The blending process of stereoblock isotactic polypropylene and isotactic polypropylene (sbiPP/iPP) including a well distribution of the components (by solvent mixing), posterior hot pressing (shear mixing), and a final quenching into ice water freezing these blends at room temperature in a particular flow oriented cocrystallized structure. This structure gives rise to a birefringent pattern which is stable up to 170 degrees C when it disappears by melting. In the molten state the two components segregate destroying the original flow oriented structure. In the following cooling the iPP crystallizes in a spherulitic form and the sbiPP phase crystallizes only partially disturbed by the restrictions imposed by the iPP crystals.