INFLUENCE OF THE WETTING PROPERTIES OF POLYMERIC ADHESIVES ON THE MECHANICAL-BEHAVIOR OF CORK AGGLOMERATES

A series of adhesives, polyurethane prepolymers with alkane chains of different functionalities, were used in the production of cork agglome rates. The polymeric structure varied from long, linear chains in adhe sive M1 (14% isocyanate groups) to short, branched chains in adhesive M4 (30% isocyanate groups). The wetting properties of the adhesives we re studied through surface tension and contact angle measurements of t he polymeric liquids deposited on cork substrates. The mechanical beha viour of the cork agglomerates was studied through compression and thr ee-point bending tests, and the agglomerate structure was analysed by scanning electron microscopy (SEM). The relationship between the struc tural and wetting characteristics of the adhesives and the mechanical properties of the agglomerates was investigated. The experimental resu lts indicate that it is the work of adhesion for the adhesive/cork sys tem, and not only the contact angle, which determines the mechanical r esistance of the cork agglomerate.