Chapter 16 - Rheological Properties of Polymer Solutions

Abstract

The rheology of polymer solutions is important in several stages of the manufacturing and processing of polymers, such as in the spinning of fibers and the casting of films from solutions, and especially in the paints and coatings industry. The rheology of a polymer solution increases with the polymer concentration. A transition exists at the so-called critical concentration (which decreases with increasing molecular mass) separating “dilute” from “concentrated” solutions. The viscosity of dilute polymer solutions can be estimated with fair accuracy. For concentrated polymer solutions, the viscosity is proportional to the 3.4th power of the molecular mass and about the 5th power of the concentration. The effects of temperature and concentration on viscoelastic properties are closely interrelated. This chapter demonstrates the validity of a time-concentration superposition. Following this, it describes a method for predicting the viscosity of concentrated polymer solutions. Furthermore, it deals with the viscoelastic properties of polymer solutions in simple shear flow. The viscoelastic properties of polymer solutions may be of practical importance, e.g., in the flow of these solutions through technical equipment. For concentrated polymer solutions, the viscoelastic properties show great analogy with those of polymer melts. For dilute solutions, the analogy decreases with decreasing concentration. Finally, the chapter sheds light on the rheological properties of solutions of lyotropic liquid crystalline polymers.