Characterisation of Microcellular Foams using X-Ray Microtomography and Raman Spectroscopy

Closed cell polycarbonate foam is investigated using X-ray microtomography (XRMT). A specimen is prepared using the solid state processing route and a graded microstructure is obtained containing cell sizes from 10 to 90μm. The cell size distribution was estimated by modelling the foam dynamics and compared to a reconstructed geometry obtained from a XRMT experiment. The graded specimen contains regions with a microcellular structure. These regions are not suitable for XRMT investigations since the smallest details of the structure are below the resolution limit. An alternative approach for the characterisation of microcellular foams is suggested by using carbon nanotubes and Raman spectroscopy. A polycarbonate/carbon nanotube composite is molded and microcellularly foamed. Raman investigations verify that nanotubes are present within the structure and indicate straining of the nanotubes at intermediate steps during sample preparation and sample compression.