A novel methodology to estimate the particle size distribution of latex using relative measurements of elastic light scattering and turbidimetry

Abstract

In a previous publication, turbidimetry and elastic light scattering (ELS) were shown to be two techniques that, combined, can be used to determine particle size distributions (PSDs) of suspended particles. The proposed method, consisting in the solution of a linear inverse problem, was based on the assumption that absolute measurements of both turbidimetry and ELS were available. However, such measurements are normally difficult to obtain in practice, whereas relative measurements can be easily made. The technique proposed in this paper relaxes the assumption of absolute measurements by including an unknown parameter in the combined model. In this form the inverse problem to be solved under the new assumptions becomes a non-linear one. Since the problem can be solved semi-analytically, in all cases the results are exact and not linked to issues such as lack of convergence or other similar types of complications sometimes encountered in purely numerical solutions. Three synthetic examples of PSD estimation of polymer latex are used to show how the proposed methodology works in practice. The approach proposed here avoids the use of any type of calibration of the instruments used to measure turbidity and ELS, and makes the technique based on the combination of these two measurements a more powerful alternative than it was before. Copyright © 2000 John Wiley & Sons, Ltd.