SYNTHESIS AND CHARACTERIZATION OF POLYETHYLENES OBTAINED FROM ZIEGLER-NATTA (ZN) CATALYSTS BASED ON MONO AND BIMETALLIC SPECIES SUPPORTED IN A TYPE ADDITIVE MgCl2/SiCl4-n(OHEx)n.

Abstract

In this work, Ziegler-Natta (ZN) catalysts based on species supported in an adduct of the type MgCl2/SiCl4-n(OHex)n to polymerize ethylene were evaluated. Also, the polyethylenes obtained with mono and bimetallic systems were characterized by Differential Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal properties of the PE (Tm between 131-136 °C and (1-λ) between 58-64%) were found in the range for high density polyethylenes. The TGA results showed that the polyethylenes derived from the catalysts TiCl4 and (TiCl4)x-(VCl3) begin their degradation at higher ranges than the polyethylene synthesized with the catalyst (TiCl4)x-(CrCl3), indicating that the presence of chromium in the latter gave it lower thermal stability. A sponge-like morphology was observed in the polyethylene obtained with the TiCl4/MgCl2/SiCl4-n(OHex)n catalyst system, which varied by adding another metal center (Cr and V) to a globular type morphology (bunch of grapes). In the micrographs of the polyethylenes obtained by TEM, the lamellar town were observed decreasing in the following order: PETi (11,7 a 23,3 nm) < PETi/V (8,3 a 16,7 nm) < PETi/Cr (5,0 a 16,7 nm).