J. Synchrotron Rad. (1997). 4, 223-227 Investigation of the Variation in Orientation and Crystallinity in Poly(ethylene terephthalate) Containers Using Microfocus X-ray Diffraction C. Martin, a A. Mahendrasingam, a W. Fuller, ~ J. L. Harvie, b D. J. Blundell, c J. Whitehead, c R. J. Oldman, c C. Riekel a and P. Engstr6m a aDepartment of Physics, Keele University, Keele, Staffordshire ST5 5BG, UK, blCI Polyesters, PO Box 90, Wilton, Middlesbrough, Cleveland TS90 8JE, UK, clCI Wilton Research and Technology Centre, PO Box 90, Wilton, Middlesbrough, Cleveland TS90 8JE, UK, and dESRF, BP 220, F-38043 Grenoble CEDEX, France. E-mail: pha40 @ keele, ac. uk (Received 6 February 1997;accepted20 March 1997) The microfocus X-ray beamline at the European Synchrotron Radiation Facility has been used to investigate the variation in molecular orientation and crystallinity in the wall of a container fabricated from poly(ethylene terephthalate). Two-dimensional wide-angle X-ray scattering patterns were recorded and displayed in real time as the specimen was tracked across the incident X-ray beam enabling the measurement of textural changes to be made with a spatial resolution of ,~ 2 lam. Keywords: PET; X-ray diffraction; microfocus; orientation; crystallinity; wide-angle scattering; CCD detectors. 223 1. Introduction We have recently reported the use of microfocus instru- mentation on beamline ID13 at the European Synchrotron Radiation Facility to investigate the variation in poly- mer orientation and crystallinity in spherulites of the optically active thermoplastic homopolymer poly-D-(-)- 3-hydroxybutyrate (Mahendrasingam et al., 1995). In these studies the diameter of the X-ray beam at the specimen was ~101am and this spatial resolution was sufficient to show that the crystallites in the specimen were systematically oriented so that the a axis in each crystallite was oriented parallel to a radius of the spherulite but with the degree of orientation and crystallinity decreasing towards the centre of the spherulite. Using similar techniques, local variations in polymer chain orientation have been described in injection-moulded liquid-crystalline polymers (Dreher, Zachmann, Riekel & Engstrrm, 1995). Physical properties, such as strength and gas-transport properties, of artefacts fabricated from poly(ethylene terephthalate) (PET) depend on the degree of polymer orientation and crystallinity and its variation in the artefact. In an effort to improve the efficiency and quality control in the processing of bulk polymers in the manufacture of products such as containers from PET (which have a high performance specification), we have undertaken a preliminary study of the dependence of polymer orientation and crystallinity on fabrication conditions. This report describes experiments where the microscopic variation of these characteristics is studied with a resolution of ,~ 2 lxm within the wall of such a container. © 1997 International Union of Crystallography Printed in Great Britain - all rights reserved The manufacture of PET containers involves first the injection moulding of an unoriented amorphous preform followed by blowing the preform into a cold shaped mould to form the container. Often this process is carried out via a two-stage route in which the preform is first cooled to room temperature and is then subsequently reheated for the blowing stage. However, the container used for this investigation was formed by the alternate one-stage route where the hot preform is moved to a conditioning zone in order to cool to the blowing temperature before moving to the blowing zone. In both these manufacturing routes there is a significant variation in the temperature profile through the wall of the preform at the moment of extension in the blowing zone. During blowing, the inner surface of the preform is cooled by the expansion of the compressed air used for inflation, the outer surface is cooled by contact with the (relatively) cold mould whilst the internal thermal energy is raised by strain heating. In addition, the contour shape of the container and the complex blowing process itself produces considerable variation in wall thickness and direction of stretching at different positions in the container. The polymer therefore experiences a wide variation in draw temperature, draw ratio and draw direction at different positions of the container and at different depths in the wall, resulting in a wide variation of orientation and crystallinity in the local polymer structure. In order to understand the mechanical properties of the container it is necessary to be able to characterize how this structure can vary. One of the main difficulties of this characterization, and the reason for undertaking this investigation, is the difficulty of probing variations in structure through the container wall Journal of Synchrotron Radiation ISSN 0909-0495 © 1997