AbstractThe results of the extrusiometer measurements made on a great number of different rigid poly(vinyl chloride) (PVC) compositions are analyzed. The laboratory extruders used in the experiments can be considered to be isothermic. The output rate is proportional to the extrusion speed and almost independent of the composition. The other characteristics—torque, die and back pressure—significantly depend on the composition of the compounds. The back pressure proved to be proportional to the die pressure, and thus does not give additional information. Processability is well characterized by the dissipated energy which can be calculated from the difference of the total introduced mechanical energy and the energy required to transport the melt through the capillary. The dissipated energy is closely related to the fusion characteristics of the compou