The development of micro-morphology in thermoplastic vulcanizates has a direct effect on its mechanical and physical properties. Since, there is no consistence on the mechanism of development of morphology, in this study attempt have been made to present a mechanism based on new studies on the crystallization of PP phase during morphology development. First, the crystallization of neat PP and then the crystallization of unvulcanized EPDM/PP (60/40) blend (TPO) studied and thereafter, the crystallization of proxide or phenolic vulcanized TPVs was studied. It was demonstrated that at high cooling rates the neat PP is consisted of spherulites with the nodular internal structure. In TPO the dispersed phase is nano droplets which coalesce after reduction of the shear rate and leads to co-continuous morphology and then to the phase inversion .TPO has a space filling nodular spherulites over the co-continuous PP/EPDM morphology. This is also true for TPV. Furthermore the shear and elongational fields of internal mixer have the ability to form nano droplets even at viscosity ratios larger than 4. Its appear that the co continuous structure of TPV develops after turning the rotor off. Key words Morphology, Polymer blend, Polypropylene, Ethylene-Propylene-Diene-Monomer, Thermoplastic elastomer vulcanized, thermoplastic olefin
