There are summarized the experimental researches, previously performed, concerning viscous-elastic characteristics changes of PP due to recycling. There are presented, comparatively, the results for the virgin and 10 times recycled polypropylene. Using CAD-CAM it is studied the influence of the PP viscous-elastic characteristics changes due to recycling on the pipe extrusion head design, aiming to obtain a good extrusion product (expressed in the given case by the pipe dimensions stability). It resulted that it is compulsory to do experimental research to obtain the actual viscous-elastic properties of the polymer after many times recycles, because these properties affect significantly the output and the annular uniformity of the pipes thickness.