Evidence of Percolated Network at the Linear - Nonlinear Transition in Oscillatory Shear

In this publication we review evidence for the detection of a percolated network in polymer nanocomposites at the linear - nonlinear transition in oscillatory shear tests. Two types of nanocomposites based on branched polymers as matrix are compared: a low density polyethylene (LDPE) and graphite nanoplatelets (GnP) as filler and a poly(ethylenebutyl acrylate) (EBA) containing graphite nanoplatelets and carbon black (CB). Oscillatory shear tests were analyzed in the framework of Fourier-transform rheology and Tschebyshev polynomial decomposition. For both nanocomposites, in the vicinity of the electrical percolation threshold, i.e. the formation of a continuous filler network, a distinct region is evidence at the transition linear - nonlinear transition in the strain dependent third relative higher harmonics of the shear stress Fourier spectra. The region can be characterized by different strain amplitude dependence that could be related to the specific filler morphologies, however, further investigations are required to assess the factors that influence the linear - nonlinear transition region in polymer nanocomposites.