Self-Cross-Linking Hybrid Protein-Acrylic Latexes through the Keto-Hydrazide Reaction

Proteins are promising raw materials that can be combined with polyacrylates to produce sustainable latexes for film-forming applications. However, they have low resistance to water and organic solvents, which could be improved by cross-linking the film during the drying process. In this work, self-cross-linking hybrid protein-acrylic latexes were produced through semicontinuous copolymerization of an acrylic formulation containing different amounts of diacetone acrylamide (DAAM) using zein-casein bioparticles as seed. The film cross-linking occurred through the reaction between the ketone groups of DAAM and the hydrazide group of adipic acid dihydrazide during film drying. The cross-linked films exhibited superior resistance to water and organic solvents, as well as better mechanical properties compared to the un-cross-linked one. Finally, desirable properties, such as excellent film-forming ability, high blocking resistance, and low opacity, highlight the suitability of these latexes as candidates for the development of a next-generation of eco-friendly coatings.