Effect of process parameters on droplet spreading behaviour over porous surface

Droplet spreading behaviour over a porous surface is a complex phenomenon, and is a basic component of many industrial processes, for example the spray coating process. The coating process has wide applications and this includes coating of urea fertilizer to produce slow release urea. The quality of coating film in such applications is affected by many factors, one of them being droplet spreading on the substrate. Droplet spreading behaviour is affected by process parameters such as viscosity, density, surface tension, impact velocity, porosity, etc. Droplet spreading on a porous surface involves penetration into the porous surface and spreading on the surface. Previously, the effect of individual process parameters has been studied. The current work aims at finding the interactive effect of process parameters on droplet spreading behaviour by using response surface methodology. The combined effect of liquid viscosity, impact velocity, and surface porosity has been studied on contact angle, spreading factor, and residual drop volume. The results show that minimum contact angle can be achieved with maximum impact velocity, minimum porosity, and minimal liquid viscosity. Similar behaviour was observed with droplet residual volume. Maximum spreading factor was attained at minimum viscosity and porosity while impact velocity was at maximum level.