Calculation of long periods in polymers and determination of the sizes of crystallites and amorphous regions

For the interpretation of long periods of oriented polymers, a calculation was carried out of scattering along the meridian of a small‐angle x‐ray texture diagram. In the calculation a scheme of the structure of a fibril was used, consisting of crystalline and amorphous regions. It was assumed that the crystallite center was statistically distributed along the fibril. The density distribution within a crystallite is given. For the interpretation of the experiment, several calibration graphs were obtained from theoretical curves. Wide‐ and small‐angle x‐ray diffractions were measured for a number of samples of polyethylene fibers and capron films. The sizes of crystallites and amorphous regions along the fibril axis were determined with calibration curves. These results are compared with the size of crystallites and crystallinity determined from wide‐angle diffraction and density.