Methods for forming articles having improved environmental stress crack resistance

A process for the manufacture of thin-walled flexible articles comprising the steps of injection molding a polymer blend having an MFI> 10 dg / min, where the MFI is measured in accordance with ASTM D 1238, 2.16 kg; 190 ° C; and comprising at least one polymer in which said polymer includes a polypropylene having a variable tacticity within its structure wherein the polypropylene homopolymer or copolymer having a variable tacticity has a tacticity that varies within the range of between 25 and 60% of the pentad concentration [mmmm] due to the statistical distribution of stereoscopic errors in the polymer chains.