Tham khảo tài liệu 'fundamentals of polymer engineering part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 9 Thermodynamics of Polymer Mixtures INTRODUCTION As with low-molecular-weight substances the solubility of a polymer . the amount of polymer that can be dissolved in a given liquid depends on the temperature and pressure of the system. In addition however it also depends on the molecular weight. This fact can be used to separate a polydisperse polymer sample into narrow molecular-weight fractions in a conceptually easy albeit tedious manner. It is obvious that any help that thermodynamic theory could afford in selecting solvent and defining process conditions would be quite useful for optimizing polymer fractionation. Such polymers having a precise and known molecular weight are needed in small quantities for research purposes. Although today we use gel permeation chromatography for polymer fractionation a working knowledge of polymer solution thermodynamics is still necessary for several important engineering applications 1 . In the form of solutions polymers find use in paints and other coating materials. They are also used in lubricants such as multigrade motor oils where they temper the reduction in viscosity with increasing temperature. In addition aqueous polymer solutions are pumped into oil reservoirs for promoting tertiary oil recovery. In these applications the polymer may witness a range of temperatures pressures and shear rates and this variation can induce phase separation. Such a situation is to be avoided and it can be with the aid of 374 Copyright 2003 Marcel Dekker Inc. Thermodynamics of Polymer Mixtures 375 thermodynamics. Other situations in which such theory may be usefully applied are devolatilization of polymers and product separation in polymerization reactors. There are also instances in which we want no polymer-solvent interactions at all especially in cases where certain liquids come into regular contact with polymeric surfaces. In addition polymer thermodynamics is very important in the growing and commercially important area of .
