Formation of oriented β‐transcrystals induced by self‐assembly of nucleating agent and its micropores formation during uniaxial stretching

The β-nucleated isotactic polypropylene (β-iPP) cast films containing networks of self-assembled nucleating agent (NA) was prepared under the specific processing field in this work. It was found that oriented β-transcrystals (β-TCs) formed by crystallizing on the needle-like agglomerates of self-assembled NAs. From the results, the microporous membranes with high porosity were obtained by uniaxial stretching the cast films consisted of β-TCs and the micropores morphology was analogous to that of the separation of row-nucleated lamellae. With the analysis of mechanism of pores formation, the oriented lamellae on β-TCs can play a similar role to the row-nucleated lamellae, presenting another possibility of crystalline morphology to prepare microporous membranes with uniaxial stretching. This work found another suitable crystalline morphology differed from row-nucleated lamellae, that is, β-TCs, to fabricate PP microporous membranes through uniaxial stretching. Moreover, it provided a great perspective to establish the relationship between the crystalline and final membranes performance, which helped us to conduct further research on the crystallographic structure of microporous membranes.