Relaxation timescales in densely packed adhesive emulsions

Abstract

We experimentally investigate the relaxation time, that is, the inverse rearrangement rate, of densely packed adhesive emulsions using two complementary methods. We use a recently introduced oscillatory technique known as strain rate frequency superposition to measure the relaxation time as both a function of strain rate and packing fraction. We use microscopic imaging to study droplet dynamics in the bulk of a flowing emulsion from which we can also infer the relaxation time, again both as a function of strain rate and packing fraction. In the Material and Methods chapter We describe the custom built apparatus we developed to study droplet dynamics. Prior to our investigation of the relaxation time we measured the macroscopic rheology of adhesive emulsions using conventional techniques such as strain sweeps and flow curves. Using these techniques we obtained the yield stress, shear modulus and empirical Herschel-Bulkley parameters of our system and found them to be consistent with what has been reported in the literature.