Non-Linear Rheology of Polymer Melts

In order to study non-linear viscoelasticity behavior polymer blends in shear flow, the experiments of steady shear, start up steady shear and step strain are necessary. Using suitable constitutive equations one can allows understanding nonlinearity phenomena and then comparing results to experimental data. In most of polymer processing, such as injection molding and extrusion, polymer melts are subjected to high deformations. To study nonlinear viscoelastic properties, it is necessary to have a rheometer to generate high shear rates. A sliding parallel plate rheometer incorporating a shear stress transducer has been developed. This rheometer has been equipped with a robust servohydraulic linear actuator which can generate shear rates and frequencies up to 900 (1/S) and 500 (Hz) respectively, compared with maximum 500 (1/S) and 100 (Hz), used in the latest rheometers. Using this system, one can generate different strain histories such as small amplitude oscillatory strain, large amplitude oscillatory strain, step strain, multistep strain and sequential strain.