Comparative study on the crystallization behavior of β-isotactic polypropylene nucleated with different β-nucleation agents —effects of thermal conditions



In this study, the crystallization behavior of the β-isotactic polypropylene (β-iPP) samples nucleated by a rare earth based β-nucleating agent (β-NA) WBG-II and a metal salts compound β-NA NAB83 (denoted as WPP and NPP, respectively) under different cooling conditions were comparatively investigated. The thermal conditions such as the cooling rate, isothermal crystallization temperature, isothermal crystallization time, and the subsequent cooling to room temperature. The results of WAXD, SEM, and nonisothermal crystallization reveal that under the same processing conditions, the crystallite size of NPP is smaller, which arrange more compactly as compared with WPP. Meanwhile, NPP has shorter crystallization rate and higher β-nucleation selectivity, but WPP can crystallization at wider temperature range. The results of isothermal crystallization showed that NPP has higher selectivity and higher β-nucleation efficiency, which favors the formation of high proportion of β-phase at the isothermal crystallization temperature of 110–130°C with and without subsequent cooling; WPP has lower selectivity, which can only induce high content of β-phase under isothermal crystallization without subsequent cooling to 25°C. In tuning the crystallization behavior and the properties of β-PP, the joint influence of the efficiency and selectivity of the β-NA, and the thermal conditions should be taken into consideration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40115.