Crystallization and dielectric properties of carbon nanofiber/high-density polyethylene composites

An attractive type of nanofiller-carbon nanofiber (CNF) was used to modify high-density polyethylene (HDPE), in which the nanocomposites with 1%-20% CNFs were prepared via a two-step process including melt mixing and hot press. The crystallization and dielectric properties of CNF/HDPE composites, as well as the dispersion of CNFs, were investigated. The results showed that CNFs were well dispersed in HDPE. It was also demonstrated that the crystallinity and crystal size of HDPE were influenced by the introduction of CNFs. The (110) planes of HDPE was also enhanced as proved with the increased intensity of the characteristic peak. In addition, the dielectric constant of nanocomposites was dramatically improved with higher CNF contents. The highest dielectric constant, 580 at 103Hz, was achieved with 20% CNFs, which was about 150 times higher than that of pure HDPE. Simultaneously, the dielectric constant of nanocomposites showed high dependence on the frequency due to the existence of CNFs, compared with the independent dielectric constant of pure HDPE. The AC conductivity of nanocomposites was also greatly affected by CNF, the characteristic of direct conductivity was obviously exhibited with the CNF concentration higher than 10%.