Multiwalled carbon nanotubes (MWCNTs)/carbon black (CB) mixed filler filled polyoxymethylene (POM) composites were prepared by melt mixing in a rotational rheometer.The relationship between electrical resistivity of the composites and the filler concentration was investigated.The electrical percolation threshold of MWCNTs/CB mixed filler-filled POM is much lower than that of CB-filled POM but higher than MWCNTs-filled POM

because MWCNTs and CB build up the conductive path together.The experimental data were used to examine the existing equation derived from the model of mixed filler systems which was published previously

and the comparison showed that deviation existed for some data points.It is speculated that the conditions for using the model are too ideal

not suitable to practical cases

so deviation is inevitable.In order to facilitate the practical application

the equation was further developed

and a new equation describing the relationship between percolation threshold and the ratio of the two fillers was obtained.A working curve was drawn on the basis of the newly developed equation and examined by the experimented data.The results demonstrate that the working curve can provide a general guidance for practice.This work shows that the existing model of mixed carbon filler systems is useful for predicting the conductive behavior of the composite materials.