Study of the influence of the reaction parameters on the composition of the metallocene‐catalyzed ethylene copolymers using temperature rising elution fractionation and 13C nuclear magnetic resonance

Abstract

AbstractPolyethylene copolymers prepared using the metallocene catalyst rac‐Et[Ind]2ZrCl2 were fractionated by preparative Temperature Rising Elution Fractionation (p‐TREF) and characterized by 13C nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) to study the heterogeneity caused by experimental conditions. Two ethylene–1‐hexene copolymers with different 1‐hexene content and an ethylene–1‐octene copolymer all obtained using low (1.6 bar) ethylene pressure were compared with two ethylene–1‐hexene copolymers with different 1‐hexene content obtained at high ethylene pressure (7.0 bar). Samples obtained at low ethylene pressure and with low 1‐hexene concentration in the reactor presented narrow distributions in composition. Samples prepared with high comonomer concentration in the reactor or with high ethylene pressure showed an heterogeneous composition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 155–163, 2002; DOI 10.1002/app.10284