Interfacial Tension of Solids

This process involves extraction of fine particles from an aqueous phase into an oil phase. The effectiveness of this technique, as shown in Figure 2, is based on the stability of emulsion droplets with solid particles. If a particle is partially wetted by two immiscible liquids the particle will concentrate at the liquid-liquid interface. The thermodynamic criteria for distribution of solids at the interface of two immiscible liquids is the lowering in the interfacial free energy of the system when particles come in contact with two immiscible liquids. (12) If ygw, yWQ and ygp are the interfacial tensions of solid-water, water-oil and solid-oil interfaces respectively, and if ygQ > y + ygw then the solid particles are preferentially dispersed within the water phase. However, if ygw > ywq + ygQ, the solid is dispersed within the oil phase. On the other hand, if yWQ > ygQ + ysw, or if none of the three interfacial tensions is greater than the sum of the other two, the solids in such case will be distributed at the oil-water interface. 

The Contact Angle When the substrate is a solid, the spreading coefficient is usually evaluated by indirect means, since surface and interfacial tensions of solids cannot easily be measured directly. The method of doing this involves measuring the contact angle the substrate makes with the liquid in question. 

Interfacial Tension of Solid Polymers 12.3.1. Basic Principles... 

Li, D. and Neumann, A.W., Equation of state for interfacial tensions of solid-liquid systems, Adv. Colloid Interface Sci., 39, 299, 1992. 

OPERATIONAL RESTRICTIONS OF INTERFACIAL TENSION 5.4.1 Interfacial Tension of Solids... 

Various procedures have been proposed to indirectly assess the interfacial tension of solids. None of them is unambiguous and we refrain here from discussing them. 

The solid-liquid interfacial tensions of solids have been studied using contact angle measurements. It is one of the oldest techniques devised by Young in 1805 for studying the nature of solid surfaces. A contact angle 6 is the angle between a solid surface and a liquid meniscus, as shown in the figure beiow. 

Since the surface and interfacial tensions of solids cannot be measured directly, it is more usual to define in terms of the contact angle. From the... 

Interfacial tension of solid-liquid and solid-solid interfaces Yes (many methods, e.g. Fowkes, Hansen, van Oss-Good) Wetting, adhesion, characterization and modification of surfaces... (paints, glues...)... 

AU theories, in combination with contact angle data and information from liquid interfaces, will be used later in the book (Chapter 6) for estimating the interfacial tensions of solid-interfaces (solid-liquid, soUd-soUd) and for characterizing solid surfaces and thus for understanding important phenomena such as wetting, lubrication and adhesion. Charter 15 offers a more detailed presentation of theories for estimating the interfacial tension as weU as some comparisons between them. 

The Fowkes, Girifalco-Good and Hansen are all theories for estimating the interfacial tension of solid-liquid (and other) interfaces. Which statement is always correct ... 

The component theories, which are presented in Chapter 3, are useful for estimating the interfacial tensions of solid-interfaces (solid-liquid, solid-solid) and for characterizing solid surfaces using the experimental data for the few properties that can be measiued (liquid-gas surface tension, liquid-liquid interfacial tension, contact angle). Important equations in this context arc the Young equation... 

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