Viscoelastic properties and melt rheology of novel polyamide 6/fluoroelastomer nanostructured thermoplastic vulcanizates

Abstract

The present article reports viscoelastic properties and melt rheology of novel nanostructured thermoplastic vulcanizates (TPVs) consisting of dispersed nanodimensional fluoroelastomer (FKM) particles into the continuous polyamide (PA6) matrix. The influence of dynamic vulcanization on the above properties of the blends was reported. The storage modulus and loss modulus were plotted against reduced frequency to understand the behavior of nanostructured TPVs. PA6/FKM TPVs showed pseudoplasticity and obeyed cross viscosity model. Insight into how the crosslink density of TPVs affects the rheological response was discussed. Also, a new relationship of zero shear viscosity (η 0) with the crosslink density of TPVs was proposed to gain insight into dynamic vulcanization. It was found that up to a certain amount of curative concentration, η 0 depends upon the crosslink density to a power equal to 3.4 and is roughly proportional to the crosslink density on further increase of curative concentration. van Gurp–Palmen plot of phase angle versus reduced complex modulus indicated the droplet–matrix morphology of the PA6/FKM blends which was further confirmed from field emission scanning electron microscopy and atomic force microscopy studies, where FKM nanoparticles (60–80 nm) were the dispersed phase. Various melt elastic properties of TPVs such as die swell, first normal stress difference, recoverable shear strain, and apparent elasticity were measured and analyzed. TPV extrudates were examined using surface finish and roughness values. TPVs exhibited smoother extrudate surface than reported earlier. Extrudate surface roughness from atomic force microscopy was used to analyze the processing behavior of TPVs.