Extensional Properties of a Dilute Polymer Solution Following Preshear in Microgravity

The Shear History Extensional Rheology Experiment (SHERE) is an International Space Station (ISS) experiment designed to study the effects of a preshear history on the transient extensional viscosity of a dilute polymer solution in a uniaxial stretching flow. The absence of gravitational body forces allows us to measure the capillary thinning of the fluid filament after cessation of the extensional deformation without sagging of the liquid bridge. Understanding the deformation and thinning of polymeric solutions in complex flows containing both shearing and extensional kinematics is particularly relevant in a wide variety of industries, including fiber-spinning, injection molding, food and consumer product processing, as well as future `containerless processing' operations. The SHERE experiment offers the ability to preshear the test samples before imposing a uniaxial stretching flow in order to explore the impact of this preshearing on the sample extensional viscosity and elastocapillary thinning. After the SHERE main hardware was launched to the ISS on-board Shuttle Mission STS-120, two batches of 20 and 25 fluid samples were successively launched on-board Shuttle Missions STS-123 and STS-126. The SHERE experiments were performed by astronauts Greg Chamitoff and Mike Fincke between July 2008 and January 2009. In this talk, we will focus on the main results obtained for a well-characterized dilute polymer solution and compare them to ground-based experiments. In addition, we will show potential applications of the current microgravity experimental findings.