Analysis of the electrical and rheological behavior of different processed CNF/PMMA nanocomposites

Carbon nanofiber (CNF)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via melt-compounding, solvent casting and in situ polymerization. Mechanical properties, rheological behavior and electrical resistivity were investigated in specimens with varying CNF loadings. The three processing techniques were compared. Improved properties were obtained in the solvent processed and in situ polymerized composites. The rheological and electrical percolation of these nanocomposites appeared in the same concentration set (between 1 and 5 wt%). No changes were found in melt-compounding, even by the addition of 10 wt% of CNFs. Electrical resistivity of the samples prepared by solvent casting was measured before and after pressing in the hot plate press. It is remarkable that in the non-pressed samples the CNFs formed an efficient 3-D conductive network, yielding composites with percolation thresholds even six orders of magnitude lower than after pressing, where this 3-D network was destroyed.