Aqueous Acrylic-Polyurethane Hybrid Dispersions and Their Use in Industrial Coatings

By Charles R. Hegedus, Kristen A. Kloiber

Acrylic and polyurethane aqueous dispersions have been used extensively in coating applications, both independently and as physical blends. The resulting coatings display a balance of properties from the inherent characteristics of acrylics and polyurethanes. Nonetheless, these properties often fall short of those predicted from the traditional “rule of mixtures.”

In contrast, a process has been developed whereby acrylic monomers and urethane prepolymers are intimately mixed and mutually polymerized in an aqueous dispersion, thereby resulting in “hybrid” polymer dispersions. This process causes an interpentrating network (IPN) of the polymers which subsequently display unique properties compared to standard acrylic, polyurethane, or macroscopically blended acrylic/urethane dispersions.

These properties appear to be directly attributable to the acrylic-polyurethane hybrid morphology. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study film formation, coalescence, and coating surface topography. Thermal analysis was performed to characterize glass transition and thermal degradation.

The microscopy and thermal response data were used to further understand the molecular mixing and polymer morphology resulting from the hybrid polymerization and polymerization process. In addition, clear and pigmented coatings were formulated using the hybrid dispersions.

Performance properties were compared and differences were explained relative to morphological effects. These morphological effects are responsible for performance advantages over traditional binder systems in waterborne coatings.