Role of Surfactants in Droplet Deformation

If the y-gradient can become large enough, it will arrest the interface. If the surfactant is applied at one site of the interface, a y-gradient is formed that will cause the interface to move roughly at a velocity given by. 

Interfacial tension gradients are very important in stabilising the thin liquid film that is located between the droplets and which is very important at the start of emulsification (films of the continuous phase may be drawn through the disperse phase and collision is very large). The magnitude of the y-gradients and of the Marangoni effect depends on the surface dilational modulus s, which for a plane 

For conditions that prevail during emulsification, e increases with m, and is given by the relationship. 

Typically, SDS shows a much higher e-value when compared with p-casein and lysosome, mainly because the value of F is higher for SDS. The two proteins show a difference in their e-values which may be attributed to the conformational change that occurs upon adsorption. 

The factor 2 follows from the fact that two interfaces are involved. Taking a value of Ay = 10 mN m , the stress amounts to 40kPa (which is of the same order of magnitude as the external stress). 

During emulsification, s is dominated by the magnitude of the denominator in Eq. (6.22) because C remains small. The value of dmc/dT tends to go to very high values when F reaches its plateau value e goes to a maximum when me is increased. 

Another important role of the emulsifier is to prevent coalescence during emulsification. This is certainly not due to the strong repulsion between the droplets, 

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