Improving the reliability of powder contact angles with the Washburn Direct method and a tool for uniform sample preparation

In many industrial sectors, homogeneous mixtures between powders and liquids, so-called dispersions, must be produced. For ready meals, for example, spice powder is stirred-in on a large scale, in paint formulations pigments are the most important component, and in pharmaceuticals powders are often mixed with water by the patient himself before administration. Whether these processes are successful or whether lumps are formed depends on the wettability of the powder.

The powder contact angle, which reflects the wettability, has been measured for a long time using the Washburn sorption method. This Application Report uses the more recent Washburn Direct approach for analyzing cellulose microcrystalline powder as a model sample. To ensure the particularly important homogeneity of the samples, a special preparation set was utilized. We could show that the thus measured water contact angles exhibit high reproducibility, which is hard to achieve with the classic Washburn approach and conventional preparation methods.