X-ray ultramicroscopy: A new method for observation and measurement of filler dispersion in thermoplastic composites

A phase contrast X-ray imaging technique has been developed to observe and determine filler distribution in polymer composites, providing greatly enhanced 2-D image quality over conventional methods such as scanning electron microscopy (SEM). High spatial resolution X-ray ultramicroscopy (XuM) was developed and employed for this work. This method provides a clear visualization of filler dispersion patterns in polypropylene and nylon 6 matrices even with a sample thickness of up to 200 μm. Quantitative analysis of the filler dispersion quality derived from the 2-D images was carried out using a commercially available image analysis software. The X-ray phase contrast imaging and micro-tomography results presented in this paper demonstrate the viability of these techniques for qualitative and quantitative characterizations of filler distribution in thermoplastic composites. This technique offers several advantages over existing imaging methods because it avoids tedious sample preparation, yields well contrasted image enabling more accurate quantification of composite microstructure, and provides 2-D and 3-D information on filler distribution in polymer composites.