Aqueous polyurethane dispersions derived from various polycarbonatediols, m-di(2-isocyanatopropyl)benzene(TMXDI), and various carboxylic diols including dimethylol propionic acid (DMPA), dimethylol butyric acid (DMBA), and a carboxylic polycaprolactonediol (Placcel 205BA) were prepared by a method in which the dispersing procedure was modified to enhance the molecular weight. The NH 2 /NCO ratio during chain extension affected the molecular weight of the polyurethanes, significantly, and an optimum ratio of 0.67:1.0 was used. The molecular weight, particle size, tensile properties, and thermal properties of the polyurethane dispersions were investigated. The effect chemical structure of the polycarbonatediols on the properties shows no obvious trend, but the polyurethane dispersions derived from the carboxylic polycaprolactonediol exhibit smaller particle size and softer tensile properties when compared with those derived from DMPA and DMBA. EXPERIMENTAL MaterialsThree polycarbonatediols (L4672, L6002, and L5652) with a molecular weight of 2000 were supplied by Asahi Kasei Corporation. The polycarbonatediols are derived from 1,6-hexanediol and another diol of either 1,4-butane-

Aqueous polyurethane dispersions derived from various polycarbonatediols, carboxylic diols, and mdi(2-isocyantopropyl)benzene (TMXDI) were prepared by a solvent-free process. The dispersing procedure was investigated by Fourier transform infrared spectroscopy and it was found that the use of TMXDI could avoid the over hydrolysis of the isocyanate groups during dispersing in water. The molecular weight tends to reach a maximum around an NH 2 /NCO ratio during chain extension of 0.8 : 1.0. The particle size, tensile properties, thermal properties, and dynamic mechanical properties of the polyurethane dispersions were investigated. The properties were significantly influenced by the molecular weight of the polycarbonatediols and the chemical structure of the carboxylic diols, and described by the effects of the ionic content, miscibility between the polycarbonate soft segment and the polyurethane segment, and the soft segment content. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: E275-E282, 2012