Aqueous polyurethane dispersion with non-yellowing and good bonding strength for water borne polyurethane footwear adhesives applications

Abstract

With the evolution of legislation towards environmental friendly and low VOC products, the big multi-national footwear producers like Nike, Reebok and Adidas have already embarked on the campaign to demand their suppliers to supply water borne footwear adhesives. In this research, aqueous polyurethane dispersions (PUD) for footwear adhesives were prepared by polyaddition reaction using diol, isophorone diisocyanate, dimethylol propionic acid (DMPA) and 1,6-hexanediamine. Various formulations were designed to study the effect of the NCO/OH mole ratio, DMPA content, neutralization degree and chain extension on the performance of PUD. The weight-average molecular weight (Mw) and adhesive bonding strength were significantly affected by the DMPA content and degree of chain extension. The Mw was found to be increased when the NCO/OH ratio increased. As the particle size decreased, the amount of chain extender needed to optimize the chain extension was decreased. The non-yellowing property was achieved by using aliphatic isocyanate (IPDI).