There has been a continuing interest in developing experimental techniques for the measurement of the rheological properties of viscoelastic fluids. As discussed in Chapter 3, reliable experimental data are needed in order to evaluate the effectiveness of a constitutive equation in its ability to predict the rheological properties of viscoelastic fluids. Also, as is presented in later chapters, a better understanding of the rheological properties of polymers is very important for the determination of optimum processing conditions, as well as for the attainment of desired physical/mechanical properties in the finished product. Further, reliable measurement of the rheological properties of polymers can be used to control polymerization reactors in industry and also to control polymer processing operations. In this chapter, we present experimental methods for measurement of the rheological properties of polymeric fluids. For this, we discuss experimental methods to determine (1) steady-state simple shear flow and oscillatory shear flow properties using cone-and-plate rheometry, (2) steady-state shear flow properties using capillary/slit rheometry, and (3) elongational flow properties of polymeric fluids. There are other rotational types of rheological instruments, such as those with concentric-cylinder and eccentric-parallel plates. However, such rheological instruments are not widely used today and thus in this chapter we do not present the principles and applications of such rheological instruments. In presenting the experimental methods for rheological measurements we refer to the fundamentals presented in Chapters 2 and 3. For further details of the experimental methods, there are monographs (Collyer and Clegg 1998; Dealy 1982; Ferry 1980; Walter 1975) that are devoted entirely to the discussion of rheological measurements. The primary purpose of this chapter is to demonstrate how the fundamentals presented in Chapters 2–4 can be used in the measurement of the rheological properties of polymeric fluids. Optical rheometry is an important experimental technique for investigation of the relationship between any microphase morphology dynamics and the rheological behavior of complex polymeric fluids (e.g., liquid-crystalline polymers), which exhibit strong chain orientation during flow (Fuller 1995).
Turbulent Flow Properties of Dilute Polymer Solutions