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Deterioration of highly filled EPDM rubber exposed to thermal ageing in air: kinetics and non-destructive monitoring
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0003-3049-7225
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0002-0231-3970
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The effects of thermal ageing on EPDM cable transit seals were investigated. Samples were aged in air at 110, 120, 150 and 170 °C, and evaluated with tensile testing, indenter modulus profiling, oxidation profiling (using IR spectroscopy), nuclear magnetic resonance (NMR) spectroscopy profiling. The ageing resulted in an increase in the indenter modulus, the degree of oxidation and in a decrease in the NMR transverse relaxation time, T2. Diffusion-limited oxidation (DLO) occurred with a large oxidation gradient close to the sample surface. The portable NMR MOUSE (non-invasive method) was used to obtain detailed degradation profiles, up to a depth of 5 mm of the aged samples. The results indicated a deterioration process that was attributed to several mechanisms, i.e. oxidation, anaerobic crosslinking and migration of oil extender. By combining the data acquired from the profiling, separation and quantification of these three contributing mechanisms was determined. Additionally, it was shown that the portable NMR data correlated well with the strain at break data, highlighting the potential use of the portable NMR for condition monitoring.

Keyword [en]
Ethylene propylene rubber, Thermal ageing, Portable NMR spectroscopy, Modulus profiling, Condition monitoring
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-213010OAI: oai:DiVA.org:kth-213010DiVA, id: diva2:1136329
Projects
Long-term performance of polymeric materials in nuclear power plants
Note

QC 20170829

Available from: 2017-08-27 Created: 2017-08-27 Last updated: 2017-08-29Bibliographically approved
In thesis
1. Long-term performance of polymeric materials in nuclear power plants.
Open this publication in new window or tab >>Long-term performance of polymeric materials in nuclear power plants.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Access to energy is crucial for modern societies to function sustainably. In addition, nuclear power has for a long time been considered a reliable source of energy. However, the majority of nuclear power plants are reaching the end of their service lifetimes, and it is crucial to verify that every component can withstand the added service time. With the ability to monitor the condition of components and perform lifetime predictions, suitable maintenance and safe operations can be achieved.

The specific focus of this study was on ethylene-propylene diene (EPDM) rubber sealants with high filler content, which are replacing halogen-containing polymers. Two types of EPDM seals were studied: Lycron (Brattbergare), which is used in cable transit seal systems in reactor containment, and a carbon black-filled EPDM rubber sealant installed in a transportation valve for transporting old/spent nuclear fuel situated underwater in a reactor basin.

The changes that occur in EPDM cable transit seals during thermal ageing and the causes of these changes were investigated. Samples were tested at different temperatures between 110 °C and 170 °C and evaluated with respect to the distance from the surface via modulus profiling, infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The results showed the existence of three different deterioration mechanisms during ageing. By combining the different profile parameters, it was possible to quantify the contributing mechanism and to obtain information about the kinetics of the different processes. The effects of γ-irradiation on the EPDM cable transit seals in media with different oxygen partial pressures (1 – 21.2 kPa) were studied. By employing different profiling methods, it was possible to separate the mechanisms: polymer oxidation, migration of molar mass species and anaerobic changes in the polymer network. Additionally, the migration process during γ-irradiation was found to be accelerated for higher oxygen partial pressures. The effects of radiation on carbon black-filled EPDM seals in air and water were studied via irradiating samples at high dose rates (7 kGy/h) up to 3.5 MGy. This is the first study on the cross-sectional profiles of highly filled EPDM materials exposed to radiation in water, and it shows great differences in the chemical and physical properties of the material after irradiation in air and water. Of particular interest in this study were the use of a non-invasive portable NMR sensor (NMR-MOUSE) to acquire spatially resolved information from samples and the investigation of this promising method for onsite condition monitoring tests. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 93
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:31
Series
TRITA-CHE REPORT, ISSN 1654-1081 ; 2017:31
Keyword
EPDM, thermal ageing, radiation ageing, portable NMR spectroscopy, modulus profiling, condition monitoring, plasticizer migration
National Category
Polymer Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-213361 (URN)978-91-7729-460-3 (ISBN)
Public defence
2017-09-22, Q2, osquldas väg 10, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Long-term performance of polymeric materials in nuclear power plants
Funder
Swedish Radiation Safety AuthorityVattenfall AB
Note

QC 20180829

Available from: 2017-08-29 Created: 2017-08-29 Last updated: 2017-08-29Bibliographically approved

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Pourmand, PayamHedenqvist, Mikael S.Furó, IstvanGedde, Ulf W

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