AbstractStudies are reported on melt rheological behavior of some binary and ternary blends of polypropylene (PP) with one or two of the following polymers: styrene–b‐ethylene butylene–b‐styrene triblock copolymer (SEBS), polystyrene (PS), and high‐density polyethylene (HDPE). Blend composition of the binary blends PP/Xor ternary blends PP/X/Ywere so chosen that the former represent addition of 10 wt Xto PP while the latter represent 10 wt addition ofXorYto the PP/Yor PP/Xblend of constant composition 90:10 by weight,X/Ybeing SEBS, PS, or HDPE. Measurements were made on a capillary rheometer using both temperature elevation and constant temperature methods to study the behaviors prior to flow and in the flow region. Flow behavior, measured at a constant temperature (200°C) and varying shear stress (from 1.0 to 5.0 × 106dyn/cm2) to evaluate melt viscosity and melt elasticity parameters, is discussed for its dependence on the nature of the blend. Extrudate distortion, studied as a function of shear stress to evaluate the critical shear stress for the onset of extrudate distortion, showed differences in the tendency for extrudate distortion or melt fracture of these different blends. Also discussed is the effect of melt viscosity and melt elasticity on extrudate distortion behavior at the critical condition, which showed a unique critical value of the ratio (melt elasticity parameter)1/2(melt viscosity) for all these blends. Blend morphologies before and after the flow through the capillary are investigated through scanning electron microscopy, and their correlations with rheological parameters of the melt ar
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