EB curing process
EB : electron beam ➞ accelerated e-
- No photoinitiators required ➞ minimized migration and low migration
- High degree of conversion
- Very high speed achievable allowing deep penetration for thick coatings
- N2 atmosphere needed to avoid O2 inhibition
- High energy radiation
- Improved dot gain control
- No heat for sensitive substrates
- Highest performances : gloss, scuff and abrasion resistance
- Suitable for highly pigmented formulations
➔ CURING OF THICK AND OPAQUE FILMS
➔ LOW RISK OF MIGRATION
Principle of technology
Inside an ultra high vacuum chamber,an incandescent filament generates electrons. Then, the electrons are accelerated by a strong electrical field and exit the chamber through a thin titanium window.
Two variables matter particularly, the intensity (number of electrons generated per second) applied to the filament and the tension applied to accelerate these electrons.
The key parameters
With the EB curing technology, there are two key parameters that you can tune separately and independently from each other :
- The dose (kGv) influences the flow of electrons: raising it is equivalent to increasing the the number of electron hitting a certain surface area
- The energy (kV) influences the penetration depth: increasing the energy is equivalent to amplifying the power of electrons that penetrate into the surface
Interaction with matter
Let us imagine an electron penetrating an acrylate monomer/oligomer formulation to approach the interaction with matter.
An electron comes from the top, some collisions occur while penetrating the substrate. That the results of energy generation, the electron loses his energy along the trajectory and this energy is deposited in the matter.
- The energy is high (or the coating is thin), the electron goes all the way through the substrate
- The energy is low (or the coating is thick), the electron is absorbed by the matter
When the energy is deposited (red crosses), secondary slower electrons (blue circles) may be generated; they are slower than primary electrons.
The low speed secondary electrons produced are solvated by the acrylate and allows the formation of a radical anion. Then, the protonation (coming from impurities or traces of water) of this radical anion generates a free radical species. A free-radical initiated specie is produced and allow the polymerization start.
Thus, a primary electron generates many free radicals that will initate the polymerization reaction. The higher the primary electron energy is, the more free radicals are generated.
The right curing materials for the best performance
Sartomer is a market-leading manufacturer of specialty acrylate resins designed for advanced UV, UV LED and EB curable systems:
|Chemical structure||Characteristics||Performance of the final cured film|
EB Curing R&D
Sartomer provides a unique service offering to help prospective customers perform feasibility studies in our lab.