RHEOLOGICAL BEHAVIOR OF VINYL ACETATE/ETHYLENE COPOLYMER LATEX COATING FORMULATIONS CONTAINING ASSOCIATIVE THICKENERS

摘要

Associative thickener related studies reported in previous literature have primarily focused on their interactions with all-acrylic latices. The focus of this study is on the interactions between vinyl acetate/ethylene (VAE) latices and non-ionic, hydrophobically modified, ethoxylated urethane (HEUR) associative thickeners. Our initial studies on rheology response of fully-formulated semi-gloss coatings containing VAE latices and HEUR-type thickeners highlighted the need to understand the VAE latex/thickener interactions. Carefully designed aqueous latex/thickener blends were employed to accomplish this objective. These studies indicate that the latex particle size and surface stabilizing moieties (i.e., surfactant type and level, presence or absence of acid monomer, etc.) are the determining factors in thickening responses, rather than the composition of the latex binder. Results indicate a wide range of viscosity responses by VAE latices depending on their particle size and surface characteristics. In prior studies, similar factors have been shown to impact the thickening mechanisms of all-acrylic latices. Viscosity data generated under carefully controlled conditions provided evidence of the importance of latex characteristics in achieving high high-shear-rate viscosities with associative thickeners.