Particle size distribution. Main definitions and measurement techniques

Abstract

The importance of the particle size distribution (PSD) of polymer latexes is first discussed; and definitions of differential / cumulative distributions and average diameters are presented. Main analytical techniques for latex PSD measurement are classified. Some ensemble techniques such as turbidimetry (T), elastic light scattering (ELS), and dynamic light scattering (DLS) are thorougly treated, and evaluated by considering the characterization of industrial latexes of unknown composition. The effect of uncertainties in the particle refractive index (PRI) on the PSD is also studied. A brief discussion on problems associated to the PSD measurement by standard electron microscopy (EM) is presented, together with the analysis of latex nanoparticles by atomic force microscopy (AFM), and the applicattion of new EM developments for the characterization of wet samples in their environment. Also, the principles of main fractionation techniques are briefly discussed, including sedimentation, unpacked/packed olumn chromatography, and field flow fractionation methods, together with an analysis of their detection systems, with emphasis on the estimation of the PSD ordinates from singlewavelength T measurements.