Rheology–morphology interrelationship in high-density polyethylene/polyamide-6 microfibrillar composites

Abstract

Due to the importance of rheology and morphology of microfibrillar reinforced composites (MFCs), a study has been conducted on MFCs based on high-density polyethylene (HDPE) and polyamide-6 (PA-6) using scanning electron microscope and dynamic rheometer. In the absence of an interfacial modifier and at 10 wt% concentration of the dispersed phase (PA-6), two principal factors, elongational deformation and coalescence, were found to be controlled by viscosity and elasticity ratios of the pure constituents accounting for the observed morphology of MFCs. The developed microfibrillar morphology remarkably influenced the viscoelastic properties of MFCs. It was observed that when the viscosity ratio approached unity and the elasticity ratio was minimal, the extent of coalescence in composite was significant. The rheological assessment showed enhanced storage modulus and complex viscosity upon microfibrils formation. This was more pronounced for samples with thinner microfibrils due to more strongly entangled network, compared to the composites with thicker microfibrils. The length-to-diameter ratio of the microfibrils could not be estimated due to their highly asymmetric length scale.