Effect of Size and Surface Modification of Nano Particles on the Performance of Epoxy Coatings

The exterior durability of epoxy coatings is poor as they tend to chalking and yellowing due to weathering under sunlight. Also, after prolonged exposure to sunlight, cracking of the coating takes place. This leads to the exposure of metal substrate to corrosive environment and thereby leading to extensive corrosion. That is why all epoxy coated components are top coated with acrylics or polyurethanes which is a costly process. Another alternative is to use UV absorbers like nano zinc oxide (ZnO) which is a well-known Ultra-Violet (UV) absorber is used in the current study. In this work, the effect of nano ZnO in the epoxy coatings on its weathering properties has been investigated. In addition to this, nano ZnO can also improve the mechanical properties and corrosion resistance without affecting the optical clarity of clear epoxy coats. Nano ZnO powder was functionalized with 3-glycidyloxypropyl-trimethoxysilane (GPTMS) and incorporated into the clear epoxy resin its effect on performance, mechanical and optical properties of the coating. The results were compared with unmodified nano ZnO particles. Ultra-Violet weathering tests were done to study their weathering properties. Electro chemical impedance spectroscopy (EIS) was used for studying corrosion properties and mechanical tests like taber abrasion, pull-off adhesion and hardness tests were carried to evaluate the mechanical properties.