Waterborne anionic polyurethanes and poly(urethane-urea)s: influence of the chain extender on mechanical and adhesive properties

Polyurethane and poly(urethane-urea) aqueous dispersions based on 4,4'-dicy clohexylmethane diisocyanate (H12MDI), poly(propylene glycol) (PPG) and dim ethylolpropionic acid (DMPA) were synthesized, Three types of chain extende rs were used, hydrazine (HYD) and ethylenediamine (EDA), producing poly(ure thane-urea)s and ethylene glycol (EG), polyurethanes. The dispersion was pe rformed before or after the chain extension reaction, depending on the exte nder employed. The dispersions were prepared with and without the addition of acetone after the prepolymer synthesis and neutralization steps. The len gth of soft segment and NCO/OH ratio were varied. Some mechanical propertie s of cast films obtained from the aqueous dispersions, the characteristics of coating application on a wood surface and their adhesive properties were evaluated. (C) 2000 Elsevier Science Ltd. All rights reserved.