The formation and the structure of the unique piled lamellae rows in hard elastic polypropylene have been studied by WAXD and SAXS techniques. The results show that lamellae rows are parallel to each other and perpendicular to the extrusion direction when polypropylene melt crystallized under stress field. And the higher the melting temperature of polypropylene sample, the higher melt draft ratio is required for piling up. The results also show that lamellar thickness in polypropylene is increased unde...