Effect of SDS (sodium dodecyl sulphate) foam on polarised light characteristics

Abstract

Polarised light scattering experiments were conducted during the free drainage of SDS foams with three different bubble size distributions. Two types of completely polarised light were shone through the foam and all the five polarisation characteristic parameters (degree of polarisation P, degree of linear polarisation PL, degree of circular polarisation PC, orientation angle ψ and ellipticity angle χ) of the scattered light were determined to examine the changes of polarisation state. During the drainage process, the bubble size distributions of the foams remained almost constant, but with a decreasing liquid fraction. This process can be divided into three stages based on the rate of the decrease in liquid fraction. This study was focused on the static stage where the rate of change in liquid fraction reduced to nearly zero. It was found that four of the polarisation parameters, P, PL, PC and χ exhibit sensitivities to the liquid fraction and the bubble size distribution. ψ is largely independent of the liquid fraction and bubble size distribution, but shows a certain degree of correlation with the structural rearrangement of the polydispersed foams.