Evolution of the electrical resistivity at rest and during oscillatory shearing of co-continuous morphology (PP/PMMA)/MWCNT systems

In this work, a modified parallel-disks configuration on a strain-controlled ARES rheometer (TA Instrument) was used to study the evolution of the electrical resistivity at rest and during oscillatory shearing of a co-continuous immiscible polymer blend morphology based on polypropylene and /polymethyl(methacrylate) (PP/PMMA) in which various amounts (0–3 wt%) of multiwall carbon nanotubes (MWCNT) were added. The co-continuity of both PP and PMMA phases allowed the buildup of a conductive network due to the preferential localization of the conductive MWCNT at the interface between PP and PMMA. Under a stepwise increase of the oscillatory strain amplitude below a critical value (γ_c = 6.3%), a significant decrease in the electrical resistivity was observed for MWCNT concentrations above the percolation threshold (0.3 wt%) due to the conductive paths induced by both thermal (Brownian) motion and oscillatory shearing. However, for deformation amplitudes higher than γ_c, the resistivity increased due to the destruction of the MWCNT paths induced by the large deformation imposed on the PP/PMMA interface. These observations were also confirmed by the evolution of the storage modulus (G′) which remained constant for γ_c < 6.3% (linear viscoelastic regime), while the values decreased above γ_c due to the destruction of the system's morphology.