Measurement of Degree of Crystallinitty of Polymer by
X-ray Diffraction Analysis



The degree of the crystallinity of crystalline polymer is a structural parameter that has much to do with their physical properties in general. An evaluation of the degree of crystallinity sometimes enables you to identify the causes of insufficient rigidity, cracks, whitening and other defects.
The methods for measuring the degree of crystallinity include the density, thermal analysis, NMR and IR methods.
An explanation will be given here of the method for measuring the degree of crystallinity by the X-ray diffraction technique that makes it possible to make the measurement with the microcrystals 1mm or so in diameter left in the solid state as they are.

Example of measurement by the wide angle X-ray diffraction method

In the X-ray diffraction analysis, a sample is irradiated by X-rays. From the diffraction information thus obtained (wide angle X-ray diffraction patterns or wide angle X-ray diffraction profiles), the diffused regions are divided into those derived from noncrystals and those derived from crystals. Then, the degree of crystallinity is calculated as a ratio of crystal-derived scattering intensity to total scattering intensity

Normally, a multi-peak separation program is used to separate the crystal and noncrystal regions.
Further, the setting of the noncrystal region depends on a noncrystal model.

As a detailed method for analyzing the degree of crystallinity, there is a method described in the publication of W. Ruland* to be followed that exclude incoherent scattering and take account of thermal oscillation and disturbance in crystals. However, a short-cut version of this method is commonly used because there is generally much demand for the evaluation of a relative degree of crystallinity and such short-cut version provides an easy and quick method for making calculations with good reproducibility.
* W.Ruland, Acta Cryst.,14, 1180 (1961)

Example of measurement by the wide angle X-ray diffraction method

Search Number 1021

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