Novel Effect Photoinitiators
A novel approach is being pursued by Ciba to obtain additional surface effects in UV-cured coatings. The combination of surface-active substituents, as part of the initiating species, and the modification and optimization of the chromophore give rise to a new class of photoinitiators that provide improved performance and efficiency when compared to state-of-the-art photoinitiators as well as additional effects.

The optimized balance of UV-spectral properties, molecular weight, spacer functionality and choice of surface-active side chains within a single initiator enables a very fast UV curing process that yields a high polymer crosslink density at the surface. This leads to improved resistance towards scratches and low yellowing. The novel system is particularly well suited to high performance applications such as automotive clear coats, where the fine-tuning of surface properties, such as scratch resistance, is highly desirable.

Nano-Particles and Coatings
Surface and bulk properties of coatings can be improved by adding nano-particles as fillers. For extremely small particles (diameter < 100 nm) any negative influence on the transparency and gloss of the coating must be avoided. Ciba R&D is currently developing inorganic nano-particles to improve the scratch resistance of automotive clear coats.

These particles are synthesized either by “top-down” approaches (surface modification of existing particles) or by “bottom-up” approaches (in-situ synthesis of modified particles), using Ciba in-house knowledge of synthetic chemistry and specialty polymers. For example, specific surface modifications are necessary in order to make the nano-particles compatible with the organic matrix of the coating, and hence to avoid agglomeration. Other interesting surface effects such as super-hydrophobicity and anti-reflectivity can also be observed