Linear Low-Density Polyethylene Nanocomposites by In Situ Polymerization Using a Zirconium-Nickel Tandem Catalyst System

A series of linear low-density polyethylene (LLDPE) nanocomposites containing different types of nanofiller (TiO2, MWCNT, expanded graphite, and boehmite) were prepared by in situ polymerization using a tandem catalyst system composed of {Tp(Ms)}NiCl (1) and Cp2ZrCl2 (2), and analyzed by differential scanning calorimetry, dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). Based on these analyses, the filler content varied from 1.30 to 1.80 wt %. The melting temperatures and degree of crystallinity of the LLDPE nanocomposites were comparable to those of neat LLDPE. The presence of MWCNT as well as boehmite nucleated the LLDPE crystallization, as indicated by the increased crystallization temperature. The DMA results showed that the presence of TiO2, EG, and CAM 9080 in the LLDPE matrix yielded nanocomposites with relatively inferior mechanical properties compared to neat LLDPE, suggesting heterogeneous distribution of these nanofillers into the polymer matrix and/or the formation of nanoparticle aggregates, which was confirmed by TEM. However, substantial improvement in the storage modulus was achieved by increasing the sonication time. The highest storage modulus was obtained using MWCNT (1.30 wt %). (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3506-3512