Studies on melt flow properties of low density and linear low density polyethylene blends in capillary extrusion

Abstract

Two linear low density polyethylenes (LLDPE) with a different melt flow index (MI) are selected to blend with a low density polyethylene (LDPE) in molten state by means of a screw extruder. The flow behaviour of the blend melts is studied by using capillary rheometry under rear practical processing conditions. The results indicate that with addition of the weight percentage content ( φ LD ) of LDPE the end pressure losses decrease for the blends with low MI LLDPE and increase for the blends with high MI LLDPE. These are similar to the case of apparent shear viscosity ( η a ) of the blend melts. The dependence of η a on temperature can be described by the Arrhenius equation. The relationship between η a and component viscosity accords with the logarithmic mixing rule, and the shear flow of the blend melts basically obeys the index law.