Dynamic wettability of different machined wood surfaces

Wetting dynamics on machined wood surfaces is of great interest for the adh esive bonding technology of wood. In this work, the change of apparent cont act angles with time of phenolresorcinol-formaldehyde (PRF), polyvinyl-acet ate (PVAc), and a series of probe liquids on sawed, planed, sanded, and raz or-blade-cut wood surfaces of Southern pine was studied by the sessile drop method using a CCD camera technique. The results indicate that the fastest wetting of the probe liquids occurs on the sanded surfaces because of high er surface roughness and the resulting increase in capillary forces as comp ared with the sawed, planed and razor blade cut surfaces. The fastest wetti ng of the PRF and PVAc resins occurred on the comparably smooth planed and razor-blade-cut wood surfaces. A smoother wood surface seems to provide bet ter wetting and penetration properties for high-viscosity liquids such as a dhesives, which probably can be attributed to less entrapment of air betwee n the resin and the wood structure.