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 (gamma(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 gamma(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 gamma(c) < 6.3% (linear viscoelastic regime), while the values decreased above gamma(c) due to the destruction of the system's morphology.

Automated summary

The study found that the addition of multiwall carbon nanotubes in a co-continuous immiscible polymer blend can significantly decrease electrical resistivity through oscillatory shearing, but can also increase resistivity under large deformation due to the destruction of MWCNT paths.