Measurement of Flow Characteristics of Molten Polymer Blends

Abstract

Viscosity and normal stress difference of polymer blends such as polyethylene (PE) -polypropylene (PP) and polyethylene (PE) -polystyrene (PS) systems were measured and the morphology of extruded samples was observed with the electron microscope.
Fraction dependency of viscosity was the same as shown by the result of the previous work. In the measurement of normal stress differences with the flow birefringence method, only the first normal stress difference was obtained and it was found that normal stress differences of these blends were smaller than those of the pure components over most fractions.
Power law was used to study shear rate dependencies of viscosity and normal stress difference. A great change in the power law exponents of these flow characteristics occurred at a PE fraction of 0.6. It was concluded that the flow mechanism changes near that fraction. The stress-optical coefficient necessary for the flow birefringence method was experimentally measured and its tendency was found to be the same as those predicted by the theory of rubber elasticity. The morphology observed with electron micrograph suggested some information on microscopic flow behavior.