Typical UV curable resins consist of oligomers, monomers, photoinitiator and various additives. 

The mechanism for forming the coating includes 3 basic steps: initiation -  chain propagation - chain termination.
During the initiation step, the interaction of a photoinitiator with light induces the formation of a radical which reacts with a monomer to give an active monomer. This active monomer is then propagated to build growing polymeric chain radicals.

Depending on the nature of the monomers and more precisely on their weight or functionality, it is possible to play on the cross-linking density and as a result on the flexibililty or the hardness of the network. 

The incorporation of additives allows to manage and optimize the properties. Epoxy based coatings are recognised as durable resistant UV curable layers offering barrier properties. 

The combination of this organic layer with inorganic sol-gel precursors is an innovative and interesting way to combine the advantages of organic and inorganic matrix.


Very fast cure speed
Easy application
Reduced energy consumption for cure
Little space requirements
Application for heat sensitive substrates possible

Impact resistance - ISO6272

Scratch resistance - ISO 1518
Scratch does not reach the substrate.

Flexibility - ISO 1519


In CHOPIN, UV varnish formulations were tailored with appropriate alcoxysilanes precursors to adjust the wettability and the repellence properties of the coatings. 

The organic/inorganic parts ratio strongly impact the mechanical and the barrier properties of the layer. It is therefore really important for the future applications on edge aircraft.

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