J. Appl. Cryst. (2000). 33, 1031±1036 Shaofeng Ran et al.  Novel image analysis 1031 research papers Journal of Applied Crystallography ISSN 0021-8898 Received 17 September 1999 Accepted 4 April 2000 # 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved Novel image analysis of two-dimensional X-ray fiber diffraction patterns: example of a polypropylene fiber drawing study Shaofeng Ran, a Xinhua Zong, a Dufei Fang, a Benjamin S. Hsiao, a * Benjamin Chu a * and Roger Ross b a Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA, and b DuPont Nylon, Chattanooga, TN 37415, USA. Correspondence e-mail: bchu@notes.cc.sunysb.edu On-line studies of the structural development during continuous drawing of a polypropylene ®ber 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. 1. Introduction Small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) are routine methods for characterizing the structure and morphology of oriented polymers such as ®bers and ®lms (Statton, 1964; Glatter & Kratky, 1982; Balta- Calleja & Vonk, 1989; Alexander, 1969). A proper study of SAXS and WAXD during ®ber drawing requires the use of a two-dimensional detector system (Mills et al. , 1985) so that the structural information on the anisotropic nature of the system can be extracted from the two-dimensional patterns. The coexistence of both sharp and diffuse diffraction features in a WAXD pattern is usually considered as evidence for the two-phase morphology, which consists of perfect crystalline domains interspersed with random amorphous regions. However, this simpli®ed view cannot be used to explain several recent experimental observations of polymer ®bers (Androsch et al., 1999; Androsch & Wunderlich, 1998; Wunderlich, 1997). These ®ndings suggest that the ®ber structure should include an intermediate `phase' between the crystalline and amorphous fractions, which may arise from lattice dislocations of one- or two-dimensional ordering in the crystal phase or the oriented amorphous chains. Thus the intermediate phase (mesophase) represents a state of order between the zero long-range ordering (amorphous state) and the three-dimensional crystalline ordering. The mesophase has been reported in many polymer ®bers, such as poly- propylene, Kevlar and nylon 66. It is thought that the nature of the mesophase can affect the macroscopic mechanical prop- erties, at least in polypropylene (Phillips & Wolkowicz, 1996), and is, therefore, of practical importance. The mesophase in isotactic polypropylene (iPP) was pointed out ®rst by Natta et al. in 1959 (Bruckner et al., 1991) and has been studied extensively since then (Hendra et al., 1984; Corradini et al., 1986, 1989). However, no effective method that is able to extract quantitative information on the mesophase exists. In this study, we introduce a unique image analysis method to extract structural and morphological information from the two-dimensional WAXD patterns, using iPP as a model system. The fractions of crystal, mesomorphic and amorphous phases as well as other structural parameters can be obtained from this analysis, which is also applicable to other polymeric ®bers. 2. Experimental The polypropylene ®ber was produced from a commercial Ziegler±Natta resin with M w of 3.25  10 5 g mol 1 and M w /M n of 5.6. This ®ber contained an organic blue pigment, which also acted as a nucleating agent. Synchrotron measurements were carried out at the State University of New York (SUNY) X3A2 beamline in the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory (BNL). The wavelength used was 1.544 A Ê . A three-pinhole collimator system (Chu et al., 1994) was used to reduce the beam size to 0.6 mm in diameter. The two-dimensional detector for WAXD measurements was a Mar CCD X-ray detector (Mar, USA). The distance between