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Melt Viscoelastic Behavior in Capillary Extrusion of Polypropylene/EPDM/Glass Bead Ternary Composites

The melt viscoelastic properties of polypropylene (PP)/ethylene-propylene-diene monomer copolymer (EPDM)/glass bead (GB) ternary composites were measured in a wide scope of shear rates by using a Rosand capillary rheometer, to indentify the effects of shear stress, particle content and its surface treatment on the melt viscoelastic behavior during extrusion of the composites. The apparent shear rates varied from 10 to 105 s— 1, and the test temperature was 190°C. The results showed that the entry pressure drop (ΔPen) and the melt extension viscosity (ηe) increased with an increase of shear stress (τw), and both the ΔPen and ηe were roughly an exponent function of τw respectively. The influence of the bead surface treatment on the ΔPen and η e is insignificant. The die-swell ratio (B) of the melts increased roughly linearly with an increases of τw, while decreased approximately nonlinearly with an addition of the GB volume fraction. The values of B of the composite system for the EPDM grafted with maleic anhydride were somewhat more than those of the other composite systems under the same test conditions, especially at lower glass bead concentration.