Determination of the wettability of powders by the Washburn capillary rise method with bed preparation by a centrifugal packing technique

Abstract

The Washburn capillary rise method is a standard technique for determining the wettability of powders expressed as a contact angle. The method requires the preparation of two identical beds of powder. One of these beds is used to follow the capillary rise with a perfectly wetting liquid (contact angle = 0) giving access to a bed structure parameter. The other bed is used with the liquid of interest (contact angle not = 0) and the capillary rise data is analysed using the previously determined structure parameter to obtain the contact angle. In the experiments reported here we have used a centrifugal packing technique to prepare beds of powder. This gives reproducible packings and also allows a certain degree of control of the bed porosity. In addition the air permeability of the beds is also determined prior to the capillary rise experiments. The results show that the value of the contact angle of a powder determined by the Washburn method depends on the porosity of the powder bed, and that the structure parameter can be determined from the air permeability using the Kozeny-Carman expression.

Effect of Surface Properties of Iron Ores on their Granulation Behavior

“…The range of the early stage of penetration was neglected since it is governed by inertial forces with very fast rates of liquid uptake, expanding the range of calculations beyond 150 s results in high errors in contact angle determination due to increasing deviation from linearity, Table 1 shows contact angles of four iron ores calculated by formula (1). [11][12][13] . …”

“…In this work, the determination of contact angles of ores by liquid penetration rate is used. 11,12) The aim of this study was to investigate the permeability of the green granules bed of nine groups of iron ore sinter mixes, and the particular emphasis was given to examining how the characteristics of the ores such as surface roughness, shape and wettability affect granulation and the resulting bed properties.…”

Experimental and Computational Methods Pertaining to Surface Tension of Pharmaceuticals

“…The wetting of small particles and porous materials is a very important phenomenon in pharmaceutical technologies for wettability studies of drug powder and drug manufacturing with related processes. There are a number of available methods, however capillary rise method is a routine measurement for contact angle study of powder and porous materials (Ramírez-Flores et al, 2010;Galet et al, 2010;Xue et al, 2006). Contact angle method for powders can be classified into those which require compaction, and those which utilize penetration of liquid through an uncompacted bed.…”

Functionalization of polymer powders for SLS-processes using an atmospheric plasma jet in a fluidized bed reactor

“…To investigate the influence of the treatment on the polymer particles, the contact angle of the powder is measured in a Krüss Tensiometer K12 (Krüss GmbH, Germany) by applying the Lucas-Washburn-Equation [10]. For this measurement a specified quantity of powder is filled in a glass tube with a filter paper at the bottom.…”