Water-based anti-smudge NP-GLIDE polyurethane coatings

Abstract

An environmentally friendly water-based NP-GLIDE polyurethane (PU) coating has been developed. The term NP-GLIDE as described herein suggests that water, organic solvents, or contaminants in these liquids have no problem to glide down the coating or that the coating bears nano-pools of a grafted lubricating ingredient for dewetting enablement. To prepare a coating, a blocked polyisocyanate and a graft copolymer polyol-g-PDMS consisting of a water-dispersible polyol backbone and poly(dimethyl siloxane) (PDMS) side-chains were co-dispersed in water containing 5.0 vol.% of dipropylene glycol monomethyl ether, cast onto a substrate to evaporate the solvent, and then thermally cured. As the liquid-like PDMS is covalently bound to the polyol backbone, it could not undergo macrophase separation and instead formed nano-pools with diameters of less than 30 nm throughout the polyurethane matrix. Meanwhile, the surface of the coating changed from solid-like to liquid-like due to the surface enrichment by PDMS. Of the three families of polyol-g-PDMS samples that were synthesized and evaluated, only one of these polyol-g-PDMS families yielded NP-GLIDE coatings with superior properties. All of the test liquids with surface tensions above 23 mN/m readily and cleanly slid down the optimized coatings that had a hardness of 3H. Moreover, both marker ink and a commercial paint contracted on these coatings and the contracted ink could be readily and cleanly removed with tissue paper without leaving any traces behind. Moreover, the ink contraction capability was maintained after the writing and erasing test had been performed for more than 30 cycles. The environmental friendliness of the coating formation process and the superior anti-smudge performance of the resultant coatings suggested that they have excellent potential for practical applications.