Preparation of Multiple Crosslinking Modified Waterborne Polyurethane Acrylate and Its Application in Optical Film Coating

ABSTRACT UV curable coatings were widely used in various functional optical film fields, and the waterborne UV curable coatings prepared by waterborne polyurethane acrylate (WPUA) have received widespread attention due to the environmentally friendly advantages compared to solvent‐based UV coatings. However, the properties of WPUA such as ethanol wipe resistance and abrasion resistance can hardly reach the performance of solvent‐based UV coatings. In this study, the crosslinking structure and rigid ring structure were used in pre‐chain extension before emulsification; furthermore, 3.3′‐dimethyl‐4.4′‐diaminodicyclohexylmethane (DMDC) and tetra(3‐mercaptopropionic acid) pentaerythritol ester (PETMP) were introduced as crosslinking agents after emulsification, which obtained a series of WPUA emulsions with excellent comprehensive properties, such as ethanol resistance and wear resistance, and they were successfully applied to the preparation of functional coatings of optical films. According to DFT calculations, it was found that −SH and −NH 2 preferentially reacted with −NCO instead of double bonds in the system, resulting in the introduction of crosslinking structures, rigid rings, and C−S bonds into the molecular chain. When the molar ratio of −SH to −NH 2 was 1:6, the coating's resistance to ethanol wiping reached 130 times, with a wear mass loss of 9.4 mg, exhibiting good toughness, thermal stability, and transparency.