Retraction Note to: Effect of dynamic cross-linking on melt rheological properties of isotactic polypropylene (iPP)/ethylene–propylene diene rubber (EPDM)/nitrile rubber (NBR) elastomeric blends

Abstract

An attempt has been made to study the melt rheological properties of uncross-linked and dynamically cross-linked isotactic polypropylene (iPP)/ethylene-propylene-diene rubber (EPDM)/Nitrile rubber (NBR) elastomeric blends, at blending ratios 10–40 wt.%, EPDM/NBR are reported. Blends were prepared by melt blending in an internal mixture at 190 °C and various rheological parameters have been evaluated at 220 °C by single screw capillary rheometer. Cross-linking was performed with resole type dimethylol phenolic resin. The effects of (i) blends composition (ii) shear stress/shear rate on melt viscosity (iii) flow characteristics and shear sensitivity at processing (iv) melt elasticity of the extrudate and (v) dynamic vulcanization effect on the processing characteristics were studied. It was found that the melt viscosity increases with the increasing EPDM/NBR concentration and decrease with increasing intensity of the shear mixing of all the blend compositions. As compared to the uncross-linked blends, dynamically cross-linked blends displayed high pseudoplastic behavior and provides unique processing characteristics that enable to perform well in both injection molding and extrusion process. The high viscosity at low shear rate provides the integrity of the extrudate during extrusion, and the low viscosity at high shear rate enabling low injection pressure and less injection time. Also the low die-swell characteristics of cross-linked blends also gave high precision for dimensional control during processing (extrusion).