The Arrhenius equation can be used to calculate the activation energy (Ea) of conductive network formation in a polymer melt [16], [17] and [18]. Essentially, the contact process between two conductive particles can be equivalent to the excluding process of polymer molecules between two particles [19]. Thus, the mobility of CNTs in the matrix can reflect the interaction of the polymer layer between CNT particles. In the present case, the Arrhenius equation can be expressed as
equation(2)
ln(tp)=lnA-Ea/RT
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where Ea is the activation energy, R is the gas constant, and T is the absolute temperature. Fig. 3a and b presents the Arrhenius plots of tp versus the inverse of the annealing temperature for CNT/EVA10 and CNT/EVA25 composites, respectively. A family of parallel linear relationship is observed for various CNT loadings. From the slope of the lines in Fig. 3a, the value of Ea is calculated to be constantly about 93.9 kJ/mol for CNT/EVA10 system, which is much lower than that (104.7 kJ/mol) for CNT/EVA25. This can be understood on the basis of the kinetic difficulty of the conductive network formation due to the stronger interaction and higher viscosity in EVA25 matrix. A similar result was also reported by Wu et al. [19], who found the oxidation condition on carbon black (CB) caused the increase of Ea in the CB/poly(methyl methacrylate) system.