Flow-induced structure of immiscible polyolefin blends under steady shear flow studied by small angle neutron scattering

The flow-induced structure of immiscible polyolefin blends under steady shear flow was studied by small angle neutron scattering. The sample used was a 3:7 blend (by weight) of i-polypropylene and ethylene-octene random copolymer. At low shear rates, anisotropic scattering was observed on a two-dimensional detector in through-view measurements (incident beam perpendicular to the flow). The intensity was stronger in the direction perpendicular to the flow direction. In edge-view measurements (incident beam parallel to the flow), no anisotropy was observed. At higher shear rates ( > 50 sec ^-1 ) , the anisotropy became very weak but the intensity itself became rather strong. A simple explanation of these observations can be given by assuming the existence of string-like domains at low shear rates and their splitting at high shear rates. This idea can be supported by the low interfacial tension between two polyolefins.