Highly conducting poly(methyl methacrylate)/carbon nanotubes composites: Investigation on their thermal, dynamic-mechanical, electrical and dielectric properties

Nanocomposites of poly(methyl methacrylate) (PMMA) containing various multi-walled carbon nanotubes (MWCNT) contents were prepared using melt mixing. Several techniques were employed to study the influence of the MWCNT addition on the thermal, mechanical, electrical and dielectric properties of the PMMA matrix. The electrical percolation threshold (pc) was found to be 0.5 vol.% by performing AC and DC conductivity measurements. Significantly high conductivity levels (σdc) were achieved: σdc exceeds 10−2 S/cm already at 1.1 vol.%, the criterion for EMI shielding (σdc > 10−1 S/cm) is fulfilled at 2.9 vol.%, and the highest loaded sample (5.2 vol.%) gave a maximum value of 0.5 S/cm. Dielectric relaxation spectroscopy measurements in broad frequency (10−1−106 Hz) and temperature ranges (−150 to 170 °C) indicated weak polymer–filler interactions, in consistency with differential scanning calorimetry and dynamic-mechanical analysis findings. Weak polymer–filler interactions and absence of crystallinity facilitate the achievement of high conductivity levels in the nanocomposites.