2015 AIChE Annual Meeting
The crystallization behavior of isotactic polypropylene induced by a novel anti-nucleating agent and its inhibition mechanism of nucleation
Shicheng Zhao, Xin Yu, Hanzhang Gong, Zhong Xin*
Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, State-Key Laboratory of Chemical Engineering, Department of Production Engineering, East China University of Science and Technology, Shanghai, 200237, People's Republic of China
Abstract: The addition of foreign substances is well known to be able to improve the crystallization of iPP following a nucleation-promoting mechanism. In the present work, however, we found that zinc salt of 1, 4, 5, 6, 7, 7-hexachlorobicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid (HCHD-Zn) unexpectedly decreased the crystallization temperature (Tcp) and rate of iPP, generating remarkable anti-nucleation effects. The results of differential scanning calorimetry (DSC) and polarized optical microscopy (POM) showed Tcp of iPP decreased more than 4 oC and nucleation densities of iPP decreased nearly 70% upon the addition of the "anti-nucleating agent" HCHD-Zn. Isothermal crystallization kinetics indicated HCHD-Zn lowered the crystallization kinetic constant k of iPP but had similar Avrami exponent n value with neat iPP, which revealed HCHD-Zn hindered the crystallization of iPP but did not change the type of nucleation and growth of iPP. We propose a mechanism of anti-nucleation of iPP upon the addition of HCHD-Zn from a structural perspective. The removal of hydrochloride left a 3D network of iPP chains cross-linked by HCHD-Zn particles. Therefore, the restricted movement of polymer chains inhibited the nucleation of iPP.
Key words: Polypropylene, Anti-nucleating agent, Crystallization behavior, Inhibition mechanism