Rheological behavior of metallocene catalyzed PE and LDPE blends

The rheological behavior was studied for blends of metallocene catalyzed ethylene/1-butene copolymer(mPE) and low density polyethylene(LDPE). Steady-state viscosity and dynamic viscoelasticity were measured by using a DSR-200 rheometer with parallel plate geometry. Non-linear fitting with the modified cross model was conducted successfully. Due to lower molecular weight and narrower molecular weight distribution ((M) over bar (w)/(M) over bar (n) = 2.1), mPE has a lower sensitivity to shear, shown by a lower zero shear viscosity, higher values of shear rate and shear stress at the transition from Newtonian to non-Newtonian behavior, higher viscosities in shear rate range from 10(0) s(-1) to 10(2) s(-1). Zero shear viscosities of mPE/LDPE 50/50 and 25/75 (mass ratio) blends have a large positive deviation from log-additivity rule, due to a decrease of the free volume fraction in these blends, The transition stress and non-Newtonian index decrease with increasing LDPE fraction in blends, which indicate that the blends have high sensitivity to shear and improved processability, The single correlation between G' and G " corresponds to the behavior expected for a miscible blend.