Polymer Differentiation with Computed Tomography: Opportunities and Limitations

A specimen consisting of six stacked polymer sheets, each approximately 500 μm thick, was prepared for analysis. The polymers included polypropylene (PP), polyethylene (PE), polystyrene (PS), polyamide (PA), polyetheretherketone (PEEK) and polyethylene terephthalate (PET). Two different CT devices were employed: the GE Nanotom 180NF and the RX Solutions Easytom 160, each with specific parameters and varying voltage settings. Additionally, simulations using the inhouse software SimCT were conducted to complement the experimental data, focusing on both polychromatic and monochromatic X-rays. The grey values obtained from scans as well as simulations were analyzed to determine the distinguishability of the polymers based on their attenuation properties. It is shown that a grey-value based differentiation is possible if the polymers show significant differences concerning density and / or elemental composition. Furthermore, contrast enhancement by reduction of voltage, energy and noise leads to higher contrast between different polymer classes.