Advances in emulsion polymerization for coatings applications: Latex blends and reactive surfactants

Abstract

The utilization of latex blends to prepare zero-VOC coatings and the use of reactive surfactants in emulsion polymerization are two advances in waterborne technology that are of increasing interest to coatings formulators. The first part of this paper focuses on an investigation of the influence of the interface between high and low Tg latex particles on the gloss and surface morphologies offilms obtained from model latex blends. Gloss was influenced by the concentration of carboxyl groups present on the surface of the latex particles (optimal concentration for maximum gloss = 13% on the high Tg particles, the degree of neutralization of these groups (higher gloss with increased extent of neutralization), the type and concentration of the neutralizing base (higher gloss for stronger bases), and the presence of added surfactant (higher gloss with added surfactant). Gloss was found to be correlated with the surface smoothness of the film. The kinetics, partide size, molecular weight, and location of the reactive surfactant after polymerization, as well as the contact angle of films prepared from these latexes, are examined in the second part of this paper. The polymerization rate profiles were similar to those obtained using a conventional surfactant; however, the dependency of the rate on the number of particles was significantly lower. The amound bound increased and the molecular weight decreased with increasing surfactant concentration.