(30g) The Crystallization Behavior of Isotactic Polypropylene Induced By a Novel Anti-Nucleating Agent and Its Inhibition Mechanism of Nucleation

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 (T_cp)
and rate of iPP, generating remarkable anti-nucleation effects. The results of
differential scanning calorimetry (DSC) and polarized optical microscopy (POM) showed
T_cp 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

Graphical
abstract