Filament stretching rheometry and break-up behaviour of low viscosity polymer solutions and inkjet fluids

This paper reports experimental observations on the way certain low viscosity Newtonian, polymer and inkjet fluids respond to filament stretching experiments that have been carried out using a variant of a multipass rheometer (MPR). A series of experiments were conducted where the opposing pistons of an MPR were used to provide controlled separation of two flat surfaces. Using 1.2 and 5.0 mm diameter pistons, a small quantity of test fluid was positioned between the pistons and the two pistons were moved apart at an equal and opposite velocity, thereby enabling optical interrogation of the central position of the filament that formed between the pistons faces. High speed photography followed the way the resulting fluid filament stretched and relaxed when the pistons movement had stopped. Different piston diameters, piston velocities and final piston separation were explored and the filament stretching and break-up was classified into regimes of behaviour. Approximate extensional viscosity parameters were obtained from the results. In some cases it was possible to correlate the filament stretching behaviour with the inkjet printing behaviour of a particular fluid.