Isothermal Crystallization and Melting Behavior of Polypropylene with Lanthanum Complex of Cyclodextrin Derivative as a β-Nucleating Agent

A novel highly active beta-nucleating agent, beta-cyclodextrin complex with lanthanum (beta-CD-MAH-La), was introduced to isotactic polypropylene (iPP). Its influence on isothermal crystallization and melting behavior of iPP was investigated by differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), and polarized light microscopy (PLM). WAXD results demonstrated that beta-CDMAH- La was an effective beta-nucleating agent, with beta-crystal content of iPP being strongly influenced by the content of beta-CD-MAH-La and the isothermal crystallization temperature. The isothermal crystallization kinetics of pure iPP and iPP/beta-CD-MAH-La was described appropriately by Avrami equation, and results revealed that b-CD-MAH-La promoted heterogeneous nucleation and accelerated the crystallization of iPP. In addition, the equilibrium melting temperature (T-m(0)) of samples was determined using linear and nonlinear Hoffman-Weeks procedure. Finally, the Lauritzen-Hoffman secondary nucleation theory was applied to calculate the nucleation parameter (Kg) and the fold surface energy (re), the value of which verify that the addition of b-CD-MAH-La reduced the creation of new surface for b-crystal and then led to faster crystallization rate. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3651-3661, 2011