Evolution of Phase Morphology, Rheology, and Electrical Conductivity of PA6/POE Blends Containing Graphene during Annealing under SAOS

Abstract

The evolution of rheological response, phase morphology, and electrical properties of PA6/POE blends (80/20) with graphene primarily localized inside the POE minor phase and at the interface are investigated during annealing under small-amplitude oscillatory shear (SAOS). Analysis of the dynamic viscoelastic response of these nanocomposites revealed that it is primarily governed by the graphene 3-dimensional structure, which evolves during the rheological measurement. Comparing isochronal frequency sweeps with frequency sweeps close to the equilibrium condition illustrates that graphene content and the evolution of its 3D structure have the same impact on rheological and electrical properties. Interestingly, regardless of different blend morphology, the linear and nonlinear viscoelastic behavior follow the fractal scaling theory indicating that the 3-dimensional graphene structure is self-similar. With increasing graphene content, the phase morphology changes from typical droplet-matrix morphology to droplet clusters and cocontinuous morphology. The stability of the blend morphology when annealing under SAOS (0.1 rad/s) depends on the balance between the rate of coalescence and shape relaxation. Interestingly, our morphological observation for nanocomposites containing 0.5% and 1% of graphene shows that while the presence of graphene slows down the shape relaxation, it increases the coalescence rate within the first 30 min of annealing as compared to the neat blend. The increased coalescence rate comes from the compressive deformation applied during sample loading along with a slow shape relaxation and graphene bridging between neighboring domains.

PEG-Grafted Graphene/PLLA Nanocomposites: Effect of PEG Chain Length on Crystallization Kinetics of PLLA

“…All of the composites presented a typical Newtonian behavior over a wide range of frequency and a slight shear-thinning behavior at high frequencies except when GO-g-PEG10000 in concentrations of 1 and 1.5 wt % was added to PLLA. In this case, a yield stress was observed at low frequencies, indicating that GO-g-PEG10000 nanoparticles start to form a network 37 at these concentrations, which are in good agreement with the results of OM images, as shown in Figure 5 e.…”