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Published March 2008 | Published
Journal Article Open

Simultaneous birefringence, small- and wide-angle X-ray scattering to detect precursors and characterize morphology development during flow-induced crystallization of polymers

Abstract

An experimental configuration that combines the powerful capabilities of a short-term shearing apparatus with simultaneous optical and X-ray scattering techniques is demonstrated, connecting the earliest events that occur during shear-induced crystallization of a polymer melt with the subsequent kinetics and morphology development. Oriented precursors are at the heart of the great effects that flow can produce on polymer crystallization (strongly enhanced kinetics and formation of highly oriented crystallites), and their creation is highly dependent on material properties and the level of stress applied. The sensitivity of rheo-optics enables the detection of these dilute shear-induced precursors as they form during flow, before X-ray techniques are able to reveal them. Then, as crystallization occurs from these precursors, X-ray scattering allows detailed quantification of the characteristics and kinetics of growth of the crystallites nucleated by the flow-induced precursors. This simultaneous combination of techniques allows unambiguous correlation between the early events that occur during shear and the evolution of crystallization after flow has stopped, eliminating uncertainties that result from the extreme sensitivity of flow-induced crystallization to small changes in the imposed stress and the material. Experimental data on a bimodal blend of isotactic polypropylenes are presented.

Additional Information

© 2008 International Union of Crystallography. Received 30 April 2007; Accepted 23 January 2008. This work was funded by the National Science Foundation under awards DMR-0080065 and DMR-0505393. The authors are grateful to Dr Jan Verhoeven (Amolf) for providing the Al-coated mica mirrors. We acknowledge the European Synchrotron Radiation Facility and the Netherlands Organization for Scientific Research for provision of synchrotron radiation facilities, and all DUBBLE staff for assistance during experiments. Mr B. Vrolijk of Element 6 is thanked for advice on how to mount the diamond windows. FA and FJBC wish to acknowledge the 'Ministerio de Educación y Ciencia' (grant FIS2004-01331), Spain, for financial support. LFB wishes to acknowledge the 'la Caixa' fellowship program.

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August 22, 2023
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