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Photooxidative Degradation and Conformational Changes in Syndiotactic Polypropylene/Clay Nanocomposites

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Abstract:

Syndiotactic polypropylene nanocomposites based on layered silicates in various proportions were subjected to prolonged (246 h) ultraviolet (UV)-c irradiation. Fourier transform infrared (FT-IR) spectroscopy was used in order to investigate the molecular alterations of the polymeric matrix during the UV exposure relative to the concentration of nanoclay. It was found that a significant increase of the helical conformation upon the irradiation took place as a result of scissions of the polymeric chains. In addition, a simultaneous increase in the crystallinity was verified by X-ray diffraction (XRD) measurements. Furthermore, a variety of photooxidation products were detected, among them carboxylic acids, ketones, γ-lactones, and esters. We report in this paper the impact of the clay on the degradation mechanism of syndiotactic polypropylene mostly by the production of additional free radicals. Therefore, the relative intensities of the produced photooxidative species are affected drastically as a function of the concentration of the layered silicate present. Finally, an interaction of the carbonyl groups formed in the polymer upon irradiation with the polar groups of the layered silicates was confirmed both from infrared and UV-visible spectroscopic studies.

Keywords: DEGRADATION; FOURIER TRANSFORM INFRARED SPECTROSCOPY; FT-IR SPECTROSCOPY; NANOCOMPOSITES; SYNDIOTACTIC POLYPROPYLENE

Document Type: Research Article

DOI: http://dx.doi.org/10.1366/000370206778999003

Affiliations: 1: Foundation for Research and Technology-Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH-ICEHT) P.O. Box 1414, Stadiou Str., Patras, 26504 Greece 2: Department of Material Science, University of Patras, 26500 Patras, Greece 3: PANalytical Inc., Regional Business Center, 12 Michigan Drive, Natick, Massachusetts 01760

Publication date: November 1, 2006

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