Conductive network formation and its dynamic process for multiwalled carbon nanotubes (MWNTs) and carboxyl-tethered MWNT (MWNT-COOH) filled poly(vinylidene fluoride)(PVDF) systems were investigated. Based on real-time tracing the variation of electrical resistivity of systems with isothermal treatment time, the conductive network formation was evaluated. It was found that the conductive network formation was temperature and time dependent. The percolation time, characterized at a certain annealing time where the electrical resistivity started to decrease drastically, decreased with the increase of the filler concentration or the annealing temperature. However, the values of the percolation time and the activation energy of conductive network formation for the PVDF/MWNT-COOH system were higher than those of the PVDF/MWNT system, indicating that the interaction between MWNTs and PVDF molecules played an important role in the conductive network formation of the composites. Furthermore, a modified thermodynamic percolation model was proposed to predict the percolation time of PVDF/MWNT composites. It was found that the calculated results fit the experimental data very well. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 1405-1411, 2009