RETURN TO DE FEIJTER AND VRIJS FORMULA FOR LINE TENSION AT THIN LIQUID-FILMS

A mechanical model description is presented of the transition zone bet ween a thin soap (emulsion) film and its adjacent meniscus. The mechan ical state of the system is described by introducing three surfaces of tension - two of them are at the surfaces of the film and the transit ion zone and constant surface tensions are attributed there; the centr al surface of tension divides the distance between the other two surfa ces of tension in inverse ratio of their surface tensions. The disjoin ing pressure like the capillary pressure acts always normal to the pha se surfaces of tension. This model is applied for calculating the line tension of the contact line film/meniscus. Thus a new way of deriving the formula of de Feijter and Vrij for line tension at thin liquid fi lms is presented. The asymmetric case of emulsion films is also consid ered.