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varnish and sol-gel multifunctional ProtectIve cLear cOat for aeronauTics

Periodic Reporting for period 3 - PILOT (varnish and sol-gel multifunctional ProtectIve cLear cOat for aeronauTics)

Reporting period: 2019-06-01 to 2019-11-30

PILOT, acronyms of varnish and sol-gel multifunctional Protective cLear cOat for aeronauTics, aims to develop two types of coating, a UV hybrid silicone varnish and a hybrid sol-gel coating, that are resistant enough to protect wings from environmental damaging. The main goal will be to develop an optically transparent functional clear coat applied over a final paint scheme to protect plane surfaces. This clear-coat shall be resistant enough to keep the laminar properties of the wings of plane including leading edge as well as fairings at their optimum and prevent any increase of drag during service life. The main performance of this topcoat will be:Anti-erosion properties (rain and sand), Anti-icing performance, Anticontamination performance and Anti-static properties.

This means that the developped materials should satisfy the following technical challenges :
- adhesion to polyurethant top-coat.
- chemical resistance.
- ageing resistance to UV and temperature.
- mechanical resistance to scratch, abrasion.
- reistance to liquid erosion.
- being anti-ice and anti-contamination (limit their adhesion).
- being processable by psray.
- being cured at low temperature.

and for the overall cleansky objectives :
- design eco-friendly material and concept.
- reduce process duration and process.
- improve innovation and integration of new knowledge.
"The aim of WP1 is to manage the project in terms of communication, IP, data management and administrative management. For the 3rd period, all the deliverable were done and edited : 3rd periodic report and D1.4 Final Dissemination & report sum up these activities. Several Audio conference and email exchange were performed with the topic manager and technical officer to insure that project will be finished on time.

The aim of Work package 2 was to perform a literature review and edited in the deliverable D2.1 ""literature review report"". This Work package was realized during the 1st period.

The aim of Work package 3 , which is the most important of the project, is to:
- Develop the two coating solutions (hybrid silicone technology and sol-gel technoloogy) by both partners based on WP2 road map.
- Implement their process.
- Validate that their properties fit the specification.
This work package was realized during the 3 period of the project.

After evaluating ""on the shelf"" coating and their drawbacks during 1st period, coatings were improved :
Concerning the UV hybrid silicone, critical thickness was identified at 25 µm. Characterization tests have shown the main strength of the silicone hybrid coating as water repellence, flexibility, hardness and optical clarity. It has also showed its inertia against water immersion. The major drawback is adhesion. This drawback had been studied during the second period of the project.
Concerning sol-gel solution, the coating presents relevant properties in terms of whydrophobicity and brightness but their properties need to be improved in order to present enhanced adhesion and mechanical performance (resistance to scratch and abrasion, erosion resistance). Consequently, these first tests highlighted that:
- poor wettability and adhesion on the polyurethane basecoat.
- sol-gel solutions are brittle and rigid. These phenomenon are mainly due to the coating thickness, curing and mechanical properties. After curing stress relaxation forces appear through the coating, which lead to the apparition of cracks.
- Optical properties satisfy specification.
- poor mechanical properties.
- poor hydrophobic properties.
These improvements had been studied during the second period.

The implementation of Rescoll and Elkem formulation and their properties were summed up in the deliverable D3.1 D3.2 D3.3 (submitted during 2nd period) and D3.4 which was edited and submitted during the 3rd period.

In the last period, Coating had been validated according to topic manager specification and to the road map defined in D2.2 ""development work report"".
Then samples were fabricated to ensure the realization of WP4 -Qualification tests. The deliverable D3.5 ""Small batches coating production & control"" summed this fabrication phase.

WP4 was dedicated to coating qualification and had been performed during all the last period duration. This WP enabled to characterize the coatings performance according to the topic manager specification. Coating properties had been characterized in terms of adhesion, resistance to mechanical stress, resistance to chemicals and ageing. the deliverable D4.1 summed up all these results.

Lacem start to be involved in the project during the second period. Their role is to developp a liquid erosion test rig. After having performed a bibliographic study on existing liquid erosion theory and device, LACEM designed the test rig in order to answser topic manager and partners needs. the conception of the test rig started at the end of the second period. As a consequence a delay accured in the development of such device. At the end of the second period, the device is still not available.
In the last period, LACEM tried to solve the issues that were identified : vibration of the test rig at high velocity, safety for user. Unfortunatly, it was not possible during the last period to entirely solve both issue. At the end of the period, the liquid erosion test rig was not fully operational. As a contingency plan, it was decided in agreement wih the topic manager to sub-contract erosion test."
"At the end of the project, the PILOT consortium confirms that the information of how our project will contribute to the expected impacts is still relevant. At the end of the last period, both coatings (RESCOLL and ELKEM) satisfy technical objectives and overall cleansky objectives. According to the obtained results, both partners started introducing the ""as developped"" technology to other customer. RESCOLL will evaluate the coating in an H2020 european project. The application will be to protect rolls used for coil coating application technique. ELKEM will evaluate coating in windturbine industry.

Concerning Impact, at the end of the project, Most of the technical objectives were achieved :
- Adhesion
- Chemical resistance
- Ageing resistance
- Mechanical resistance
- Anti-icing/ anti contamination
- Anti-static
- Sprayable
- Lower temperature process

Liquid erosion process will be validated once sub-contracting will be done (outside of the project duration).

Concerning overal Cleansky objective, the following objective were achieved :
- Eco-friendly design and concept : no hazardous product were used.
- Reduce process duration and temperature : curing with UV for short duration.
- Improve innovation and integration of new knowledge : erosion test, UV curing."