In a previous paper, the usefulness of SEM image analysis for the characterization of the size and shape of Ziegler-type quasi-spherical catalyst particles and polypropylene particles was shown. In the present paper, the method is extended to silica-supported and unsupported catalysts for ethylene polymerization. The shapes of these catalysts are more or less remote from a sphere. It was shown that the selected circularity index allows us to distinguish between spherical, polyhedric and more complex shapes. However, the sampling for SEM examination is more difficult the more remote the particles are from spheres. Moreover, the digitization on 512 x 512 pixels -- necessary for non-spherical particles -- leads to a four-fold increase in computer time. As far as the determination of the 'true' dispersion of a catalyst particle batch is concerned, it is not possible to obtain it from a single sample. One very interesting result is the shape evolution between silica-supported catalysts and the corresponding prepolymers.
Посилання на статтю:
SEM image analysis to characterize the shape of catalyst and polyethylene prepolymer particles in olefinic polymerization / R. Hagege* and the late J. C. Baillyt // Polymer. – 1993. – Vol 34. – P. 2720-2725.