POLYETHYLENE-CLAY NANOCOMPOSITES WITH METALLOCENE CATALYST SUPPORTED ON BRAZILIAN BENTONITE

摘要

Polyethylene-clay nanocomposites have been prepared using in situ polymerization. In this study we have evaluated two minerals, silica and bentonite (smectite), as catalyst carriers for the polymerization of ethylene with commercially available zirconocene. The activities of the homogeneous and supported metallocene systems were also compared. We have observed that at high temperatures, ethylene consumption sharply decreases with time by employing homogeneous catalyst. Also, the polymerization profiles for both supported systems have rapidly achieved a steady state. Moreover, the performance of the smectite-supported system was very similar to that of the silica-supported catalyst. The obtained polymers were characterized according to their melting temperature (T_m) and crystallinity degree (X_c), through DSC analysis. The polyethylene melting temperature has significantly increased with the use of both supported systems in comparison with the homogeneous counterpart. The highest T_m of the obtained polyethylenes was 136.8°C, which corresponds to that synthesized by the smectite-supported catalyst.