Some parameters measured by XRD can be used to characterize the mechanical and thermal properties of polymers, making XRD a commonly used characterization method in the field of polymers.
1.XRD measurement of crystallinity
The principle of XRD determination of crystallinity is to make use of the different contributions of the crystalline and non-crystalline regions in the polymer to X-ray diffraction, and the diffraction peak measured on the diffraction photograph is decomposed into two parts: crystallization peak and non-crystallization peak, and crystallinity is the ratio of crystallization peak and total peak area.
2. Determination of fiber orientation
XRD can also determine the orientation of the fiber. When the grain plane is perpendicular to the fiber axis, the reflection point can not be obtained on the X-ray diffraction pattern, but only when the grain plane is at a certain Angle to the X-ray direction. Because randomly oriented polymers have grains in all directions, the diffraction pattern appears to be closed concentric circles.
X-ray diffraction rings in different states
3. Grain size
The grain size of polymer has an effect on the mechanical properties and transparency of macroscopic materials, and it is one of the indexes of material morphology and structure. Since the crystal region size of the polymer material is much less than 10μm (nanometer scale), it can be known that the diffraction peak is significantly widened, and then the grain size can be determined only by calculating the widening.