Preparation and characterization of composite coatings containing a quaternary ammonium salt as an anti-static agent

The main aim of the present study is to manufacture antistatic sheets with high transparency and high electrical conductivity by dip coating. Here, we used coating solutions consisting of a quaternary ammonium salt, a urethane acrylate oligomer, a photoinitiator, and a mixture of solvents which contains a water-soluble high boiling solvent of monobutyl glycol ether, 2-butoxyethanol. The coating solutions were deposited on polymethyl methacrylate (PMMA) substrates, which were subjected to a two-step drying process at 23 °C and at 60 °C, and subsequently cured by ultraviolet radiation. We have examined the effect of the concentration of the water-soluble monobutyl glycol ether, relative humidity (RH) at the first step, and drying time on the electrical conductivity, contact angle, and optical transmittance and haze of the coated layers. The surface electrical resistivity (ρ_s) monotonically decreased with the concentration of the monobutyl glycol ether, RH, and drying time. The water contact angle of the surface of the coated layers increased with decrease in ρ_s. These results strongly suggest a migration and fixation of the quaternary ammonium salt at the air/layer interface during the drying process. The coated PMMA sheet prepared under the optimal condition showed fairly good performance in terms of the optical and electrical properties.