CURING BEHAVIOR OF WOOD ADHESIVES UNDER HIGH-PRESSURE STEAM .3. BONDING STRENGTH OF PHENOLIC RESIN

This paper deals with the bonding performance of phenol-formaldehyde ( PF) resin in steam-injection heating at 160 degrees C; the effects of additives and steam-injection time on bonding strength were studied. I n addition, suitable bonding condition for PF resin in steam-injection heating was investigated. The results are summarized as follows: as s team-injection time increased, the bonding strengths of 3-ply plywood, glued with a neat PF resin and wheat flour extended PF resin after cy clic boiling treatment decreased. The reason seemed that swelling, dil ution, and over-penetration of PF resin took place in long steam-injec tion heating. With sodium carbonate-added resin, the bonding strength increased gradually with increasing steam-injection time. To improve t he bonding strength in a short heating time, intermittent steam-inject ion heating was tried. When a neat resin and sodium carbonate-added re sin were used, the bonding strengths were improved dramatically. There fore, intermittent steam-injection heating was effective for the devel opment of the bonding strength of PF resin.