Thermal and rheological properties of polyethylene blends with bimodal molecular weight distribution

摘要

Polyethylene blends with bimodal molecular weight distribution were prepared by blending a high molecular weight polyethylene and a low molecular weight polyethylene in different ratios in xylene solution. The blends and their components were characterized by the high temperature gel permeation chromatograph (GPC), different scanning calorimetry (DSC), and small amplitude oscillatory shear experiments. The results showed that the dependence of zero-shear viscosity (η_0) on molecular weight followed a power law equation with an exponent of 3.3. The correlations between characteristic frequency (ω_0) and polydispersity index, and between dynamic cross-point (G_x) and polydispersity index were established. The complex viscosity (η*) at different frequencies followed the log-additivity rule, and the Han-plots were independent of component and temperature, which indicated that the HMW/LMW blends were miscible in the melt state. Moreover, the thermal properties were very similar to a single component system, suggesting that the blends were miscible in the crystalline state.