Polymer solutions are important for a variety of purposes. In Chapter 3 dilute polymer solutions were required for the determination of molecular weights and sizes.
A wide range of modern research as well as a variety of engineering applications exist for polymers in solution (see Table 4.1). These range from reducing turbulent flow in heat exchangers to the production of paints, varnishes, and glues.
PHASE SEPARATION AND FRACTIONATION
4.1.1 Motor Oil Viscosity Example
As an example, the maintenance of near constant viscosity in motor oils over wide operating temperatures will be considered. In the old days, people changed their oil for summer and winter use; otherwise, at low temperatures the summer oil would become too "thick," the reverse being true for using winter oil in summer. Of course, "thickness" in this case refers to viscosity. The viscosity of today's motor oils bears designations such as SAE 5W-30. According to crankcase oil viscosity specification SAE J300a, the first number refers to the viscosity at -18°C, and the second number at 99°C. The closer the two numbers are, the less the temperature variation of the viscosity.