Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications
Perfluoropolyethers (PFPE) are a class of frequently used lubricants in space applications due to their high stability under demanding conditions. However, they are susceptible to aging, with the aging mechanism being dependent on the specific material combination and storage condition. A Lewis-acid...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-02-01
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| Series: | Lubricants |
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| Online Access: | https://www.mdpi.com/2075-4442/11/2/81 |
| _version_ | 1797619774840111104 |
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| author | Milena Gleirscher Archim Wolfberger Sandra Schlögl Małgorzata Hołyńska Andreas Hausberger |
| author_facet | Milena Gleirscher Archim Wolfberger Sandra Schlögl Małgorzata Hołyńska Andreas Hausberger |
| author_sort | Milena Gleirscher |
| collection | DOAJ |
| description | Perfluoropolyethers (PFPE) are a class of frequently used lubricants in space applications due to their high stability under demanding conditions. However, they are susceptible to aging, with the aging mechanism being dependent on the specific material combination and storage condition. A Lewis-acid-induced thermo-catalytic degradation mechanism is of concern, for example, under steel-on-steel sliding contact, and can be relevant for long-term storage (LTS). Accelerated aging experiments were performed on Fomblin<sup>®</sup> Z25 and Krytox™ 143AC to investigate thermal stability under the influence of iron(III) fluoride (FeF<sub>3</sub>) at elevated temperatures (180 °C, 200 °C, and 220 °C) up to a total duration of 2000 h. The degradation effects were monitored via selected analysis techniques: mass loss of the samples due to degradation and subsequent evaporation during aging, FTIR spectroscopy to investigate changes to the chemical structure, dynamic viscosity measurements for the investigation of a potential impact due to changes in molecular mass, and a ball-on-disc tribological test setup to obtain friction behavior of the aged lubricants. Distinct differences between the two types of PFPE lubricants regarding stability to thermo-catalytic degradation were found. Fomblin<sup>®</sup> Z25 was highly affected by the presence of FeF<sub>3</sub> within the selected aging conditions, exhibiting high mass loss, a significant drop in dynamic viscosity, and an increased coefficient of friction due to degradation reactions. |
| first_indexed | 2024-03-11T08:32:35Z |
| format | Article |
| id | doaj.art-875412226fff49c2a1b2e41c232adc7f |
| institution | Directory Open Access Journal |
| issn | 2075-4442 |
| language | English |
| last_indexed | 2024-03-11T08:32:35Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Lubricants |
| spelling | doaj.art-875412226fff49c2a1b2e41c232adc7f2023-11-16T21:44:05ZengMDPI AGLubricants2075-44422023-02-011128110.3390/lubricants11020081Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space ApplicationsMilena Gleirscher0Archim Wolfberger1Sandra Schlögl2Małgorzata Hołyńska3Andreas Hausberger4Polymer Competence Center Leoben GmbH (PCCL), Roseggerstraße 12, 8700 Leoben, AustriaPolymer Competence Center Leoben GmbH (PCCL), Roseggerstraße 12, 8700 Leoben, AustriaPolymer Competence Center Leoben GmbH (PCCL), Roseggerstraße 12, 8700 Leoben, AustriaESA-ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The NetherlandsPolymer Competence Center Leoben GmbH (PCCL), Roseggerstraße 12, 8700 Leoben, AustriaPerfluoropolyethers (PFPE) are a class of frequently used lubricants in space applications due to their high stability under demanding conditions. However, they are susceptible to aging, with the aging mechanism being dependent on the specific material combination and storage condition. A Lewis-acid-induced thermo-catalytic degradation mechanism is of concern, for example, under steel-on-steel sliding contact, and can be relevant for long-term storage (LTS). Accelerated aging experiments were performed on Fomblin<sup>®</sup> Z25 and Krytox™ 143AC to investigate thermal stability under the influence of iron(III) fluoride (FeF<sub>3</sub>) at elevated temperatures (180 °C, 200 °C, and 220 °C) up to a total duration of 2000 h. The degradation effects were monitored via selected analysis techniques: mass loss of the samples due to degradation and subsequent evaporation during aging, FTIR spectroscopy to investigate changes to the chemical structure, dynamic viscosity measurements for the investigation of a potential impact due to changes in molecular mass, and a ball-on-disc tribological test setup to obtain friction behavior of the aged lubricants. Distinct differences between the two types of PFPE lubricants regarding stability to thermo-catalytic degradation were found. Fomblin<sup>®</sup> Z25 was highly affected by the presence of FeF<sub>3</sub> within the selected aging conditions, exhibiting high mass loss, a significant drop in dynamic viscosity, and an increased coefficient of friction due to degradation reactions.https://www.mdpi.com/2075-4442/11/2/81liquid lubricantsperfluoropolyetherPFPEaccelerated agingthermo-catalytic degradationlong-term storage |
| spellingShingle | Milena Gleirscher Archim Wolfberger Sandra Schlögl Małgorzata Hołyńska Andreas Hausberger Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications Lubricants liquid lubricants perfluoropolyether PFPE accelerated aging thermo-catalytic degradation long-term storage |
| title | Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications |
| title_full | Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications |
| title_fullStr | Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications |
| title_full_unstemmed | Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications |
| title_short | Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications |
| title_sort | accelerated thermo catalytic degradation of perfluoropolyether pfpe lubricants for space applications |
| topic | liquid lubricants perfluoropolyether PFPE accelerated aging thermo-catalytic degradation long-term storage |
| url | https://www.mdpi.com/2075-4442/11/2/81 |
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