Perpendicular orientation between dispersed rubber and polypropylene molecules in an oriented sheet

Abstract

An immiscible blend of isotactic polypropylene (PP) and ethylene-butene-1 copolymer (EB) (PP/EB = 70/30) containing a small amount of N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide as a nucleating agent for β-form crystals was prepared by T-die extrusion. We successfully prepared an extruded sheet in which the orientation of the PP molecules is perpendicular to the deformation of the EB particles, i.e., the β-form crystals of PP are predominantly oriented perpendicular to the flow direction of the sheet plane (the transverse direction, TD), whereas the EB droplets are strongly deformed in the flow direction. It should be noted that EB barely affects the crystalline form and orientation of PP. This extraordinary structure provides unique mechanical anisotropy. The tear strength of the TD sample is significantly enhanced by the anomalous crack propagation in the machine direction (MD). Moreover, the anisotropy in tensile properties, such as the Young’s modulus, yield stress, strain at break, and dynamic tensile modulus, is reduced. An immiscible blend of isotactic polypropylene (PP) and ethylene-butene-1 copolymer (EB) containing a small amount of N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide as a nucleating agent to generate β-form crystals was prepared by T-die extrusion. We successfully prepared an extruded sheet in which the orientation of the PP molecules is perpendicular to the deformation of the EB particles. It is suggested that EB barely affects the crystalline form and orientation of PP. Since this sheet containing a large amount of β-form crystals exhibits an extraordinary structure, unique mechanical anisotropy is obtained.