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Long-term performance of poly(vinyl chloride) cables: mechanical and electrical performances and the effect of plasticizer migration
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Cables insulated with plasticized poly(vinyl chloride) were aged at temperatures between 80 and 180 °C in air and their conditions were assessed by indenter modulus measurements, tensile testing, infrared (IR) spectroscopy, differential scanning calorimetry (DSC) and liquid chromatography (HPLC). Electrical testing of oven-aged cable samples was performed in order to relate the electrical functionality during a high-energy line break accident to the mechanical properties and to establish a lifetime criterion. The mechanical data taken at room temperature after ageing could be superimposed with regard to ageing time and temperature. The ageing-temperature shift factor showed Arrhenius temperature dependence. The jacketing material showed an immediate increase in stiffness (indenter and Young’s modulus) and a decrease in the strain at break on ageing; these changes were dominated by loss of plasticizer by migration also confirmed by IR spectroscopy, DSC and HPLC. The core insulation showed smaller and also delayed changes in these mechanical parameters; the loss of plasticizer by migration was retarded by the closed environment and the changes in the mechanical parameters were due to chemical degradation (dehydrochlorination). Comparison with data obtained from this study and from other studies indicates that extrapolation of data for the jacketing insulation can be performed according to the Arrhenius equation even down to service temperatures (20-40 °C). Extraction of plasticizer of samples from cables that have been exposed to service for 25 years showed a minor decrease (within the margin of error) in plasticizer content with reference to that of unexposed cable samples. The low temperature deterioration of the jacketing is according to this scheme dominated by loss of plasticizer by migration.

Numerical analysis were performed on desorption data obtained by liquid chromatography. The fitting of the data to Fick’s law showed a transition between 100 and 120 ºC. This was interpreted as a change from evaporation-control of migration at low temperatures to a diffusion-control of migration at the higher temperatures.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , 47 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:38
Keyword [en]
Poly(vinyl chloride) cables, ageing, mechanical properties, plasticizer migration
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4405ISBN: 978-91-7178-712-5 (print)OAI: oai:DiVA.org:kth-4405DiVA: diva2:12168
Presentation
2007-06-05, E3, Osquars backe 14, 10044 Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101104Available from: 2007-05-29 Created: 2007-05-29 Last updated: 2010-11-04Bibliographically approved
List of papers
1. Long-term performance of poly(vinyl chloride) cables. Part 1: Mechanical and electrical performances
Open this publication in new window or tab >>Long-term performance of poly(vinyl chloride) cables. Part 1: Mechanical and electrical performances
2007 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 92, no 4, 617-629 p.Article in journal (Refereed) Published
Abstract [en]

Cables insulated with plasticized poly(vinyl chloride) were aged in air at temperatures between 80 degrees C and 180 degrees C and their conditions were assessed by indenter modulus measurements, tensile testing, infrared (IR) spectroscopy and differential scanning calorimetry (DSC). Electrical testing of oven-aged cable samples was performed in order to relate the electrical functionality during a high-energy line break (HELB) to the mechanical properties and to establish a lifetime criterion. The mechanical data taken at room temperature after ageing could be superimposed with regard to ageing time and temperature. The ageing-temperature shift factor showed an Arrhenius temperature dependence. The jacketing material showed an immediate increase in stiffness (indenter modulus and Young's modulus) and a decrease in the strain at break on ageing; these changes were dominated by loss of plasticizer by migration which was confirmed by IR spectroscopy and DSC. The core insulation showed smaller changes in these mechanical parameters; the loss of plasticizer by migration was greatly retarded by the closed environment, according to data obtained by IR spectroscopy and DSC, and the changes in the mechanical parameters were due to chemical degradation (dehydrochlorination). A comparison of data obtained from this study and data from other studies indicates that extrapolation of data for the jacketing insulation can be performed according to the Arrhenius equation even down to service temperatures (20-50 degrees C). The low-temperature deterioration of the jacketing is, according to this scheme, dominated by loss of plasticizer by migration.

Place, publisher, year, edition, pages
Royal Inst Technol, Sch Chem Sci & Engn, SE-10044 Stockholm, Sweden. Royal Inst Technol, Sch Elect Engn Electromagnet Engn, SE-10044 Stockholm, Sweden.: , 2007
Keyword
poly(vinyl chloride) cables, ageing, mechanical properties, plasticizer migration, DEGRADATION, PVC, STABILIZATION, POLYVINYL-CHLORIDE), POLYETHYLENE, TRANSITION, MORPHOLOGY, DIFFUSION
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-14087 (URN)10.1016/j.polymdegradstab.2007.01.005 (DOI)000246328200012 ()2-s2.0-33947709906 (Scopus ID)
Note
QC 20100713Available from: 2010-07-13 Created: 2010-07-13 Last updated: 2017-12-12Bibliographically approved
2. Long-term performance of poly(vinyl chloride) cables, Part 2: Migration of plasticizer
Open this publication in new window or tab >>Long-term performance of poly(vinyl chloride) cables, Part 2: Migration of plasticizer
2008 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 93, no 9, 1704-1710 p.Article in journal (Refereed) Published
Abstract [en]

Cable samples with plasticized poly(vinyl chloride) insulations were aged in air at temperatures between 80 and 155 degrees C. The concentrations of the plasticizer (di-(2-ethylhexyl) phthalate, DEHP) in the insulations of the aged cables were determined by extraction of samples in tetrahydrofuran followed by analysis of the extract by liquid chromatography. The plasticizer concentration data for different ageing times were analysed by numerical methods, fitting Fick's second law with a concentration-dependent diffusivity. The analysis showed that the transport of the plasticizer to the surrounding air phase was controlled by diffusion at 120 and 155 degrees C with an activation energy of 89 kJ mol(-1). The evaporation of the plasticizer from the outer boundary was rate controlling at lower temperatures (<= 100 degrees C), The rate of evaporation was initially constant and independent of the plasticizer concentration at both 80 and 100 degrees C. The activation energy for the initial DEHP loss rate from PVC at these temperatures was the same as that obtained for evaporation of pure DEHP on a glass plate at 60-100 degrees C measured by thermogravimetry, 98 2 kJ mol-1. Furthermore, the evaporation rate of pure DEHP on a glass plate was also of the same order of magnitude as the rate of plasticizer loss from the cable insulation. Extrapolation of the plasticizer loss rate data (from the cable at 80 degrees C and from pure liquid DEHP at temperatures between 60 and 100 IQ to 25 degrees C predicted a maximum loss of plasticizer of 1% over 25 years. This is in accordance with earlier presented data and with the data presented in this report.

Place, publisher, year, edition, pages
[Ekelund, M.; Azhdar, B.; Hedenqvist, M. S.; Gedde, U. W.] Royal Inst Technol, Sch Chem Sci & Engn, SE-10044 Stockholm, Sweden.: , 2008
Keyword
long-term prediction, evaporation, plasticizer migration, poly(vinyl chloride), BRANCHED POLYETHYLENE, PHTHALATE, POLYMERS, PVC, PARAMETERS, TRANSPORT, PRESSURE, KINETICS, HPLC
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-14089 (URN)10.1016/j.polymdegradstab.2008.05.030 (DOI)000259795600013 ()2-s2.0-50849127815 (Scopus ID)
Note
QC 20100713Available from: 2010-07-13 Created: 2010-07-13 Last updated: 2017-12-12Bibliographically approved

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