A way for the recovery of plastic waste is the reprocessing. As they cannot be easily separated the reprocessing of polyolefins appears as a special case of the processing of polymer blends. In order to under-stand the basic phenomena involved in these systems, binary and ternary blends are prepared from a high density polyethylene, a linear low density polyethylene, and a random ethylene-propylene copolymer: In a first step, the interactions between the different polyolefins are characterized in laboratory experiments (differential scanning calorimetry, optical microscopy, small-angle light scattering wide-angle X-ray diffraction, mechanical properties). Then, it is shown that the original poor mechanical propel-ties of the blends can be largely improved by optimizing the processing conditions. Finally, an extrapolation of these results to veal plastic waste is presented.