Study of the drying behavior of model latex blends during film formation: Influence of carboxyl groups

Latex blending is a strategy used to eliminate volatile organic compounds f rom latex coatings formulations. This paper focuses on the study of the dry ing kinetics of model hard/soft latex blends and the influence of the prese nce of carboxyl groups on these particles as well as the extent of neutrali zation of the carboxyl groups with different bases. The model latex blend w as comprised of clean, well-defined polystyrene hard and poly(n-butyl metha crylate-co-n-butyl acrylate) soft latex particles with monodisperse particl e sizes, homogeneous copolymer composition, and independent control of part icle size and carboxyl group content. Drying models are discussed. It was f ound that the presence of carboxyl groups in the latex particles retarded t he drying rate of the model latex blends. When the carboxyl groups present in the latex blends with low carboxyl group coverage on polystyrene particl es were neutralized by using ammonium hydroxide or sodium hydroxide, the dr ying rate increased. When the carboxyl groups present in the latex blends w ith a high carboxyl group coverage on polystyrene particles were neutralize d by sodium hydroxide, potassium hydroxide, or cesium hydroxide, the drying rate first decreased and then increased as the extent of the neutralizatio n increased. However, the neutralization of these carboxyl groups with ammo nium hydroxide increased the drying rate of the latex blends within a broad range of neutralization conditions (from 0 to 100%). A cluster model was p roposed to explain these phenomena.