Effect of Electron Beam Irradiation upon and Electrical Conduction Mechanism for New Polymeric Materials

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Polyetheretherketon (PEEK) and polyimide (P1) that had been irradiated with an electron beam at 25, 50, 75, or 100 Mgy were used as samples. With PEEK, the conduction current of irradiated materials produced a small peak at a temperature between 200 and 210℃ and a space charge with a density that was not measurable by a PEA method was generated. Also, the conduction current decreased and the hopping distance shortened due to the cross-linking effect of irradiation. On the other hand, with P1, the conduction current of irradiated materials displayed a rapid increase around 250℃, but formation of the space charge was not observed. Next, the poling voltage (VィイD2pィエD2) was supplied at 0.5, 1.0, and 1.5 kV while the poling temperature (TィイD2pィエD2) was set at 100, 140, and 180℃ The temperature at which the thermally stimulated current (TSC) of the irradiated PEEK formed its peak shifted toward higher temperatures as the dose increased. Then, the bond energy was measured using an XPS apparatus and the chemical shift of these bonds was analyzed. As a result, as the dose increased, the strength of C-O and C=O bonds also increased, but that of C-C decreased. These results revealed that when an electron beam is irradiated, the cross-linking takes place, but the collapse takes place at the same time to increase the quantity of dipoles. In addition, the relationship between structural change and the formation of the space charge that resulted from the application of DC bias voltage (VィイD2bィエD2) was investigated through the use of the PEA method. When VィイD2bィエD2 was applied, an electric charge was injected through the electrodes and a homogenous space charge was generated, but the space charge was harder to generate as the dose increased.