Rheology of Polymer Melts

Rheology is the field of science that studies fluid behavior during flow-induced deformation. Of the variety of materials that rheologists study, polymers have been found to be the most interesting and complex. Polymer melts are shear-thinning, viscoelastic, and their flow properties are temperature dependent. Viscosity is the most widely used material parameter when determining the behavior of polymers during processing. Because the majority of polymer processes are shear rate dominated, the viscosity of the melt is commonly measured using shear deformation measurement devices. However, some polymer processes, such as blow molding, thermoforming, and fiber spinning, are dominated by either elongational deformation or by a combination of shear and elongational deformation. In addition, some polymer melts exhibit significant elastic effects during deformation. This chapter will concentrate on shear deformation models but, for completeness, elongational flows, concentrated suspensions, and viscoelastic fluids will also be covered. Modeling and simulation of polymer flows will be briefly discussed. For further reading on rheology of polymer melts, the reader should consult the literature [1–6]. For more detail on polymer flow and processing simulation the literature [7, 8] should also be reviewed.