Non-destructive condition monitoring of aged ethylene-propylenecopolymer cable insulation samples using dielectric spectroscopy and NMR spectroscopy
(English)Manuscript (preprint) (Other academic)
The causes of changes in dielectric response as a result of thermal and irradiative ageingof a cable insulation of ethylene propylene copolymer rubber containing 38 wt.% filler wereinvestigated. Samples were aged in three different combinations of irradiation dose rate andtemperature, 0.42 kGy h–1 at 85 °C, and 1.58 kGy h–1 at 55 and 85 °C, and subsequentlystudied by dielectric spectroscopy, NMR spectroscopy using a portable spectrometer andtensile testing. The extractable mass fraction and density were determined, and related to theimaginary part of the dielectric permittivity at 100 kHz. The ageing led to an increase in thedielectric permittivity, stiffness, density and degree of oxidation, together with a decrease inboth strain-at-break and relaxation time, as revealed by NMR spectroscopy. Except for thestrain-at-break, the properties changed in a linear fashion with increasing imaginary part ofthe dielectric permittivity at 100 kHz, with a particularly good agreement with respect to thedensity. As these properties are affected by the degree of oxidation, the results show that bothNMR using a portable spectrometer and dielectric spectroscopy can be used as conditionmonitoring techniques to detect the degree of oxidation in complex systems such as filledcopolymers.
Ethylene propylene rubber, Radiation ageing, Thermal ageing, Dielectric response, Portable NMR spectrometer, Condition monitoring
Textile, Rubber and Polymeric Materials
IdentifiersURN: urn:nbn:se:kth:diva-168192OAI: oai:DiVA.org:kth-168192DiVA: diva2:814647
FunderEU, FP7, Seventh Framework Programme
QS 20152015-05-272015-05-272015-05-29Bibliographically approved