Novel image analysis of two-dimensional X-ray fiber diffraction patterns: example of a polypropylene fiber drawing study

On-line studies of the structural development during continuous drawing of a polypropylene fiber were carried out using synchrotron wide-angle X-ray diffraction. A unique image analysis method was introduced to extract quantitative information on the crystal, amorphous and mesomorphic fractions. In addition, the unit-cell parameters and the crystal orientation were obtained under various draw conditions. It was found that the mesophase remained about constant during drawing. At draw ratios less than 6.0, the crystallinity increased and the crystal density decreased as a result of the stress-induced crystallization of crystals with a large degree of disordering. At draw ratios above 6.0, the crystallinity increased slowly and the decrease in crystal density was also retarded because of the draw-induced melting. The crystal orientation increased with increasing draw ratio up to a ratio of 6.0 and then decreased, probably because of chain breakage.