In this study, UV curing of polysilazane-based coating systems highly filled with metallic fillers for corrosion protection applications was examined. The UV curing was carried out using the thiol-ene “click” reaction. Therefore, a tetra-functional thiol crosslinking agent and a photoinitiator were added to the polysilazane to accomplish the radical crosslinking reaction. The UV-cured coating systems were compared to thermally cured samples regarding mechanical properties and chemical resistance. The mechanical properties were studied by scratch tests and hardness measurements and the chemical resistance by immersion in toluene and isopropanol. Contact angle measurements were carried out before and after the chemical resistance tests. Surprisingly, it was found that despite the high amount of metallic particles, the entire filled coating was cured by UV irradiation. The mechanical properties of the UV-cured systems were slightly worse compared to the thermally cured coatings. However, both curing methods led to a very good chemical resistivity of the coatings against the liquid polar and nonpolar media. Contact angle measurements revealed that by UV curing more hydrophobic coatings are achieved due to prevention of oxidation of the metallic fillers. Hence, UV curing is a suitable technique to crosslink also filled coatings offering interesting properties for corrosion protection applications.
Wendel et al. (Wed,) studied this question.