Small amounts of fluorinated polyethers, and in particular a nonionic fluorinated polyether, can upgrade considerably the cold-water swelling and internal bond strength of wood particleboard bonded with urea-formalclehyde (UF) resins. The effect is maximized at an additive concentration of about 0.1 wt % with respect to the adhesive resin solid content. The effect of the fluorinated polyether appears to be greater with older UF resins, which have a more pro-nounced colloidal state. The mechanism appears to be somewhat related to the reduction of the interfacial tension of the resins, with improved substrate wetting leading to better adhesion. The addition of a fluorinated polyether well in advance of resin use further enhances the improvement. (C) 2007 Wiley Periodicals, Inc.