Electrical and dielectric sensitivities to thermal processes in carbon nanofiber/high-density polyethylene composites

Owing to the huge interface region existing in a polymer nanocomposite, the effects of thermal processes on properties of nanocomposites are much more complicated than in a pure polymer. It is therefore important to determine the effects of thermal processes on nanocomposites with different interfacial interactions between the nanofillers and the polymer matrix. It is also important to explore the performance changes for nanocomposites under elevated temperatures over pure polymers. In this investigation, we examined the correlation of thermal treatment with dielectric properties of carbon nanofiber (CNF) reinforced high-density polyethylene nanocomposites. The thermal treatment of specimens was conducted for up to 120 h at 87°C and 127°C. Then, alternating current (AC) conductivity and dielectric properties were tested after definite intervals of time. Their changing rates over treatment time were analyzed. The results revealed the approximate linear relationships of AC conductivity and dielectric constant vs. heating time. Modified CNF reinforced nanocomposites had less influence by the heating treatments exhibiting better thermal resistance. The change rates of AC conductivity σ and dielectric properties have higher sensitivity to the treatment at a higher temperature. This study provides potential for further research on application of electrical and dielectric signals to detect the effects of heating process on lifetime of polymeric materials.