Shear viscosity of rubber modified thermoplastics: Dynamically vulcanized thermoplastic elastomers and ABS resins at very low stress

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Abstract
The shear viscosity of PP‐EPDM dynamically vulcanized thermoplastic elastomers and ABS resins were investigated using (a) a constant shear stress creep instrument, (b) a rotational rheometer, and (c) a capillary extrusion rheometer. It was found that stresses exist for some of these materials below which they exhibit only finite deformations. This indicates they exhibit yield values. Much attention was given to measurements of creep at low stresses especially in the neighborhood of yield values. The magnitudes of the yield stresses obtained from these low stress measurements are significantly lower than those obtained using standard extrapolation to zero shear rate of higher stresses from rotational instruments. We also observed a high shear viscosity (∼109 PA s) plateau in the materials of high rubber content. We contrasted our results to those found in the literature.