SOME PROPERTIES OF FILMS CAST FROM POLYURETHANE AQUEOUS DISPERSIONS OF POLYETHER-BASED ANIONOMER EXTENDED WITH HYDRAZINE

Polyurethanes as aqueous dispersions were synthesized and some mechani cal properties of the casted films were analysed. Anionomers prepolyme rs were prepared in bulk by the reaction of poly(propylene oxide), 4,4 '-dicyclohexylmethane diisocyanate and dimethylolpropionic acid. The a cid group's neutralization was carried out with triethylamine. The pre polymer was divided into two parts and to one of them acetone was adde d. The prepolymer was then dispersed in water followed by chain extens ion with hydrazine producing dispersions with a 35% (w/w) solid conten t. 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 acet one is concerned: the pure dispersion (without acetone), with acetone (in the reaction) and with acetone added previous to casting. The mech anical evaluation of the films showed that in the second case the solv ent acted as an internal plasticizer.