Dielectric rheological measurements of molten polymers

Rheological characterization of polymers above their melting points is performed with dielectric spectroscopy. A new in‐line interdigitated dielectric sensor as well as a commercial off‐line sensor were used to make the measurements. The dielectric dissipation or loss factor of a molten polymer was found to be directly proportional to independently measured rheological properties of the polymer. Time‐temperature superposition was used to translate dielectric and rheological curves to master curves where the curves are comparable in form, but the activation energy of a dielectrically‐induced relaxation was found to be lower than a rheological translational motion. The more localized and homogeneous effects imparted to the polymer during the dielectric measurement may cause the polymer to undergo a viscoelastic transition at a lower energy than the flow‐induced transition in rheological measurements. The dielectric methods detailed herein provide a new noninvasive technique to measure the viscoelastic properties of molten polymers.