Oriented polypropylene cast films consisted of β-transcrystals induced by the nucleating agent self-assembly and its homogeneous membranes with high porosity

Abstract

In this article, the crystalline morphology of the cast film was controlled by the nucleating agent self-assembled into supramolecular structures at different temperature fields. Subsequently, the effect of crystalline morphology and orientation on porosity and uniformity of microporous membranes was investigated. The morphology of β nucleating agent (NA) networks changes from needle-like agglomerates into flower-like frameworks as PP melt temperature increases. As a result, the crystalline morphology of the cast film changed from β-transcrystals (β-TCs) organized along extrusion direction into random β flower-like crystals with the die temperature increases. Furthermore, microporous membranes with high porosity and uniform micropores distribution could be obtained from the oriented sample consisted of β-TCs. It may relate to the structure that lamellae on β-TCs were usually loosely-packed and lamellae between nearby β-TCs were mutually interdigitated. This work established a relationship between the crystalline structure of cast films and the performance of microporous membranes, which afforded a new insight to obtain PP microporous membranes with excellent performance.