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'-dicyclohexylmethane diisocyanate (H12MDI), poly(propylene glycol) (PPG) and dimethylolpropionic acid (DMPA) were synthesized, Three types of chain extenders were used, hydrazine (HYD) and ethylenediamine (EDA), producing poly(urethane-urea)s and ethylene glycol (EG), polyurethanes. The dispersion was performed before or after the chain extension reaction, depending on the extender employed. The dispersions were prepared with and without the addition of acetone after the prepolymer synthesis and neutralization steps. The length of soft segment and NCO/OH ratio were varied. Some mechanical properties 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.