Rheology: Theory and Applications, Volume 5 focuses on overtly fluid behavior of polymers, including the theory of large deformations, thermoelastic effects, elastic phenomena observed during the extrusion of polymeric melts, and theories of the structure of liquids and glasses. The selection first elaborates on the application of large deformation theory to the thermomechanical behavior of rubberlike polymers and unstable flow of molten polymers. Discussions focus on the mechanism proposed for unstable flow, ripple and associated effects, direct observation of waviness phenomena, empirical behavior of porous, unfilled, and filled rubberlike polymers, and problems connected with the interpretation of mechanical response parameters. The text then examines elasticity effects in polymer extrusion and strength and extensibility of elastomers. The publication takes a look at free volume and polymer rheology and studies of the deformation of crystalline polymers. Topics include the contribution of the two orientation processes to the birefringence, deformation of superstructure, rate of orientation of crystalline regions, free volume and physical state, glass transition and free volume, and reappraisal of time-temperature superposition. The manuscript also elaborates on the deformation and dissipative processes in high polymeric solids and the thermodynamics of deformation. The selection is a vital source of data for researchers interested in the theories and applications of rheology.