Determination of particle size in multiphase blends by different methods

Different methods for characterizing the morphology of multiphase blends we re applied to a blend of thermoplastic polyurethane with 20 wt% polypropyle ne as the dispersed phase. Optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AF M), and light scattering were compared. The microscopy methods were evaluat ed with respect to their suitability for quantitative image analysis for de termination of the particle size distribution. Comparison of the particle s ize distributions revealed that the dependence of the measured particle siz e on the method of preparation and technique was not very pronounced. The m ain difference resulted from cutting the particles outside their maximum di ameter. The measured particle sizes determined with methods that analyze th e whole particles, such as SEM on separated particles and laser light scatt ering, are larger than those measured on cut specimens. The factor 4/pi val id in monodisperse systems for the ratio between the real particle size and that measured on sections was found also to be applicable to this polydisp erse blend system. Although light microscopy requires the least preparation efforts, it is a reliable method for this blend system.