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

Abstract

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 (ΔP_en) and the melt extension viscosity (η_e) increased with an increase of shear stress (τ_w), and both the ΔP_en and η_e were roughly an exponent function of τ_w respectively. The influence of the bead surface treatment on the ΔP_en and η_e is insignificant. The die-swell ratio (B) of the melts increased roughly linearly with an increases of τ_w, 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.

Keywords

polypropylene EPDM glass bead composite extrusion flow viscoelastic property.

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