Some properties of films cast from polyurethane aqueous dispersions of polyether-based anionomer extended with hydrazine

Polyurethanes as aqueous dispersions were synthesized and some mechanical properties of the casted films were analysed. Anionomers prepolymers were prepared in bulk by the reaction of poly(propylene oxide), 4,4′-dicyclohexylmethane diisocyanate and dimethylolpropionic acid. The acid group's neutralization was carried out with triethylamine. The prepolymer was divided into two parts and to one of them acetone was added. The prepolymer was then dispersed in water followed by chain extension with hydrazine producing dispersions with a 35% (w/w) solid content. The molecular weight of the polyol and the NCO/OH ratio were varied. Three kinds of dispersions were cast, as far as the presence of acetone is concerned: the pure dispersion (without acetone), with acetone (in the reaction) and with acetone added previous to casting. The mechanical evaluation of the films showed that in the second case the solvent acted as an internal plasticizer.