Restriction of liquid water spreading in overlaid plywood top veneer
2018
Cirule, D., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Kuka, E., Latvian State Inst. of Wood Chemistry, Riga (Latvia);Riga Technical Univ. (Latvia) | Verovkins, A., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Andersone, I., Latvian State Inst. of Wood Chemistry, Riga (Latvia)
Plywood overlaid with resin impregnated paper films is used in various decorative applications for which high stability of aesthetic qualities is of great importance. The top veneer of the plywood for these materials is perfectly protected from a direct contact with water as far as the covering film is not damaged. However, in case of film damage water can cause clearly visible defects in a relatively short period of time. To reduce these types of defects, unsophisticated and efficient way was developed. It involves filling the vessel system of the top veneer with industrial phenol-formaldehyde resin by using a hot-press. Influence of some phenol-formaldehyde resin properties on its penetration in birch veneer as well as the effect of wood moisture content were tested. The proposed top veneer pre-treatment method with phenol-formaldehyde resin reduced the average swelling zone distance from damage site by half for oven pre-dried plywood with 3% moisture content before treatment. Moreover, it was found that using plywood with moisture content of 9% the swelling zone distance was reduced by two thirds compared to untreated overlaid plywood.
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