Aqueous polyurethane (APU) dispersions having a solid content of 50% were synthesized using dimethyol propionic acid (DMPA) as the stabilizing moiety. The principal diols used were poly-1,4-butylene adipate glycol (PBA). The diisocyanates used in this study were a 30:70 blend of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). All these samples were neutralized using triethylamine (TEA) and chain-extended using ethylene diamine (FDA). The effects of the COOH content, NCO/OH molar ratio, and molecular weight (M-n) of PBA on the properties of APU dispersion and its cast film were studied. Dynamic light scattering results revealed that these high solid content dispersions shown broad particle size distributions as well as bimodal. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA) results showed that as the hard segment content increased, the melting point (T-m) of the APU cast film increased, but the glass transition temperature (T-g) did not show significant alteration, when a PBA lower than 1000 M-n, was used, the APU exhibited faint soft-segment crystallization and tended to form amorphous polymer. Tensile and T-peel strength tests attained excellent mechanical properties, such as a maximum Young's modulus of 166 MPa and the elongation at break reached to 2000%. T-peel strength test (PVC/PVC) yielded a maximum peel strength value of 8.8 N/mm. (c) 2007 Wiley Periodicals, Inc.