Washburn Test

The second approach to characterize wetting considers the abihty of the fluid to penetrate a powder bed. It involves the measurement of the extent and rate of fluid rise by capillaiy suction into a column of powder, better known as the Washburn test. Considering the powder to consist of capillaries of radius R, the equilibrium height of rise... 

The contact an e or adhesion tension of a binder solution with respecd to a powder can be determined from the slope of the penetration profile. Washburn tests can also be used to investigate the influence of powder preparation on penetration rates. The Bartell cell is related to the Washburn test except that adhesion tension is determined by available gas pressure which opposes penetration. [Bartell Osterhof, Ind. Eng. Chem., 19, 1277 (1927).]... 

Figure 19. The Washburn Test for measuring wetting dynamics.

The contact angle or adhesion tension of a binder solution with respect to a powder can be determined from the slope of the penetration profile. Washburn tests can also be used to investigate the... 

Penetration of drops into powder bed Penetrating V/.y/.y/.- avvcbmpact V Washburn test Rate of penetration by height or volume Bartell cell Capillary pressure difference References Parfitt (ed.), Dispersion of Powders in Liquids, Elsevier Applied Science Publishers Ltd., 1986. Washburn, Phys. Rev., 17, 273 (1921). Bartell and Osterhof, Ind Eng. Chem., 19, 1277 (1927). 

The Washburn test requires some specialized testing equipment to perform, and an alternate test is the drop penetration time test which is more directly related to the wetting of spray drops into a granulating powder (Hapgood et al., 2003). A drop of known volume is gently placed onto a small powder bed with porosity Sf, and the time taken for the drop to completely sink into the powder bed is measured. The drop penetration time, tp, is given by ... 

The Washburn test and drop penetration time test are closely related, but the latter is simpler to perform as a screening and investigation test when developing or troubleshooting a granulation process. 

Pan et al. Dynamic Properties of Interfaces and Association Structure. New York American Oil Chem Soc Press, 1995 Washburn test ... 

Figure 15 Characterizing wetting by Washburn test and capillary rise. (From Refs. 4,23.)...

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