Isothermal crystallization and melting behavior of polypropylene with lanthanum complex of cyclodextrin derivative as a β-nucleating agent



A novel highly active β-nucleating agent, β-cyclodextrin complex with lanthanum (β-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 β-CD-MAH-La was an effective β-nucleating agent, with β-crystal content of iPP being strongly influenced by the content of β-CD-MAH-La and the isothermal crystallization temperature. The isothermal crystallization kinetics of pure iPP and iPP/β-CD-MAH-La was described appropriately by Avrami equation, and results revealed that β-CD-MAH-La promoted heterogeneous nucleation and accelerated the crystallization of iPP. In addition, the equilibrium melting temperature (Tmath formula) 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 (σe), the value of which verify that the addition of β-CD-MAH-La reduced the creation of new surface for β-crystal and then led to faster crystallization rate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011