A Study of Oil Drop Roll Up on a Solid Substrate

in Surfactant Solution: Theory and Experiments

Sandip Roy

Department of Chemical Engineering, Indian Institute of Technology, Bombay

India 400 076

Sept 27 2005, 5 pm A102/A206, UICT

Abstract

The removal of oily soils from solid substrates during detergency occurs through a combination of roll up, emulsification and solubilzation. Depending on the nature of the three phase oil-water-solid interface, the surfactant concentration and the drop size, either the drop can roll up partially, or can detach completely from the substrate. The roll up process is modeled by combining a modified from of the well-known Young equation with the solution of the Navier-Stokes equation for predicting the radial velocity of the movement of the three-phase interface. The model allows prediction of the transient drop diameter and height during the roll up process. Experimental results are also reported for the system comprised of a model oily soil (n-hexadecane) droplet which undergoes roll up on glass substrate upon the addition of a solution of sodium dodecyl sulfate (SDS) solution. The experimental results on variation of contact angle, drop height and contact diameter of oil-glass interface at with time during roll up match well with those predicted by the model.