INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
capítulos de libros
Título:
Improved Estimation of the Particle Size Distribution from Combined Light Scattering Measurements
Autor/es:
VEGA, J. R.; GUGLIOTTA, L. M.; CLEMENTI, L. A.
Libro:
Measurement of Particle Size Distribution of Polymer Latexes
Editorial:
Signpost Research
Referencias:
Lugar: Kerala, India; Año: 2009; p. 91 - 127
Resumen:
Light scattering (LS) techniques, such as single-angledynamic light scattering (DLS), elastic light scattering (ELS), andturbidimetry (T), are frequently used to estimate the particlesize distribution (PSD) of a polymeric colloid. Irrespective of theutilized technique, the acquired measurements have lowinformation content on the PSD, and an ill-conditioned numericalinverse problem must be solved. As a consequence, only a lowresolution estimate of the PSD can be obtained. However, the PSDresolution can be improved by combining 2 or more sets ofindependent measurements in a single inverse problem, providedthat the latex exhibits an adequate stability to keep invariant itsPSD along all the measurements. The improvement of the PSDresolution is due not only to the larger information content onthe PSD but also to a better conditioning of the combinedinverse problem. Several combined LS techniques are analyzed:multiangle DLS (MDLS), MDLS+ELS, T+ELS, and MDLS+T. The mathematical model corresponding to a generic combined problem is presented. In general, such combined problem is nonlinear, because it involves the simultaneousestimation of the PSD and of at least a multiplicative unknown ‘normalization’parameter. However, in some cases, the nonlinear problem can be transformed intoa linear one. A simulated example corresponding to a bimodal PSD is investigatedthrough different combined measurements. Two experimental cases are also discussed: an industrial latex of unknown particle refractive index, and a bimodal polystyrene latex prepared by mixing 2 narrow standards. It is proved that combined techniques are more useful than single optical techniques for estimating reliable PSD of latexes.