On Rupture of a Thinning Film of Non-Newtonian Power Law Liquid†

A linear stability analysis of a thinning film of non-Newtonian power law liquid has been employed to predict the critical thickness of rupture of films with immobile interfaces experiencing only van der Waals interactions. The assumption of immobile interfaces makes the above analysis equally applicable to the stability of foam as well as emulsion thin films. Psuedoplastic liquid thin films are found to be significantly less stable than Newtonian films. Power law liquid thin films are more stable for liquids with larger values of power law exponents and larger values of consistency indices. The critical thickness of film rupture is very sensitive to the power law exponent. As expected, the critical thickness of film rupture increases for stronger van der Walls interactions as well as for smaller surface tensions, these effects being more pronounced for psuedoplastic liquid films than their Newtonian counterparts.