Abstract

In this work, polyethylene and poly-ethylene-co-α-olefins were synthesized by mean of modified Ziegler-Natta catalysts. The support used to prepare the catalysts and the catalyst itself were subject of ultrasound wave in order to avoid material aggregation and to assets its effect on catalytic activity. The catalysts obtained were characterized by standard spectroscopic techniques. Titanium content in catalysts, as determined by FRX spectroscopy, ranges between 3 and 13 % wt/wt, while titanium concentration in the slurry, as determined by UV-VIS spectroscopy, ranges between 0.008 and 0.0551 mmol Ti/mL. Catalysts were evaluated towards ethylene polymerization and ethylene-α-olefins (1-hexadecene, 1-decene, 1-octene, 1-hexene) co-polymerization. The catalytic tests were carried out at different times of "maturation" tIC (time of injection of the comonomer). The highest activity was found with tIC = 5 min in all cases. The catalytic activity varies in the order 1-hexadecene> 1-decene> 1-octene> 1-hexene. A synergistic effect or positive comonomer effect was observed when 1-hexadecene or 1-decene co-monomers where added. Activity for 1-hexadecene/ethylene copolymerization was nine (9) times higher than the activity found for ethylene polymerization. An opposite effect in catalytic activity or negative comonomer effect where found when α-olefins with shorter chain lengths where used. Incorporation of the α-olefins into the polyethylene chains resulted in a sharply decrease of the melting temperatures, density and crystallinity of the copolymers.