Reactive polyurethane nanoparticles for radiation curing and redox-based coating materials

 
A new patented in-situ process enables the production of low-viscosity and solvent-free functionalized polyurethane nanoparticles in commercially available reactive diluents. By varying the process parameters, the molecular weights, the particle size and the mechanical properties can be specifically controlled for the application in coating materials. Depending on the composition of the polyurethane nanoparticles, highly transparent, storage-stable and weathering-resistant coatings with an excellent adhesion strength as well as scratch resistance on different substrates arise. The present contribution investigates the fundamental possibility of using functionalized polyurethanes of different compositions in UV-curing clear varnishes. For this purpose, mixtures with commercially available radiation-curing resins were prepared and coated by spraying. The clear varnishes were subjected to different tests such as Martens hardness, Martindale test, König pendelum damping test as well as adhesive strength on different substrates. The results reveal a very good compatibility with commercially available UV-hardening resin systems as well as enhancements of the mechanical properties such as the scratch resistance. In addition, it is possible to formulate styrenefree redox systems for thick-layer applications of high gloss.