Correlations between the characteristic rheological quantities and molecular structure of long-chain branched metallocene catalyzed polyethylenes

Different rheological quantities, such as the zero shear-rate viscosity η₀ and the linear steady-state elastic compliance J _e⁰ of long-chain branched metallocene-catalyzed ethene homopolymers and ethene-/α-olefin copolymers with a polydispersity M _w/M_n≈ 2, were correlated with the molar mass M _w and degree of long-chain branching λ. A linear reference for the δ(|G^*|) plot was used to show the effect of long-chain branches on this rheological property. The linear steady-state elastic compliance J_e⁰ correlated with the zero shear-rate viscosity increase factor η₀/η₀^lin and the characteristic phase angle δ_c. However, the latter only works when compensating for the influence of the molar mass on J _e⁰ by the relationship between J_e⁰ and M_w established elsewhere (Stadler and Münstedt, JoR, 2008). The characteristic phase angle δ_c and zero shear-rate viscosity enhancement factor η₀/η₀^lin are linked to each other by the linear dependencies for the type I and type II viscosity functions.