The impedance chracterisation of carbon black epoxy composites

Carbon black (CB) has been widely used as carbon filler for the epoxy resin to impart an enhanced electrical properties. CB is highly agglomerated; which is an important characteristic in enhancing the formation of percolated networks. In this work, CB has incorporated into epoxy at a loading range from 1 wt.% to 7 wt.%. The electrical conductivity is measured using impedance spectroscopy, operated in the frequency range between 10 to 10⁵ Hz. It is found that the higher amount of CB added resulted in the higher amount of electrical conductivity. The AC conductivity values and pattern for 1 wt.% and neat epoxy is similar, indicating that loading 1 wt.% is insufficient to change the behaviour of the epoxy from insulative to conductive. It is also observed that the specific conductivity values for the samples containing CB at loading 5 wt.% and above remains independent of the frequency, indicating a purely ohmic behaviour. The critical loading is also calculated and yielded the value of 2.7 wt.%. Impedance measurement is also performed and demonstrated Nyquist plot of semi circular for CB loading between 3 wt.% to 5 wt.%. However, the Nyquist plot for loading 6 wt.% and 7 wt.% displayed vertical plot.