Rupture energy of a pendular liquid bridge

International audienceWe propose a simple expression for the rupture energy of a pendular liquid bridge between two spheres, taking into account capillary and viscous (lubrication) forces. In the case of capillary forces only, the results are in accordance with curve fitting expressions proposed by Simons et al. [2] and Willett et al. [5]. We performed accurate measurements of the force exerted by liquid bridges between two spheres. Experimental results are found to be close to theoretical values. A reasonable agreement is also found in the presence of viscous forces. Finally, for small bridge volumes, the rupture criterion given by Lian et al. [10] is modified, taking into account additional viscous effects

Direct osmotic pressure measurements on partially neutralized poly(acrylic acid) gels

We present a new experimental device to measure the osmotic pressure in gels. The system has been tested on partially neutralized poly(acrylic acid) gels. The variation of the osmotic pressure with polymer concentration, Φ, and ionization degree, α, is linear, provided that α is not too high (I.e. the counterions do not condense on the chains). These results are in good agreement with theoretical models and with compressibility measurements obtained by light scattering experiments. The very charged gels are also studied, and the results are discussed in the frame of existing theories and experiments

Coexistence of Liquid and Solid Phases in Flowing Soft-Glassy Materials

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