Radical Photopolymerization

The starting point for radical photo-curing silicone acrylates is the photolytic decay of a photoinitiator, yielding a high concentration of radicals which is necessary for chain propagation. We recommend a specially modified 2-hydroxy ketone, as this is highly efficient with the emission spectra of standard UV lamps (medium pressure mercury lamps) and is additionally showing an improved performance with TEGO^® RC Silicones. It is available under the name TEGO^® Photoinitiator A17.

The units for the polymerization reaction are acrylic groups along the silicone backbone. The overall process of radical generation and cross-linking is very rapid and efficient. At room temperature, the reaction is completed within microseconds, which guarantees high processing speeds. The reaction is very robust and a number of additives can be included directly into the silicone formulation to change gloss, roughness, colour, friction, anchorage or viscosity.

The polymerization process is stopped when all acrylate groups are consumed or the radical center is quenched with oxygen. Since oxygen is a polymerization inhibitor, good inerting of the reaction chamber with nitrogen is an important factor for the final properties of the release coating.