Plastics have been highly successful in replacing such conventional materials as metals, glass, and wood in a wide variety of applications due to their special property advantages such as high strength-to-weight ratio, corrosion resistance, versatility of part design, and ease of fabrication. The various plastic products are formed by processing polymers by one of the number of available tech- niques such as injection molding, compression molding, blow molding, profile extrusion, and sheet extrusion followed by stamping or thermoforming. In all these processes, the molten polymer is subjected to a wide range of shear rates and temperatures. During deformation, viscous heat is dissipated due to the friction between the highly viscous polymer melt and the various parts of the processing equipment that it comes in contact with. The viscous heat dis- sipated leads to a temperature rise, resulting in an offset of the setting of the extruder temperature profile with respect to throughput rate or screw speed. For all high output rate operations, it is essential to know the viscous heat gen- erated in order to appropriately design the conventional extruder screw so as to minimize the temperature increase in the process of plastication and to optimize the extruder temperature profile with respect to the throughput rate or screw speed. Viscous heat estimation is also critical when processing heat- sensitive polymers so as to maintain the melt temperature well below the de- gradation point.