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Evaluation of crystalline polymer materials using a 2D-SAXS/WAXS system

Winter 2019 Volume 35, No. 1
09-16
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Yukiko Namatame and Keigo Nagao

In a crystal, atoms or molecules are arranged in a three-dimensional, repetitive pattern, and the properties of the crystal are determined by the chemical composition of the constituent atoms or molecules. The typical image of a crystal is a grain of a single crystal such as salt or alum, but many familiar materials, such as metals, ceramics, and crystalline polymers, are solids composed of microcrystals. These are called polycrystals, in contrast to single crystals. There are cases where the texture and crystallinity of the crystals constituting the material at larger scale are related to properties such as the strength and hardness of crystalline materials composed of a polycrystal.

Evaluation of crystalline polymer materials in powder X-ray diffraction is roughly divided into analysis of the small angle X-ray scattering (SAXS) region, corresponding to a long-period structure of about 1–100 nm, and analysis of the wide angle X-ray scattering (WAXS) region, corresponding to an atom-to-atom interval on the order of 0.1 nm (1 Å) . The fact that evaluation must be done by combining the SAXS and WAXS regions when considering the structure and properties of crystalline polymer materials is a point of difference from the evaluation of inorganic materials.

Cases have been reported, including in this journal, where measurement in the WAXS region was carried out via scanning with a 2D detector(1)–(3), but there are no reports of exposure measurement using transmission. This paper presents examples of analyzing polypropylene (PP), polyethylene (PE), and polybutylene terephthalate (PBT) with measurements carried out using the SmartLab fully-automated multipurpose X-ray diffractometer and the 2D-SAXS/WAXS transmission attachment.