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Thickening of structured acrylate latices with butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid copolymer showed that association of the thickener based on hydrophobically modified ethoxylated polyurethane (HEUR) with the latex particles was considerably affected by hydrophobicity of the particle shell surface controlled by various content of styrene units in the copolymer. In contrast, the thickening mechanism of hydrophobically modified alkali-soluble emulsion (HASE) and, consequently, the viscosity of thickened materials depends predominantly on the excluded volume of swollen thickener particles and the influence of the styrene content is negligible. [Copyright &y& Elsevier]

Abstract: The rheological study of acrylate latices showed that an important factor influencing thickening with hydrophobically ethoxylated urethane (HEUR) associative thickeners is the effective hydrodynamic volume of latex particles, which in concentrated latices controls the remaining volume available for the thickener macromolecules. Thus, the larger volume corresponding to a smaller size of alkalinized swollen particles of ethyl acrylate/acrylic acid copolymers with “hard” comonomers methyl methacrylate or styrene leads to lower density of network structure of the thickener bridging the latex particles and, consequently, to lower viscoelasticity of the thickened material. [Copyright &y& Elsevier]