Sodium Phosphate-Based Surfactants as Fluorine-Free Additives for Enhancing Block Resistance in Acrylic Waterborne Coatings

Fluorine-free antiblocking agents (ABAs) significantly reduce environmental impact compared to their fluorine-containing counterparts in waterborne coatings. However, existing fluorine-free ABAs often suffer from insufficient antiblocking performance, limiting their practical applications. In this work, we developed two fluorine-free ABAs, SiO-PO4 and Branch-C20-PO4, and incorporated them into acrylic waterborne coatings. The surface properties and block resistance efficiencies of these coatings were systematically characterized. Notably, SiO-PO4 demonstrated exceptional surface activity and achieved effective block resistance even after a 12-day storage period. X-ray Photoelectron Spectroscopy (XPS) analysis revealed that both ABAs migrated to and adsorbed on the coating surface during film formation, reducing cohesive forces generated by polar components and thereby enhancing block resistance. These results position SiO-PO4 as a promising fluorine-free ABA, demonstrating the potential of tailored phosphate-based surfactants to achieve a balance between environmental sustainability and high-performance functionality in waterborne coatings.