Effective molecular weights, HEUR

In some cases, it is not practical to make a one-thickener base paint. Some of the very low effective molecular weight HEURs are so inefficient... 

Table I compares typical test results for low-, mid-, and high-effective molecular weight thickeners in a vinyl-acrylic latex paint. Many of the same trends are present with cellulosic and HE UR thickeners when the effective molecular weight designation for HEUR thickeners is used. As the effective molecular weight of an HEUR increases, Stormer thickening efficiency, roller spatter, and water resistance increase, whereas ICI viscosity decreases. The major difference between these two thickener types is in their low-shear behavior. As effective molecular weight increases, cellulosic paints improve in leveling and decrease in sag resistance. HEUR paints decrease in leveling and improve in sag resistance. Other property differences between these two thickener types are highlighted in Table II.

Blend Ratio, HEUR Effective Molecular Weight, and HEC Molecular Weight. Table HI presents data that show the effect of these variables on the clear-liquid separation that occurs in a vinyl-acrylic flat after 1 month of shelf-aging. Generally, clear-liquid separation was greatest... 

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