Anionomeric Waterborne Poly(urethane semicarbazide) Dispersions and Their Adhesive Properties

Aqueous polyurethane dispersions were prepared from isocyanate-terminated ionic polyurethane prepolymers by chain extension with dihydrazides. These water-borne dispersions had excellent adhesive properties and were used to bond leather and canvas. The base polymers were varied with respect to (1) the ionic content with the same chain extender and (2) the nature of the chain extender with the ionic content kept constant. Studies on the particle size and viscosity revealed that the ionic content had an influence on the aforementioned properties: the particle size decreased and the viscosity increased with increasing ionic content. The polarity of the films cast from the dispersions were determined with contact-angle measurements: hydrophilic character was exhibited by all the compositions. X-ray studies revealed that the increase in the ionic content led to increasing intensities of the diffraction peaks due to increased secondary forces of bonding. The tensile strength measurements showed that the films were highly elastomeric and had good mechanical strength, which varied with the composition. A shear strength and peel strength analysis of specimens obtained through the bonding of leather to leather, leather to canvas, and canvas to canvas revealed that the waterborne dispersions were excellent adhesives for bonding leather surfaces. Thus, a very efficient, ecofriendly waterborne dispersion of polyurethane that could find applications in bonding leather in the footwear industry was prepared successfully. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2833-2840, 2008