Self-assembly and conductive network formation of vapor-grown carbon fiber in a poly(vinylidene fluoride) melt

The construction of vapor-grown carbon fiber (VGCF) conductive networks through the self-assembly process in a poly(vinylidene fluoride) (PVDF) melt was investigated. Depending on real-time tracing of the variation of electrical resistivity with isothermal treatment time, the properties and possible assembly mechanism of PVDF/VGCF composites were evaluated. It was found that the self-assembly velocity of VGCFs in the matrix increased with annealing temperature. Scanning electron microscopy showed that the coagulation of VGCFs formed the conductive paths in the matrix after annealing. The value for the activation energy of conductive network formation was about 144 kJ/mol, which was higher than the value for the activation energy of zero-shear-rate viscosity (η0∗) of the pure polymer (62 kJ/mol), but was close to the value for the activation energy of η0∗ of VGCF filled PVDF composites (135 kJ/mol). These results indicated that the conductive network of the composites was related to the interaction between PVDF molecules and VGCFs. According to a thermodynamic percolation model, a self-assembly velocity model for conductive network formation was proposed, and the result indicated that self-assembly velocity was a function of annealing time and temperature.