Effect of nucleating agent supported on zeolite via the impregnation on the crystallization ability of isotactic polypropylene and its mechanism

Abstract

Addition of an α‐nucleating agent is the simple and effective method to increase nucleation efficiency of isotactic polypropylene (iPP). However, severe agglomeration and poor dispersibility of sodium 2,2′‐methylene‐bis(4,6‐di‐tertbutylphenyl) phosphate (NA11) decrease the nucleation efficiency in the iPP, and much more nucleating agent is needed to maintain the nucleating property. As a result, it becomes the key how to decrease the size of NA11 and increase the nucleating property. In this paper, zeolite 4A (Z4A) was firstly supported by NA11 through solution impregnation, and NA11 was dispersed by Z4A depending on the dispersion of zeolite as carrier for the second component. Then, the dispersed NA11 system (NA11‐Z4A) exhibited a superior nucleation behavior during the crystallization of the iPP matrix when it was used with iPP together. The isothermal and nonisothermal crystallization kinetics indicated that the NA11‐Z4A/iPP system had the best crystallization effect. Polarized optical microscopy (POM) and scanning electron microscopy (SEM) analyses showed that the size of NA11 decreased obviously when it was adsorbed on the surface of Z4A, which leads a better dispersibility of the nucleating agent and thus an accelerated nucleation process in the iPP matrix. In the end, the mechanism for the excellent dispersibility of NA11‐Z4A, which was based on hydrogen bonding between NA11 and Z4A, was confirmed by Fourier‐transform infrared spectroscopy (FTIR). Based on the research work, the solution impregnation strategy can potentially be applied to other systems to inhibit the agglomeration and improve the dispersibility of additives in iPP.