NoVOC Water-Borne Coatings Through Utilization of the Nano-confinement Effect

Abstract

Water-borne coatings are environmentally friendly compared solvent born coatings where polymer particles (the binder) and other formulation ingredients are dispersed in water. However, most water-borne coatings contain 5–10% of organic molecules like plasticizers and coalescing agents. These organic molecules evaporate from the drying coating posing an environmental burden. Many approaches have been investigated, but there is still no good working alternative for the plasticizers. The coalescing agents temporarily lower the Tg of the binder to facilitate particle deformation, after evaporation the glass transition temperature is restored to the original Tg again. A versatile alternative is to use lower Tg binders and create a “jump” in Tg during film formation. Our wok uses this nano-confinement effect, which creates a jump in Tg when the polymer chains are coming in close contact with inorganic nanoparticles surfaces, get immobilized. This close contact happens in the particle deformation stage, automatically leading to the correct timing of the two processes, particle deformation and increase of Tg. Another advantage of this approach is that no new chemistries need to be introduced. However it turns out that this approach only properly functions in a narrow window of nanoparticle loading.