Methods for Characterizing the 3-D Morphology of Polymer Composites

3-dimensional visualization of polymer morphology is of increasing interest in the polymer community because it provides a deeper insight into the arrangement of the phases in heterophasic polymeric materials, for example in composites. Depending on the size of the fillers, an adequate method offering a good compromise between suitable resolution and observable volume must be selected. Different polypropylene composites filled with long glass fibres, mica and talcum particles were investigated. Four methods were applied to account for the different filler sizes. For composites containing fillers larger than several micrometers, i.e. glass fibres and mica particles, X-ray tomography offers a very good combination of visibility and volume. Serial sectioning by polishing in combination with light optical microscopy can be an alternative if no X-ray equipment is available. This combined method has the disadvantage, however, that the imaged volume is smaller and involves more effort, which makes it unsuitable for routine observations. The much smaller talcum particles with thicknesses down to 200 nm were investigated by coupling focused ion beam (FIB) milling and scanning electron microscopy (SEM) and by insitu ultramicrotomy in the SEM. Both methods led to good and comparable results.