Techniques for determining contact angle and wettability of powders

• Common methods for powder wettability determination are summarized.
• Sessile drop, Wilhelmy plate, and Washburn capillary rise are the most common methods.
• Washburn capillary rise (WCR) experimental setups are extensively discussed.
• Accurate wettability by WCR depends on suitable experimental details.
• Details include tube material/size, support, wetting liquid, mass uptake, and particles.

This review summarizes some common methods for determining the wettability of powders, especially the contact angle that a liquid would form on powders. The sessile drop, Wilhelmy plate and liquid penetration methods are then briefly compared, especially on the advantages and disadvantages of these techniques. The later part of the review summarizes some experimental details in determining wettability of powders utilizing liquid penetration into a packed column or the Washburn capillary rise (WCR) method based on liquid mass uptake. The discussion is focused on the selection of capillary tube for packing, bottom support, powder properties, reference wetting liquid, and packing method. How each of these parameters influences mass uptake and subsequent wettability determination are also presented, followed with the applicability of mass based WCR for determining the wettability of some powders. The intent of this review is to provide researchers a guide on the proper selection of the method and then the associated details when they apply the mass based WCR experiments for deducing the wettability information of the powders of interest.

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