Abstract
We examined the elongational deformation of concentrated suspensions using a viscoelastic fluid as a solvent. The stretch deformation subjected in fluid was given by a filament stretch method. Test fluid was mixture of potato starch and PAA1.0wt% with a ratio of concentration of 1:1. In the results in elongational deformation, it was found that the existence of solid particles in fluid affected the transient response of filament shape and force acting on fluid. Especially, at high stretch rates, the aggregation of particles occurred in a liquid filament locally, and the profile of the filament achieved to an asymmetric shape. The aggregation of particles seems to be caused by a compressive deformation in the radial direction of the filament. This result is relevant to jamming of particles reported in shear flow. Furthermore, in the evaluation of elongnational viscosity, although the results of concentrated suspension were larger than those of solvent, the difference in the stretch-thickening of elongational viscosity between both fluids was not remarkable.
