Properties of aqueous polyurethane dispersion modified by multi-epoxy crosslinkers

The carboxyl groups of anionic aqueous polyurethane dispersions (PUD) serve as an internal emulsifier stabilizing PUD and cause the PUD film exhibit high hydrophilicity. In order to improve the performances of PUD film, PUD were crosslinked by sorbitol glycidyl ether (GE-60) and tetraglycidyl meta-xylene diamines (GA-240), respectively. The effect of crosslinkers on the water-resistance, alcohol-resistance, hardness, and thermal stability of PUD films were studied. The FTIR spectrum showed that the carboxyl and amino groups of PUD react with epoxy groups of GA-240 and GE-60 during the drying process of PUD. The properties of PUD films indicated that the water solvent-resistance, flexibility and cold crack resistance of PUD films cured by GA-240 and GE-60 are improved impressively; GA-240 also increases the gel content and hardness of PUD films up by 89.0% and 0.83, respectively, and the optimal mass ratio of GA-240 and PUD(m(GA-240):m(PUD)) is 0.02, while the corresponding mass ratio of GE-60 and PUD (m(GE-60):m(PUD))is 0.012.The TGA curves determined that the thermal stability of PUD crosslinked by GA-240 and GE-60 is better than that of PUD.