The addition of small percentages of Na(+)-montmorillonite (NaMMT) nanoclay does not appear to improve much the performance of thermosetting phenol-formaldehyde (PF) and phenol-urea-formaldehyde (PUF) resins used as adhesives for plywood and for wood particleboard. X-ray diffraction (XRD) studies indicated that NaMMT does not become completely exfoliated when mixed in small proportions to PF resins, contrary to that observed for acid-setting urea-formaldehyde (UF) resins. Differential scanning calorimetry (DSC) indicated that NaMMT has no accelerating effect on the curing of alkaline PF resins, contrary to that observed for UF resins. (C) Koninklijke Brill NV, Leiden, 2010