ABSTRACT

Motivated by the need to improve spray coating transfer efficiencies, results are presented from an experimental investigation into the interaction between an air-blast spray and a high-speed moving surface. Three model elastic liquids of varying polymer molecular weight and three inelastic liquids of varying shear viscosity were used to isolate the effect of elasticity and shear viscosity, respectively, on spray impaction behavior. In addition, an industrial liquid friction modifier, KELTRACK^TM , for use in the railroad industry, was included in the spray tests. High-speed photography was used to examine spray impingement. Ligaments, formed as a consequence of a liquid's viscoelasticity, were observed impacting the surface for the higher molecular weight elastic liquids. The effect of increasing elasticity was shown to increase spray coating transfer efficiencies; this is attributed to a larger proportion of the sprayed liquid reaching the target surface as well as an increased splash threshold on impact. Observations and recommendations were stated regarding transfer efficiency improvement considerations.