Impact of spray-casting height and pressure on durability and superhydrophobicity of nanocomposite coatings

Y.H. Yeong, A. Davis, A. Steele, E. Loth, I. Bayer, G. De Combarieu
Mechanical & Aerospace Engineering, University of Virginia, US

Keywords: spray-casting, spray-cast height and pressure, superhydrophobic, nanocomposite, durability


Recently, researchers introduced a new technique to fabricate superhydrophobic coatings by spray-casting polymer-nanoparticle suspensions using an air-atomizing nozzle. Upon thermosetting, the deposited polymer networks crosslink to form a durable, superhydrophobic nanocomposite coating. However, while the mechanisms for the formation of superhydrophobic nanocomposites by spray atomization have been documented, questions remain on the effects of spray-cast deposition height and pressure on the superhydrophobic performance of the coating. Understanding these effects is critical for large-scale manufacturing applications which use automated robotic spray systems. To address these questions, a polymer-nanoparticle suspension was spray-casted on aluminum substrates placed on a motor-driven traverse table. Consistency in the spray coating process was maintained by translating the substrate in controlled longitudinal and lateral motions while the spray deposition height and pressure was varied. The superhydrophobic performance of the resulting nanocomposite coating was determined via contact and roll-off angle measurements. Results (Fig. 1) showed an increase in superhydrophobicity (increase of 10 degree CA & decrease of 10 degree ROA) as spray height was increased from 3 to 8 inches. An increase in superhydrophobic performance was also observed when air-atomizing pressures were reduced from 40psi to 15psi.