Effect of Extenders with Narrow and Broad Particle Size Distributions on the Properties of Coatings

By Rüdiger Werner

Extenders are manufactured in a wide range of finenesses enabling paint formulators to influence specific properties of the finished paint. It is necessary to know the “granulometry” or particle size distribution of the extender to select the appropriate one to achieve the desired properties.

Two extenders with practically the same top cut, but one with a broad particle size distribution curve, and the other one with a narrow or “steep” particle size distribution curve, were compared in four different coating systems. The extender with a narrow particle size distribution offered some advantages over the finer one with a broader particle size distribution.

The technical advantages of using such extenders over those with broad curves but similar finenesses, are in particular: ease of dispersion, higher opacity, haze-free gloss, shortening of the drying time, and spacing properties for titanium dioxide.