# Difference between revisions of "Contact angle associated with thin liquid films in emulsions"

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==Results== | ==Results== | ||

− | The tension of the film, γ<sub>f</sub> | + | The tension of the film, γ<sub>f</sub> is related to the bulk interfacial tension γ by |

[[image:emulsion1.png]] | [[image:emulsion1.png]] | ||

+ | |||

+ | where h is the film thickness, h<sub>e</sub> is the equilibrium thickness and π is the disjoining pressure. Whenever ΔF < 0, the two bulk surfaces will, on macroscopic scale, intersect an angle 2θ (see figure 1), such that | ||

[[image:emulsion2.png]] | [[image:emulsion2.png]] | ||

+ | |||

+ | and therefore | ||

[[image:emulsion3.png]] | [[image:emulsion3.png]] | ||

+ | |||

+ | ΔF essentially determines whether the oil droplets will repel or spontaneously flocculate as in figure 2. For ΔF < 0, we can precisely determine the value of ΔF just by measuring the macroscopic contact angle by equation (3). | ||

[[image:emulsion4.png]] | [[image:emulsion4.png]] |

## Revision as of 18:37, 24 November 2011

## Introduction

The surface tension of liquid film can be very different from the surface tension of the liquid in bulk, because of contributions from the disjoining pressure. The authors described a method to measure the surface tension of a liquid film easily by measuring the contact angle formed between the film and the plateau border. The authors showed how the contact angle is related to the disjoining pressure and demonstrated how temperature and different salt concentrations changes the surface tension of liquid film.

## Results

The tension of the film, γ_{f} is related to the bulk interfacial tension γ by

where h is the film thickness, h_{e} is the equilibrium thickness and π is the disjoining pressure. Whenever ΔF < 0, the two bulk surfaces will, on macroscopic scale, intersect an angle 2θ (see figure 1), such that

and therefore

ΔF essentially determines whether the oil droplets will repel or spontaneously flocculate as in figure 2. For ΔF < 0, we can precisely determine the value of ΔF just by measuring the macroscopic contact angle by equation (3).

## Personal Thoughts

## References

1. Contact angles associated with thin liquid films in emulsions, Aronson and Princen, Nature 1980