Extensional flow properties of dilute viscoelastic solution have attracted much attention for almost three decades. This is because extensional viscosity or relaxation time of viscoelastic solution under extensional stresses add a lot of impact on fluidity of the solution; the phenomenon is related to many industrial applications. Several techniques were proposed and many studies were conducted to measure extensional properties of polymer solutions. However, less studies were reported in the case of non-uniform solution, such as suspensions. In this study, we propose a relatively simple method to measure extensional viscosity. We adopt a syringe-shape abrupt contraction channels for the measurement; the syringe-shape apparatus is useful to contain non-uniform dilute solutions. As a first step to develop the experimental apparatus and method, we tested polymer solutions. Polymers used to prepare sample solutions were polyethylene oxide (PEO), hydroxypropyl cellulose (HPC) and polyacrylic acid (PAA). Each polymer has different flexibility, which cause different characteristics of the extensional viscosity of polymer solutions. Extensional viscosities obtained in this study detected the characteristic of each polymer solution. Extensional viscosities of PEO solution was increased by increasing extensional rates; that of HPC and PAA solution were decreased by increasing extensional rates; the tendency was explained by relaxation times of each polymer solution.

Polymer solution shows complex behaviors, which are merits and demerits in industries. For a molding process, a fiber spinning process and a turbulent drag reduction system, concentrated or dilute polymer solutions are used. In these processes, characteristics of extensional viscosity should be important. For example, increments of extensional viscosities due to polymers are considered as one of the reasons for the drag reduction occurrence. In this study, we propose a simple technique to measure the extensional viscosity of Newtonian and non-Newtonian fluids in abrupt contraction flows. The abrupt contraction flow was realized by connecting a syringe and a thin glass tube under a polarizing microscope. The syringe was filled with Newtonian and non-Newtonian fluids, and a syringe driver control to push the fluids out. The force to push the syringe was measured by a load cell to calculate the pressure added to the flow. Extensional viscosity was calculated by considering the pressure losses in the abrupt contraction flows. Water was measured as a Newtonian fluid, and polymer solution was measured as a non-Newtonian fluid. Extensional viscosity of the polymer solution measured in this study qualitatively shows the reasonable characteristics.