Rheology of metallocene catalyzed ethylene/α-olefin copolymers

摘要

The viscoelastic properties of ethylene/alpha-olefin copolymers (LLDPE) produced by the metallocene catalysts have been studied. Effects of long chain branchings and molecular weight distribution on rheological properties were investigated on four types of polymers produced using the different kinds of catalysts. The following conclusions were obtained through two types of polymers produced by CGC (Constrained-Geometric Catalyst) and mono-Cp (mono-Cyclopentadienyl) types. The effect of very long relaxation times based on the long chain branching of the sample obtained by CGC and mono-Cp type appeared in dynamic viscoelastic functions, creep recovery and elongational viscosity. The critical stress in shear flow property of the samples showed much lower stress compared with the polymer having no long chain branching. Especially, it was found that a long chain branching and a high molecular weight component cause strong effects on the steady state recoverable compliance and elongational viscosity from measuring creep recovery and elongation flow in LLDPE produced using mono-Cp catalyst.