In situ generation of a self-dispersed beta-nucleating agent with increased nucleation efficiency in isotactic polypropylene

摘要

Addition of a beta-nucleating agent (beta-NA) is the most effective method of preparing beta-nucleated isotactic polypropylene (beta-iPP); however, the poor dispersion and agglomeration of beta-NAs limit nucleation efficiency. To solve this problem, a self-dispersing beta-NA strategy was developed based on in situ preparation of beta-NA (instead of pre-addition) during the processing of iPP. Zinc adipate (ZnAA), a typical beta-NA, was chosen; self-dispersed ZnAA (ZnAA(IS)) was prepared in situ from its reaction precursors adipic acid (AA) and zinc oxide (ZnO) during extrusion of iPP. In situ preparation of ZnAA(IS) led to a significantly higher nucleation efficiency than pre-addition of ZnAA. The beta-crystal content (k(beta) value) of nucleated iPP prepared with ZnAA(IS) reached 0.99, significantly higher than iPP prepared with ZnAA. Moreover, the impact strength of 0.1 wt % ZnAA(IS)/iPP composites was nearly 5.3-fold higher than neat iPP with a net gain in reinforcement (157%) compared to pre-addition of ZnAA. To explain these phenomena, we proposed mechanism for the self-dispersion of beta-NA in the context of in situ generation of beta-NA during iPP processing; the mechanism was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Polarized Optical Microscopy (POM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) data. Therefore, this strategy and method of preparing beta-NA in situ offers unique advantages that will advance the production and application of beta-iPP. Furthermore, this strategy could potentially be extended to solve issues of poor dispersion and agglomeration for other additives. (C) 2018 Elsevier Ltd. All rights reserved.