Synthesis, structure, and thermal properties of new polypropylene nanocomposites prepared by using MgCl2-mica/TiCl4 based catalyst

摘要

Preparation of polypropylene/mica nanocomposites via in situ polymerization is investigated. The nanocomposites were successfully synthesized using a Ziegler-Natta catalyst based on MgCl2/modified mica/TiCl4. Muscovite mica was organically modified with quaternary ammonium salt, and with triethylaluminum. The treatment with triethylaluminum increased the disorder in the stacking of clay layers, producing a more active catalyst for propylene polymerization, although the mica containing catalysts had lower activity than the standard one prepared without clay. The nanostructure of the composites was characterized by X-ray diffraction. The results showed that part of the mica layers were exfoliated in the polymer matrix, although tactoids were still present. Small-angle X-ray scattering analysis was used to determine how mica and its concentration influence the size of the polymer nanocrystals. Differential scanning calorimetry was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the nanocomposite samples. Thermogravimetric analysis showed that polypropylene/mica nanocomposites presented much higher thermal stability than the polypropylene without mica, which means that mica had a barrier effect against heat. (C) 2017 Wiley Periodicals, Inc.