Conventional techniques for contact angle measurements do not perform well for small particles. The equilibrium capillary pressure technique (ECP) consists in measuring the pressure required to prevent liquid penetration into a packed bed of particles and calculating the contact angle from a simple model, namely the equilavent capillary model. The ECP is well suited for the measurement of advancing contact angles. In its most convenient version the capillary pressure is measured for two different liquids (one of which is fully wetting and thus allows the calculation of the effective capillary radius). The use ECP to obtain the receding contact angle on powders has been developed. The major difference bertween a liquid penetrating a porous bed and retreating from it is that liquid pockets are left behind in the receding case. Effectively, this reduces the porosity of the packed bed. The volume fraction of the retained liquid apparently depends on the surface tension of the liquid but is only marginally affected by the wettability and size fraction of the particles. Therefore a simple procedure for the determination of the receding contact angle, based on the use of a calibrating liquid, is outlined and verified. The approach gives realistic values for the receding contact angle. / Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2005.
| Identifer | oai:union.ndltd.org:ADTP/266969 |
| Creators | Stevens, Nathanael I. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | copyright under review |
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