Open AccessInfluence of surface fluorination temperature on space charge accumulation in polyethylene
Author(s) -
Chuanzhong Xuan,
Zhenlian An,
Chenxia Liu,
Yewen Zhang,
Zheng Fei-Hu
Publication year - 2012
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.61.138201
Subject(s) - materials science , space charge , polyethylene , analytical chemistry (journal) , volume (thermodynamics) , diffusion , surface charge , electrode , permittivity , dielectric , composite material , chemistry , thermodynamics , electron , organic chemistry , physics , optoelectronics , quantum mechanics
Polyethylene (PE) discs prepared by hot-pressing, each with a thickness of 0.8 mm, are surface fluorinated in a laboratory vessel by an F2/N2 mixture containing 12.5% F2 by volume at different temperatures of 35, 55, and 70 ℃ for the same time of 2 h. The influence of fluorination temperature on space charge accumulation in PE is investigated by the pressure wave propagation method. The results show an obvious decrease in space charge accumulation in the fluorinated sample subject to a direct current high voltage with the increase of fluorination temperature, and there exists almost no charge accumulation in the sample fluorinated at 70 ℃. Attenuated total reflection infrared analyses indicate a substantial change in chemical composition of the sample surface layers by the fluorinations and an obvious increase in degree of fluorination with fluorination temperature increasing. Contact angle measurements and surface energy calculations indirectly indicate a significant increase in permittivity of the fluorinated layers by the fluorinations. Open-circuit thermally stimulated discharge current measurements further reveal different charge trapping properties of the fluorinated layers and the improved barrier properties of the fluorinated layer to the diffusion of the chemical species from the semi-conductive electrode to the PE with increase of fluorination temperature, thus indicating a corresponding decrease in free volume of the surface layer. The decrease in the free volume plays a more important role in suppressing the space charge accumulation, compared with the increase in permittivity and the change in charge trap.