling efficiency (ASE) of treated specimens during seven soaking-drying cycles was
examined. The dimensional stability of birch wood after treatment with all tested PF resins was significantly
improved. The ASE of birch wood blocks treated with PF resins after the 1st soaking-drying cycle was in
the range of 42–54% depending on the resin used. The ASE was affected negligibly during testing and after
the 7th soaking-drying cycle it was still in the range of 39–53%.
Keywords: Phenol-formaldehyde resin, dimensional stability, birch
Authors
Juris Grinins
Vladimirs Biziks
Janis Rizikovs
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