Interfacial tension release

In milk, the important interfaces are those between the liquid product and air and between the milk plasma and the fat globules contained therein. Studies of the surface tension (liquid/air) have been made to ascertain the relative effectiveness of the milk components as depressants to follow changes in surface-active components as a result of processing to follow the release of free fatty acids during lipolysis and to attempt to explain the foaming phenomenon so characteristic of milk. Interfacial tensions between milk fat and solutions of milk components have been measured in studies of the stabilization of fat globules in natural and processed milks. 

A last possibility, which has not been reported so far, is a method in which one measures the heat of reaction, which is released when drops containing component 1 coalesce with drops containing component 2. This method is only suitable in continuous operation, as otherwise the temperature rise that would occur would affect both the interaction rate and the chemical conversion rate. All other methods mentioned so far are suitable both for batch operation and for continuous operation, with a slight preference for the latter since steady-state operation probably will give more reproducible results. A limitation of all the above methods is that only the interaction rate of an aqueous dispersed phase can be measured, because of the requirement that the chemical reaction be nearly instantaneous. A further disadvantage is that the dispersed phase itself is not of uniform composition, so that the interfacial tension may not be the same for all drops, and therefore the drop size may depend on the amount and type of reactants which the drops contain. 

A low interfacial tension between the oil and the wash liquid will favour oily soil release. 

According to the classic nucleation theory, a free-energy barrier must be overcome to form a stable nucleus. The energy needed to form a crystal is proportional to the interfacial tension, y, and the surface area. However, once a nucleus is formed, there is a release of energy (latent heat) associated with the phase change. 

Figure 2 presents a schematic of one scenario in which nonionic surfactant may assist biomineralization. In this situation micellar nonionic surfactant has solubilized HOC from soil. As microorganisms deplete aqueous-phase HOC via mineralization, the micelle releases HOC to solution. HOC exit rates from micelles may be significantly faster than HOC desorption rates from soil, and this condition thereby potentially enhances the availability of HOC to the microorganism. Other researchers (25, 28) suggested that surfactants may make HOCs more available for microbial attack in soil by decreasing the interfacial tension between the compound and water. 

The elasticity of emulsion droplets comes from the interfacial tension of the oil-water interface. When a strain is exerted on the droplets, their shape is changed and the area of the interfaces increases, storing energy that is released when the droplets recover their initial shape [79]. The energy scale that controls the cost of small deformations is the surface energy FT , where F is the interfacial tension and R the radius of the droplets. 

In contrast to thermodynamically stable microemulsions, nanoemulsions can be highly efficient in releasing oily materials. Indeed, they are highly metastable the droplet size is small, but the interfacial tension is not so small. This results in the Laplace pressure inside the droplets being very high. Metastability is due to the activation energy required for two droplets to merge. 

Chemical flooding involves the injection of a surfactant solution that can cause oil-aqueous interfacial tension to drop from about 30 mN m to near-zero values on the order of 10 -10 mN m , allowing spontaneous or nearly spontaneous emulsification of the oU, with an increase in the capillary number by several orders of magnitude and with greatly increased displacement and recovery of the oil [6, 10,19, 67, 75, 79-87]. The micelles present also help to solubilize the released oil droplets hence, this process is sometimes referred to as micellarflooding. Having mobilized the oil, these processes are even more efficient if the oil droplets are... 

Uses Thickener, stabilizer, suspending agent in pharmaceutical tablet coatings, controlled-release pr s., encapsulation, tablet binding Features Highly surf, active low surf, and interfacial tensions thermoplastic extrudable heat-sealable in films and coatings inert Regulatory DMF listed... 

---