Optimisation of radiation-curing coatings with silicone-based additives

Radiation-cured coatings, which are cured using UV or electron beam (EB) curing, are known for their fast curing times, environmental friendliness and high surface quality. They are used extensively in the printing and packaging industry, where they provide enhanced durability and visual appeal. However, to achieve optimal properties such as wetting, slip and mar resistance, specialised additives are required. Silicone-based additives play a critical role here by reducing surface tension and improving the leveling of the coating. This results in uniform, defect-free paint layers without cratering or pinholing.

Silicone polymers, especially polydimethylsiloxane (PDMS), tend to migrate to the surface of the coating due to their incompatibility with organic binders. While this migration improves wetting properties and prevents foaming, it can lead to undesirable effects. To circumvent this problem, PDMS molecules are chemically modified so that they bind into the lacquer matrix and provide lasting functional properties such as slip resistance and non-stick effects.

Silicone additives for organic coatings

The integration of silicone-based additives into organic coatings enables improved control of surface energy. This is particularly important for packaging coatings or functional coatings that need to be easy to clean or resistant to chemicals. The additives also improve the tape release function by creating a surface with low adhesion. It is essential that the coating formulation and the adhesives on the packaging films are compatible. Silicone additives prevent adhesives from adhering to the coating layer or leaving residues, which improves the quality of the end product and optimises processing.

Reading tip: Functional Coatings

Regulatory requirements and environmental aspects

Strict regulations must be observed when formulating new silicone-based additives. Particularly relevant here are the EU regulations on siloxanes (D4, D5, D6), which limit the content of these substances to below 0.1% in order to avoid classification as a substance of very high concern (SVHC). In addition, additives for packaging coatings must meet the requirements of the Swiss Ordinance on Materials and Articles to Ensure their Suitability for Food Contact. These stringent regulatory requirements call for innovative formulation technologies that combine environmental friendliness with high performance.

A key aspect for the effectiveness of these additives is their chemical reactivity. Modern silicone-based additives contain radical-crosslinkable groups that form covalent bonds with the coating during curing. This ensures that the functional properties are maintained over the long term and that migration into adjacent layers, such as adhesives or films, is minimised. New formulation technologies allow for more precise control of the chemical structure of these additives, so that they can be specifically optimised for different applications, from high-gloss coatings to functional protective layers.

Source: Eberhardt et al., PCI & BYK Chemie, 2025

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