Synthesis and characterization of cycloaliphatic diepoxide crosslinkable core-shell latexes

Surfactants, varying in their chemical composition and hydrophobic behavior, are used in the formulation of a waterborne coating. These differences influence their aggregation in micellar structures, their interaction with associative thickeners, and in particular, the synergies present in their competitive adsorptions on the disperse phases in a waterborne coating. Adsorption of HEUR thickeners on latexes and the ability of surfactants to displace them from those surfaces is an important variable in the dispersion’s viscosity. With large particle latexes, viscosity increases arise primarily from the network built through the interaction of HEURs with surfactants in the aqueous phase. Fluorescence is used to verify the mechanism by which surfactants enhance associative thickener viscosities. That is best achieved with nonionic surfactants, because of their synergies with large hydrophobe HEURs at low concentration. With decreasing latex particle size the adsorbed species is an important contributor to the dispersion’s viscosity through its contribution to the latex’s effective volume fraction increase and when the size of the adsorbed HEUR is matched to the separation distances of the latex at 0.25 volume fraction. Achieving controlled shear-thinning behavior in small particle size latex paints with the economic constraints on the amount of HEUR required to obtain 90 KU viscosities are discussed.

Surfactant behavior and its influence on the viscosity of associative thickeners solutions, thickened latex dispersions, and waterborne latex coatings

Core-shell latexes (LAs) designed for crosslinking with cycloaliphatic diepoxide were synthesized. The core contained methyl methacrylate (MMA), butyl acrylate (BA), and 2-hydroxyethyl methacrylate, and the shell was prepared with MMA, BA, and methacrylic acid. The crosslinker was coemulsified with the monomer and added during the LA preparation or after the polymerization either as an emulsion or in an organic solvent. The morphology of the LA was studied with atomic force microscopy and transmission electron microscopy. We used titration to establish the acid distribution. The water absorption and tensile and viscoelastic properties of the LA films were investigated as a function of the addition mode of the cycloaliphatic diepoxide crosslinker. The solution approach generally provided better mechanical properties than the emulsion approach, and the addition of epoxide during the polymerization lowered the water adsorption and hardness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 245–257, 2003

Effect of the addition mode of cycloaliphatic diepoxide on the morphology and film properties of crosslinkable core-shell latex

In the characterisation of latices conductometry is the technique most commonly used. In this paper it is shown that a thorough characterisation of latices is possible based mainly on potentiometric titrations in aqueous and non-aqueous media and on spectrophotometry. Results obtained with these techniques in the study of acrylate latices prepared with nonylphenolpolyethyleneoxidesulphate as the emulsifier are presented. It is shown that this type of emulsifier is subjected to considerable hydrolysis during the emulsion polymerisation process.

A. Abel

Papers

Characterisation of acrylate latices by potentiometry and spectrophotometry