ABSTRACT
Abstract Penetration of adhesives plays an important role in wood adhesion, since wood is a porous material. Objectives of this work were (i) the evaluation of the influence of the degree of condensation of urea-formaldehyde (UF) resins on their penetration into beech, showing the distribution of the adhesive in the cell layers close to the bondline using microscopic detection, and (ii) the comparison of data for beech with results for fir obtained earlier. The degree of penetration mostly depends on the permeability and porosity of the wood surface as well as on the resin type and the size of the resin molecules. The process parameters, which also can affect penetration, were kept constant throughout all tests performed.
