Three-dimensional analysis of macroporosity distributions in polyolefin particles using X-ray microtomography

We applied X-ray microtomography (XMT) to determine the macroporosity distribution in polypropylene macroparticles extracted from a gas phase polymerisation process. Different specimens were scanned with a laboratory XMT setup comprising a microfocus X-ray source and an X-ray image intensifier. The XMT technique provides comprehensive three-dimensional (3D) data volumes representing the local X-ray attenuation in voxels of 5.3 µm × 5.3 µm × 5.3 µm size. In this paper we present the experimental methods and software tools to quantify the particles' local morphology parameters from such volume data. Therefore, after 3D image reconstruction with the Feldkamp algorithm the resulting volume data were processed with histogram based binarisation, connectivity check and volume rendering algorithms. From the resulting 3D images void size distributions in different radial regions of the particles were computed. This enables characterisation of the particles regarding their morphology and elucidation of the effect of given process conditions on morphogenesis.