Colloidally stable bio-based emulsion binders for waterborne paint applications: role of surfactant structure and monomer composition

Official URL: https://dx.doi.org/10.1016/j.porgcoat.2026.110062

Waterborne paint binder synthesis is conducted by emulsion polymerization, where the colloidal stability of the emulsion plays a crucial role in final paint film properties and performance, as well as during storage and application. Lack of colloidal stability results in broad particle-size distributions, flocculation, coalescence, or phase separation as well as sedimentation, poor leveling, uneven film formation, and surface defects in the final coating film. To prevent these defects, colloidal stability can be achieved by optimizing the balance among emulsion components, such as surfactant structure and concentration, monomer composition, and the ratio of solid:water content in formulations. This optimization provides an interplay between interfacial chemistry that yields colloidal stability. For that purpose, this study was conducted to formulate colloidally stable bio-based emulsion binders for waterborne paint applications, which were developed through a systematic investigation of surfactant structure and monomer composition. First, a pre-emulsion experiment was conducted using different types and concentrations. Then, the effect of varying monomer incorporation, replacing the styrene with bio-based ethyl acrylate (EA) and itaconic acid (IA), was studied to investigate the effect of monomer polarity and ionic functionality. The stability of the resulting emulsions was assessed by measuring particle size distribution, zeta potential, rheological behavior, glass transition temperature, freeze–thaw stability, and morphology. The results revealed that the sample CGE-16 contains the ideal balance of surfactant type, concentration, and monomer concentration, exhibiting the narrowest particle size distribution, efficient zeta potential, and appropriate morphological, rheological, and thermal behavior. Eventually, this work provides a bio-based emulsion binder with long-term colloidal stability suitable for waterborne paint applications.