The cohesion of cork agglomerates is determined by the strength of the adhesive joint established between the polymeric adhesive and the cork particles. The ability of adhesives to form good joints depends, among other factors, on the wetting of cork by the adhesives. The main objective of this research was to study the behaviour of adhesive drops deposited on cork substrates through measurements of contact angles and their time dependence. Several polyurethane prepolymers were tested to establish a correlation between the wetting characteristics and the chemical structure and physical properties of the adhesives. The effect of the morphology of cork on the interfacial properties was also investigated. The initial contact angles were related to the chemical nature of the adhesive. The kinetics of the wetting process were found to depend mainly on the viscosity of the adhesive.

Cellular polymers constitute an important field of investigation due to their unique properties as shock absorbers and thermal or acoustic insulators. The knowledge of the wetting properties of these materials is important in applications where adhesion or weathering behavior are an issue. In this study, cellular polyurethane polymers were used to investigate the effect of the cellular structure on the wetting properties. The polymeric substrates were analyzed by scanning electron microscopy and the wetting properties were studied by goniometry. The contact angles of water and diiodomethane were measured as a function of time and the surface tension of the expanded polymers was evaluated by the geometric and harmonic mean methods. It was found that the wettability and the surface energy of the cellular polymers increase as the density decreases. © 1997 John Wiley & Sons, Inc.

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