Filler dispersion and electrical properties of polyamide 12/MWCNT-nanocomposites produced in reactive extrusion via anionic ring-opening polymerization

The reactive extrusion of lauryl lactam to polyamide 12 (PA12) of controlled molar mass was successfully performed in a microcompounder. The maximum residual monomer content was less than 1%. The in-situ polymerization in the presence of 1–5 wt.% multiwalled carbon nanotubes (MWCNTs) was studied and the processing conditions were optimized with respect to the electrical resistivity and MWCNT dispersion. Runs which yielded in higher molar mass PA12 resulted in better dispersion of MWCNTs, whereas nanocomposites with lower molar mass PA12 had lower electrical percolation thresholds (MWCNT concentration ∼1 wt.%). A high screw speed of 200 rpm was identified to cause best dispersion and the lowest percolation threshold.