چكيده لاتين :
Aseries of aqueous anionic polyurethane dispersions with ionic groups in the soft segments were synthesized from a polyether glycol, maleic anhydride modified castor oil, isophorone diisocyanate, and a,a-dimethylol propionic acid according
to the prepolymer mixing process. Samples were neutralized by the addition of triethylamine.
The reaction mixture was dispersed in water and the polymer chains were extended with ethylene diamine. The effect of NCO/OH molar ratio on the structure and properties of these polyurethanes were characterized by particle size analyzer, DSC, TG/DTG, IR, WAXD and tensile tester, etc. Particle size distribution becomes broader and the average particle diameter increases as NCO/OH molar ratio increases,
which is mainly attributed to the decrease in chain flexibility and increase in viscosity
of the dispersed particles. IR Study shows that the hydrogen bonding increases with increasing NCO/OH molar ratio. DSC Results identify that the phase mixing increases
when some ionic groups were incorporated in soft segments and phase separation increases as NCO/OH molar ratio increases. TG/DTG Results show better thermostability
under higher NCO/OH molar ratio that can be attributed to forming thermostable urea groups and more intermolecular hydrogen bonding. Broad scattering halos of WAXD graphs imply that all the samples are amorphous. The tensile strength and hardness of the polyurethane films increase with increasing NCO/OH molar ratio.
