INVITED REVIEW Polymer Kinetic Theories and Elongational Flowsdagger;

Steady-state elongational viscosity and various time-dependent elongational properties are generally much more difficult to measure than their shear flow counterparts. In kinetic theory, on the other hand, elongational phenomena are easier to describe than shear phenomena. A summary is presented of the available theoretical results for dilute polymer solutions, in which the macromolecules are modeled as various kinds of bead-rod-spring models, designed to simulate the orientability, distortion, and stretchability of the molecules. Then a summary of theoretical results for undiluted polymers (“polymer melts”) is given. For melts one has available two classes of theories: (i) those in which the melt is envisaged as a temporary network formed by physical junctions with various lifetimes, and (ii) those in which the melt is pictured as a collection of interacting and reptating chains. Future data comparisons will be very important in assessing the merits of the various molecular theories that have been proposed.