It was investigated the effect of the method of obtaining polymer composites based on the blend of polymers over a wide range of their ratios on the rheological and physical-mechanical properties. The composites were prepared (using pressing or pressure die casting) on the basis of secondary polypropylene (PP) and the following polymers: 1) ultra high molecular polyethylene (UHMPE); 2) ethylene propylene diene monomer (EPDM); 3) secondary low pressure polyethylene (LPPE). Pressing was carried out on an automatic hydraulic press "AutoMH-NE" (Carver, the USA) at 210°C and endurance under pressure of 7000 kgfs within 3 min. Injection molding was performed using a Babyplast automatic molding machine of the horizontal type with an injection volume of up to 15 cm3. In both cases, the compositions also went through a stage of the preliminary mixture at the laboratory station (plastograf) of "PlastographEC" (Brabender, Germany) within 15 min at a load of 200 N. Estimation of rheological properties of the polymer composition melts was performed using a Haake Mars III rheometer. The deformation-strength properties were studied according to the State Standard GOST 11262-80 with a tensile testing machine "Shimadzu AGS-X". Using the data of relative rheometry, it is determined for all the systems studied (blends PP with UHMPE, EPDM, and LPPE) that variation of the maximum torque with composite composition is non-additive. This seems to be due to the occurring phase reversal. The present fact finds its support when performing rheological investigations using absolute rheometry. It is shown that variations in the phase structure of composites occurring in the phase reversal area lead to the corresponding changes in the deformation-strength properties of composites.