Water absorption and contact angle measurement of native European, North American and tropical wood species to predict gluing properties

In order to optimize the gluing performance of wood splints with KPVAC-glues, it is of utmost importance to know the amount of water able to penetrate into the gluable wood splints. Therefore, in this study two techniques to measure the water absorption ability of building materials were applied on a variety of 40 representative tropical and native European wood species. The first method is a common German standard and measures the water absorption coefficient w(t). The second is based on the determination of the wettability of surfaces by measuring equilibrium contact angles of liquid water. Using a similar technique, we have concentrated our research on the dynamics (non-equilibrium) of a water drop contact angle. Differences among species are outlined and discussed primarily with respect to wood extractives contents and wood densities. Even though it must be assumed that both techniques are based on equal mathematical relations, a poor correlation was obtained.