Community Research and Development Information Service - CORDIS


ADONIS Report Summary

Project reference: 632446
Funded under: FP7-JTI

Periodic Report Summary 1 - ADONIS (Analyzing Durability Of iNsulating materIalS)

Project Context and Objectives:
The ADONIS project deals with the study and durability of electrically insulative material in aircraft engine chemical environment. This environment includes high temperature, hydrocarbide fluids and hydraulic systems fluids and is very aggressive for materials. The aim of this project is to study the aging of the materials of interest in these conditions in terms of chemical, mechanical and insulating properties.
Some resins and insulating polymers have been selected for this study and can be classified as following:
- Epoxy resins
- Silicone resins
- Polyamide-imide resins
- Polyimide film
- Polyamide film
- PEEK film
Chemical, thermal and mechanical properties are measured at different stages of aging and compared to initial state materials in order to determine the impact of aircraft engine chemical environment.
Finally, interface between resins and sheets of metal or wires is studied.

Project Results:
WP 1: Management
Technical work of ADONIS project was managed by a RESCOLL engineer under the supervision of the characterization department director. Analyses were performed by RESCOLL’s technicians and all results interpretations and reports were performed by two doctors in analytics.
Technical reports were regularly sent to the topic manager by email especially during the work package 4 with the curing of resins and the validation of tests.
Two face to face meetings were organized during this period. At the beginning of the project (on the 15th of April 2014) to define the objectives and discuss the draft of test plan. A second meeting was organized at RESCOLL on the 16th of February 2015 to present and discuss the first results, to show the laboratory means and the tests conditions.
WP 2: state-of-the-art of organic polymers and interfaces durability tests
ADONIS project began with a state-of-the art of similar materials aging. The aim was to collect adapted characterization techniques and information about degradation of the materials selected for the project. This work started at the beginning of the project in April 2014 and finished in July 2014 with the writing of a report (deliverable D1). This deliverable was sent to the topic manager the 8th of July. Deliverable D1 was submitted to the JTI the 26th of September.
WP 3: Polymer and interface hydrocarbide aging test planning
In July and August 2014, the project planning started. Suppliers were contacted by RESCOLL’s engineers to obtain the different materials and advices for their curing and use. Delays were sometimes quite long to receive samples and/or information, leading to a small delay for the following work package. This work result in a materials test plan that was defined in deliverable D2.
This deliverable was submitted to the topic manager on the 22nd July 2014 and validated for the European commission on the 26th September 2014.
WP 4: Material sample and interface tests vehicles processing and characterization
This work package was quite long due to difficulties with some resins to obtain good curing procedures. It started in September 2014 with the first materials and finished in April 2015. The deliverable D3 was sent to the topic manager on the 19th February 2015.
The aim of this part was to cure the resins and to perform the initial state characterization of all materials.
Curing of silicone A resin was quite difficult as oxygen, latex and wood inhibit the crosslinking. After several of tests, it appeared that the curing had to be performed under vacuum and with a lid to avoid sticky surface of the cured resin.
Curing of silicone B was easier and is performed for 16h at 180°C.
Curing of epoxy A resin also required several trials. The resin is cured with a hardener at high temperature under vacuum and stirring. It was difficult to obtain a homogeneous mixing of both components and the characterization results were more heterogeneous than the ones of other resins. After some optimization of the process, the reproducibility of the curing was better. After discussion with SAFRAN in February 2015, it was decided to keep this process even if the mixing was not perfect.
Curing of epoxy B resin was performed for 75min at 160°C followed by 120min at 180°C.
The most complicated curing procedure was the one of polyamide-imide resin. This material is supposed to be cured as a thin film directly on the final substrate. As we needed to study this resin without substrate, the work was very complex to perform. The first step of curing is the evaporation of solvent. The supplier suggested to let the resin at 70-80°C during several hours; however, shrinking was observed. The film thickness was then bigger and the solvent only evaporates from the surface. The final curing at 250°C lead to several bubbles at the surface of the film. The solution was to let the solvent evaporate at room temperature for several days. The results were not reproducible and specimens were not homogeneous. As for epoxy A resin, it was decided in February 2015, with the agreement of SAFRAN, to perform the tests with these specimens as there was no other solution to obtain better results.
WP 5: Aging study and interpretation
This work package was separated in two stages. The first stage was a preliminary aging of all materials performed at 170°C. This temperature is an average value characteristic of engine environment. The aim of this first aging was to observe the behavior of the materials. The aging temperature has to be high enough to induce degradation but not too high to avoid quick and total decomposition of the material. The second stage is the final aging of the materials at the adequate temperature depending on the results obtained during the first stage.
The analysis of the aged samples was performed according to the test plan defined on WP 3.
Potential Impact:
WP 2: state-of-the-art of organic polymers and interfaces durability tests
Materials aging were described in several studies. Even if it was not possible to get information about the same resins as the one selected for ADONIS project, some general results were obtain.
Epoxy resins degradation seems to start from 250°C due to bond scission and leads to a decrease in glass transition temperature, a color change, and weight and adhesion losses. They are also strongly affected by immersion in hydraulic fluids.
Silicone resins seems to be stable until 365°C. Immersion in jet-fuel leads to an important absorption and a strong decrease in strength.
Polyamide-imide resin degradation was not really described in the literature. Only one article was found and showed a thermal degradation starting from 260°C.
Polyimide film degradation starts from 500°C and is characterized by oxidation of the surface and bond scission.
Polyamide film studied by TGA measurement shows a degradation process starting around 420°C. At lower temperature, absorbed moisture is released and a change of color is observed due to bond scission releasing water molecules around 270°C.
Finally, PEEK film degradation seems to start around 580°C with bond scission. Immersion in oil shows a small mass uptake lower than 1% and oil acts as a plasticizer.
This work package led to the milestone S1 at the end of July. The analytical techniques selected for the project were:
- TGA, to follow the weight loss
- DSC, DMA and TMA to measure Tg and other properties (enthalpy, modulus, ...)
- Infrared, to observe chemical modification
- Dielectric spectroscopy, to measure permittivity and other electrical properties
- Mechanical tests, to follow specific mechanical properties
WP 3: Polymer and interface hydrocarbide aging test planning
The test plan corresponding to this work package was proposed as follow in the deliverable D2:
- Curing of resins
- Initial characterization of resins and films (including weight measurements, infrared spectroscopy, thermal analyses, electrical properties and mechanical tests)
- Preliminary aging in oil to determine the adequate temperature of aging
- Characterization after preliminary aging
- Main aging at the adequate temperature for each material
- Characterization at different stages of aging
- Interface study and aging
- Spray aging test
WP 4: Material sample and interface tests vehicles processing and characterization
For all materials polymerization procedures were suitably adapted even if for PA the results were not reproducible. In case of PA it was decided, in agreement with the topic manager, to proceed with further tests as no other back up material was available at SAFRAN for this application.
All materials were characterized using infrared, DSC, DMA and TGA. It was not possible to analyze silicone resins by DMA as the specimen were too brittle and glass transition was not always observed by DSC. TMA analysis was then performed on silicone resins. For films, mechanical tests were performed. Dielectric measurements were also done but these test were not relevant and abandoned.
The milestone of sample testing was 80% reached in March 2015. The initial characterization of materials was finished in April 2015. The preparation and characterization of interfaces was delayed due to the fact that good curing of resin was long to achieve.
WP 5: Aging study and interpretation
The stage one aging started in November 2014 for the films and in February 2015 for the last resins (epoxy A and polyamide-imide). It lasted several weeks and was followed by a characterization of all materials for a comparison with initial state characterization. The results are summarized in the following table.
Materials Aging time Weight evolution Glass transition evolution Infrared
Silicone A 9 weeks + 5,5% Decreasing (TMA)
Stable + new transition (DSC) Oil absorption
Silicone B 3 weeks + 13% Decreasing Oil absorption
Epoxy A 3 weeks - 0,5% Decreasing (DSC) Oil absorption
Epoxy B 8 weeks - 2% Increasing (DMA)
Decreasing (DSC) Formation of amide and carboxylic acids
Polyamide-imide resin 2 weeks Not exploitable Increasing No differences
Polyimide film 2 weeks - 3,5% New transition (DMA) No differences
PEEK film 2 weeks + 1,5% New transition Oil absorption
Polyamide film 2 weeks + 16% Decreasing Oil absorption

According to this preliminary aging study, final aging conditions were determined:
- Silicone A : final aging at 200°C
- Silicone B : final aging at 150°C
- Epoxy A : final aging at 200°C
- Epoxy B : final aging at 170°C
- Polyamide-imide : final aging at 170°C
- Polyimide : final aging at 200°C
- PEEK : final aging at 200°C
- Polyamide : final aging at 200°C

In March 2015, the final aging started for specimen aged at 200°C. Exposure of oil at high temperature lead to high amount of vapors. As it was not possible to use 3 ovens under aspiration, it was decided not to perform further study on silicone B resin. This material was already affected by oil immersion at 170°C, it has a lower resistance under engine environment than the other and consequently was not a priority. In April 2015, this work package was finished at 40%.


Sipos, Konstantin (Head of R&D Department)
Tel.: +33 628330257
Record Number: 187701 / Last updated on: 2016-08-23