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ABSTRACT:

Rheology and Dispersion Stability of Latexes Thickened with HEUR

Understanding interactions among ingredients in waterborne latex paints is crucial for controlling their stability and rheology. In our prior work, ternary systems of latex-thickener-surfactant were investigated to further the understanding in this area.  A well characterized HEUR (Hydrophobically-modified, ethoxylated urethane) thickener with C18 terminal hydrophobes, two experimental latexes (a butyl acrylate/styrene – BA/Sty and a butyl acrylate/methyl methacrylate – BA-MMA, each containing a small amount of methacrylic acid) and six different surfactants were used in those studies.  Results of those studies helped map out composition ranges for the onset of bridging flocculation instabilities and syneresis as well as the formation stable, fully bridged networks.  The latex volume fraction in the previous studies was constant at 0.25.  Our recent studies focus on determining the threshold volume fractions of the above two latexes for the onset of bridging flocculation and associated syneresis.  Results available so far indicate that, at a 1% (by weight) HEUR level, the onset of flocculation and syneresis occurs at a very low volume fractions (0.02 – 0.10) of the BA/Sty and BA/MMA latexes.  At latex volume fractions around 0.25, the mixtures become stable. A comparison of results between the two latexes, their analysis, and models to explain the results will be presented.

BIOGRAPHY:

Professor Ray Fernando has been the occupant of the Arthur C. Edwards Endowed Chair in Coatings Technology and Ecology at Chemistry and Biochemistry Department, Cal Poly SLO since 2002.  He is also the director of Cal Poly’s Kenneth N Edwards Western Coatings Technology Center.  Ray Received his Chemistry B.Sc. degree in 1979 from Sri Jayewardene University, Sri Lanka.  He received his Polymers and Coatings Ph.D. in 1986 from North Dakota State University, USA.  He has fifteen years of industrial experience (3-years at Air Products and Chemicals & 12-years at Armstrong World Industries).  Ray received the American Coatings Association’s Joseph J Mattiello Award in 2018 and American Chemical Society’s Roy W Tess Award in 2019.