Electrical and dynamic mechanical behavior of BaTiO3/VGCF/LDPE composite

The electrical and dynamic mechanical behavior of barium titanate (BaTiO3)/ vapor-grown carbon fiber (VGCF)/Low Density Polyethylene (LDPE) composites has been studied. The measurement of electrical conductivity exhibits a low er percolation threshold and a more distinct two-stage percolation region, especially with a wide plateau between the two stages, for BaTiO3/VGCF/LDPE composites compared to the two-component system of VGCF/LDPE. This can be attributed to increase of the effective concentration of VGCF and the obstr uction of BaTiO3 particles on VGCF networks. The dynamic mechanical spectra of BaTiO3 /VGCF/LDPE composites present a distinctive ct relaxation region with its peak value nearly remaining constant at its high temperature side in contrast to the abrupt decrease of LDPE. Moreover, the loss factor in t he alpha relaxation region reaches its largest value for the composite of 8 vol% VGCF content. This means that the piezo-damping effect really functio ns in BaTiO3/VGCF/LDPE composites and only in certain conditions can this e ffect have practical significance. Further examination of the damping behav ior in a different relaxation region demonstrates that the piezo-damping ef fect is directly related to the relaxation behavior of the polymeric matrix . Also, the piezo-damping effect is highly temperature and frequency depend ent. The dielectric measurements suggest that, before the formation of a ce rtain critical conducting state, the energy dissipation approach of the pie zo-damping effect may be mainly determined by the interfacial polarization effect in the composite. Thus, it may be inferred that the piezo-damping ef fect also contributes to the dramatic increase of the loss factor at the hi gh temperature side of the ct relaxation peak for the BaTiO3/LDPE composite and functions practically even if there is no presence of VGCF.