Title :
Effect of the physical ageing on electrical conductivity and dielectric measurements of amorphous poly(ethylene terephthalate)
Author :
Colomer, P. ; Calaf, J. ; Belana, J. ; Montserrat, S.
Author_Institution :
Escuela Tecnica Superior de Ingegieros Ind. de Terrassa, Univ. Politecnica de Catalunya, Barcelona, Spain
Abstract :
Electrical conductivity and dielectric relaxation measurements have been carried out during the physical ageing of amorphous poly(ethylene terephthalate) in the range of ageing temperatures T a between 50 and 70°C and ageing times t a between 10 min and 72 h. Both the intensity of the current and the imaginary part of the complex dielectric permittivity ∈" (or dissipation factor tan δ) decrease with ta, at Ta constant, as a consequence of the structural relaxation of the material, reaching a constant value in a time which depends on the temperature. As T a increases, the decay of the intensity and ∈" (or tan δ) increases as a consequence of the greater extension of the relaxation which shows a maximum in the interval 60-65°C for t a⩾6 h
Keywords :
ageing; dielectric losses; dielectric relaxation; electrets; electrical conductivity of amorphous semiconductors and insulators; permittivity; polymer structure; polymers; 50 to 70 degC; PET; ageing temperatures; ageing times; amorphous poly(ethylene terephthalate); complex dielectric permittivity; dielectric relaxation; dissipation factor; electret; electrical conductivity; physical ageing; structural relaxation; Aging; Amorphous materials; Conductivity measurement; Dielectric measurements; Electric variables measurement; Permittivity; Polymers; Positron emission tomography; Temperature dependence; Thermal conductivity;
Conference_Titel :
Electrets, 1991. (ISE 7) Proceedings., 7th International Symposium on (Cat. No.91CH3029-6)
Conference_Location :
Berlin
Print_ISBN :
0-7803-0112-9
DOI :
10.1109/ISE.1991.167207