Comparison of the predictions of viscoelastic and plastic-viscoelastic fluid model to the rheological behaviour of polystyrene and polystyrene-carbon black compounds

Abstract

The rheological properties of a polystyrene melt and its compounds with carbon black are compared with a non-linear viscoelastic fluid theory and a plastic-viscoelastic fluid model. Shear viscosities, principal normal stresses and elongational viscosities are investigated for melt and compound. The relaxation spectra for the melt was determined with an eccentric disc rheometer. The Bogue-White model gave satisfactory agreement for the melt with an “a” parameter of 0.5. For the plastic-viscoelastic fluid theory, a Bogue-White model was used to represent theH functional. Theτi and “a” parameters were taken to be the same as for the pure melt while theGi were increased by a hydrodynamic factor. A yield value was obtained from the compound data. Generally good agreement was found but some discrepancy exists for the elongational flow experiments.