Ionic Behavior of dc Conduction in Polyetheretherketone

The conduction process in polyetheretherketone (PEEK) is discussed mainly from the results of dc conduction, thermal pulse current (TPC), thermally stimulated current (TSC), and pulsed electroacoustic (PEA) measurements. It was found that dc conduction currents in PEEK are consistent with the values predicted by a theory based on the conventional thermally activated ionic hopping process. The ionic hopping distance was calculated to change from 2.5 to 3.9 nm when the temperature crosses the glass transition temperature. The results of TPC and PEA measurements show the existence of heterocharges in the vicinity of both electrodes. In TSC spectra, a peak appears at a temperature of ~ 5 to 20ºC above the biasing temperature. The peak position approaches to the constant temperature of 155°C when the biasing temperature is > 15CTC. The peak height is maximum when the biasing temperature is 150°C. It is considered that this peak is related to the glass transition and caused by the depolarization of ionic space charge. From these results, it is concluded that ionic carriers which may come from byproducts of synthesis play an important role in the dc conduction process in PEEK.