Melt Rheology of LDPE and Glass Bead Filled LDPE Composite

Abstract

The effects of shear rates and temperatures on the melt shear viscosity (17w) and the relationship between the first normal stress difference (NI) and the wall shear stress (Tr,,) of low density polyethylene (LDPE) and glass bead filled LDPE composite, over a temperature range from 130 to 1 70'C and shear rates varied from 100 to I 10 S-l, have been investigated by employing a capillary rheometer. With a rise of temperatures and increasing shear rates the melt viscosity decreases nonlinearly. The melt flow obeys the power law and the power law index increases with a rise of temperature. N₁ is approximately an exponential function of rw. The dependence of qw on temperatures basically accords with the Arrhenius expression. Under the same test conditions, the qw and N₁ of the composite melt are somewhat lower than those of the pure LDPE melt. On the basis of the predecessors' work, an equation describing the relationship between N₁ and pressure drop has been presented in this article. Good agreement is shown between the predicted N₁ values and the measured data from the melts.