The combination of High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE) and Polypropylene (PP) is frequently found in polymer waste streams. Because of their similar density, they cannot be easily separated from each other in the recycling stream. Based on Kiesel's study , the profitability of the expanded process for recycling by blending PP/PEs amounts to $41.65. This is equivalent to a profit increase of $51.41 compared to the current recycling process and shows its huge economic potential. This study focused on the blending of PP/PEs in different ratios similar to the ones found in the recycling stream to analyze the possibility to eliminate the sorting process. In particular, it aims to maintain or improve the properties of blends of recycled materials with respect to their virgin materials. The processing conditions showed an insignificant effect on the behavior of the blends. The relationships between molecular weight, molecular weight distribution (MWD), and rheological properties of materials were determined. The rheological tests for MFI and viscosity are well suited to assess the degradation effect as well as the complex behaviors of the blends, respectively. The study clearly showed that miscisbility or compatibility of the blends in the melt could not be transferred to the solid state, because phase separation occurred. In this study, rheological behaviors, thermal properties, mechanical properties, and morphology developed in PP/PEs blends indicated the partial miscibility or partial compatibility especially for the blends containing 75 wt% of PEs. The logarithmic Rule of Mixtures is found to be successful to describe and predict the crystallinity, which is directly related to the mechanical behavior of the blends. In summary, this study shows that in regards to the service life properties, mechanical performance and the related crystallinity, no negative effect was observed within the studied parameter range. This study developed a scientifically based design methodology for polyolefin blends, starting with PP/LDPE that will allow designers to select the appropriate blend to achieve the desired properties, thus potentially increasing the upcycling and recycling rate of plastic waste in the MSW stream.