Abstract
Electrical conductivity (·) enhancement, control, aging stability, and linear relation between · and reciprocal temperature (1/T) in PTFE (Teflon) had been examined by homogeneous low potential electron beam irradiation (HLEBI). Irradiations up to 0.432MGy were found to raise the · of PTFE more than two orders of magnitude. In addition, control of electron movement or Fermi level by HLEBI on polymers seems possible since at low HLEBI levels up to 0.216MGy, a strong dependence on · was observed. Aging stability investigation showed the saturated conductivities at 10 6 s( ·s) (2.5 © 10 ¹16 and 3.6 © 10 ¹15 Sm ¹1 ) obtained at EB doses of 0.0432 and 0.432MGy, respectively were approximately 4.9 and 70.6 times higher than · of untreated PTFE (5.1 © 10 ¹17 Sm ¹1 ). Although the aging initially reduced the · of irradiated samples, ·s were remarkably higher than the untreated. For example, the lower dose 0.0432MGy samples decayed significantly, but its ·s value (2.5 © 10 ¹16 Sm ¹1 ) was still about 490% above untreated condition at 5.1 © 10 ¹17 Sm ¹1 . ESR (electron spin resonance) measurements showed aging for 10 6 s only slightly reduced the peak intensity of irradiated PTFE. This indicated the charge carriers generated did not easily decay. Results agree with the literature where PTFE was irradiated with VUVand radicals such as CF3 + did not substantially decay with aging. Since the slopes of linear relationships between logarithmic electrical conductivity (ln·) and reciprocal temperature (1/T) of all PTFE samples irradiated were approximately equal to that before treatment from 303 to 375K, HLEBI didn’t convert the · system. The small irradiation dose of 0.0432MGy raised the electrical conductivity at room temperature. At higher temperatures above ³375K, the 0.0432 and 0.432MGy-HLEBI generated drops in conductivity ·. When unstable dangling bonds with isolated radicals at terminated sites are assumed to be formed in irradiated PTFE, the · recovery by heating to 424K as well as high · of irradiated PTFE could be explained. HLEBI probably generated dangling bonds in the form of radicals acting as acceptors to carry charge. Since a chemical dopant was not needed to act as a charge carrier, HLEBI could probably be an attractive method to attain homogeneous doping of organic films. [doi:10.2320/matertrans.M2011273]
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