Tham khảo tài liệu 'fundamentals of polymer engineering part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 Reaction Engineering of Chain-Growth Polymerization INTRODUCTION In Chapter 5 we considered the detailed mechanisms of chain-growth polymerization. Expressions for the rates and average molecular weight were developed and were shown to be sensitive to the reaction temperature the initiator concentration and the presence of transfer agents. In general most polymerizations are exothermic and good temperature control can be achieved only through elaborate cooling systems. This is because most monomers and polymers have low thermal conductivity. Sometimes the desired physical and mechanical properties cannot be obtained by a homopolymer or by blending several homopolymers. In such cases copolymers are prepared several of which are commonly used in industry. This chapter discusses the reaction engineering of chain-growth polymerization. In order to form polymers of specified properties we observe that reactor temperature is a very important variable. To find this the energy balance equation must be solved along with mole balance relations of various species. In the study of copolymers the quantities of practical interest are the relative distributions of the monomers on polymer chains and the overall rates of copolymerization. With these it is possible to carry out the reactor design. 255 Copyright 2003 Marcel Dekker Inc. 256 Chapter 6 DESIGN OF TUBULAR REACTORS 1-13 A reactor design can be carried out if we know the following information 1. The rate characteristics 2. The heat and mass transfer characteristics 3. External restrictions imposed by the reactor setup on fluid flow Let us consider a tubular reactor which is normally modeled as a plug flow reactor PFR shown in Figure . The composition of the reaction mass changes along the reactor length and in the ideal reactor all fluid elements are thought to move at the same velocity or plug flow profile . Assuming a constant density process and no mixing it is possible to carry out mole balance as follows .
