STUDIES ON MELT FLOW PROPERTIES OF LOW-DENSITY AND LINEAR LOW-DENSITYPOLYETHYLENE BLENDS IN CAPILLARY EXTRUSION

Two linear low density polyethylenes (LLDPE) with a different melt flo w index (MI) are selected to blend with a low density polyethylene (LD PE) in molten state by means of a screw extruder. The flow behaviour o f the blend melts is studied by using capillary rheometry under rear p ractical processing conditions. The results indicate that with additio n of the weight percentage content (phi(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 s hear viscosity (eta(a)) of the blend melts. The dependence of eta(a) o n temperature can be described by the Arrhenius equation. The relation ship between eta(a) and component viscosity accords with the logarithm ic mixing rule, and the shear flow of the blend melts basically obeys the index law. (C) 1997 Elsevier Science Ltd.