Combined mixtures of polymeric diphenylmethane diisocyanates (pMDI) with Urea-formaldehyde-resins (UF) adhesives for wood panels are shown (a) by X-ray diffraction analysis (XRD) of the cured adhesive to present a certain percentage of microcrystallinity, this being due exclusively to the proportion of urea-formaldehyde resin present in the mix and, (b) by polarized light optical microscopy (PLOM) to present colloidal structures in which oligomers and colloidal structures of one resin have migrated within the colloidal structures of the other resin. (c) 2007 Wiley Periodicals, Inc.