Colloidal stability of surfactant-free radiation curable polyurethane dispersions

Radiation-curable polyurethane dispersions (UV-PUDs) are colloidal dispersions whose stability is mainly ensured by the electrostatic repulsion between the negatively charged polymer particles. In this article, particle stabilization is presented in terms of the physico-chemical characteristics of the polymer dispersion and its microstructure. The phenomenon of the colloidal destabilization at higher temperature is studied by multiple light scattering, then correlated with the evolution of the particle size distributions and the measurement of the apparent critical coagulation concentration of a salt as an indication of the energy barrier at the surface of the particles. The investigation of selected chemical parameters of the polymer on the colloidal stability aims to identify the most relevant ones with an understanding of the underlying mechanism. The study underlines that UV-PUDs constitute a waterborne polymer family with its own identity, adding complexity to the traditional radiation curing chemistry. Finally, it highlights the new perspectives offered for novel environmental-friendly products with high-end performance and extended stability and robustness.