Study on variable nucleation efficiency of N,N ′-Dicyclohexyl-2,6-naphthalenedicarboxamide on isotactic polypropylene

Abstract

N, N′-Dicyclohexyl-2,6-naphthalenedicarboxamide (NU100), a commercial β-nucleating agent (NA) for isotactic polypropylene (iPP), is found dissolvable in iPP melt. Various heating temperatures ( Ths) of iPP/NU100 cause different solubilities of NA, resulting in various aggregation morphologies of NU100 in the melt. Moreover, nucleation efficiency of NA NU100 on iPP changes with the Th of iPP/NU100. In this article, the effects of Th on nucleation behaviors of iPP nucleated with different concentrations of NU100 were systematically studied. The results indicated nucleation efficiency of NU100 depended not only on concentration of NA but also on Th of nucleated iPP. With the increase of Th, crystallization peak temperature ( Tcp) of nucleated iPP decreased remarkably. The whole process that Tcp shifted from 126.8°C to 120.8°C was obtained by investigating the nucleation behavior of iPP/0.1 wt% NU100. Polarized optical microscopy observation confirmed lower Tcp, representing the crystallization of iPP nucleated by dissolved–recrystallized NA NU100. Further, diverse aggregation morphologies of NA in iPP melt during crystallization were observed. A schematic diagram was proposed illustrating the morphologies formed during recrystallization process of NU100 melted at different Ths.