Recent Developments in Polymer Characterization Using X-ray Diffraction

The acknowledged versatility of polymeric materials, which are widely used in the form of plastics, films, coatings and fibers, arises from the complex structural organization in these materials. X-ray diffraction (XRD) has long been successfully used to study various aspects of these structures in semicrystalline polymers, which includes thermoplastics, thermoplastic elastomers and liquid crystalline polymers. While many of the well established methods for the determination of molecular structure, evaluation of crystallinity and analysis of texture, continue to be improved to enhance the speed and precision of these measurements, new techniques are also being continually introduced. With the availability of intense X-ray sources, high-speed detectors and faster methods of analyzing the data, it is now possible to examine the structure at higher spatial resolution and smaller time scales. For instance, it is possible to follow development of structure in a processing line, such as in spinning and drawing operations, or in extrusion of films with a time resolution of less than one second [1–4], or examine the structural inhomogeneities that induced over distances of a few micrometers by the temperature and stress gradients that exist during processing [5–7]. These developments also permit combining XRD analysis with other characterization techniques such as thermal analysis [8], rheology, spectroscopy and microscopy [9]. We will discuss some of these developments that are useful in understanding the hierarchical structure and inhomogeneity in polymers, and the analyses of the 2-D data that are now commonly obtained during these measurements