The relationship between rheological behavior and microstructure of nanocomposite based on PA6/NBR/clay

Abstract

Microstructure, rheological properties and their relationships of PA6/NBR/nano‐clay nanocomposite have been investigated. Scanning electron microscopy (SEM) and transmission electron microscopy imaging techniques were used to study micro‐structure. The nano‐clay dispersion was measured by small angle X‐ray diffraction. Frequency sweep, steady shear, startup shear transient, and startup shear free transient experiments were carried out to study rheological characteristics of nanocomposite. SEM micrograph revealed that nano‐clay decreased the size of rubber droplets to a half in comparison with samples without nano‐clay. Storage modulus of nanocomposite containing 7% wt nano‐clay exhibited frequency independent behavior because of physical network which formed in matrix, in contrast to pure PA6 which showed terminal storage modulus at low frequencies. Shear thinning at high shear rates was observed by addition of rubber to PA6 matrix caused by deformation of rubber droplets. Nano‐clay orientation in shear flow field accelerated non‐Newtonian behavior in steady shear experiment. Transient shear viscosity studies were used for measurement the strength of nano‐clay physical network. It was found that network breakdown is more stress consuming factor in comparison with nano‐particle orientation and hydrodynamic forces. Elongation transient viscosity studies showed that critical Hencky strain for linear–nonlinear viscoelastic transition shifted to higher strains by increasing nano‐clay concentration. POLYM. COMPOS., 39:2403–2410, 2018. © 2016 Society of Plastics Engineers