Enhanced water resistance in post‐crosslinked polyurethane dispersion films using ethylene glycol diglycidyl ether

Abstract A post‐crosslinked polyurethane dispersion (PUD) with excellent water resistance was prepared using ethylene glycol diglycidyl ether (EGDGE) as a crosslinker. An anionic PUD was synthesized using dimethylol propionic acid as an internal emulsifier. During the curing process of the PUD film, the hydrophilic carboxylic acid and amine groups of PUD were consumed by the reaction with EGDGE. The reduction of hydrophilic functional groups and the increase of the crosslinking density effectively improved the water resistance of PUD films. In addition, the tensile strength of the PUD film increased from 54.2 MPa to a maximum of 75.3 MPa. The crosslinked structure reduced the crystallinity of the PUD film, which led to an increase in transparency. Highlights Novel EGDGE‐crosslinked PUD films with enhanced water resistance were developed. PUD samples introduced with EGDGE indicated favorable storage stability. Crosslinking reduced hydrophilic groups, improving thermal and mechanical stability. Optimized EGDGE content (6 wt%) yielded maximum tensile strength (75.3 MPa). Transparency increased due to suppressed phase separation in crosslinked PUDs.