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Investigation of polypropylene degradation during melt processing using a profluorescent nitroxide probe: A laboratory-scale study |
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| Authors: | Laleh MoghaddamJames P Blinco John M ColwellPeter J Halley Steven E Bottle Peter M FredericksGraeme A George |
| Affiliation: | a Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia b ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia c Defence Materials Technology Centre, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, QLD 4072, Australia d Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia |
| Abstract: | Degradation of polypropylene (PP) during melt processing was studied using a novel profluorescence technique. The profluorescent nitroxide probe, 1,1,3,3-tetramethyldibenzoe,g]isoindolin-2-yloxyl (TMDBIO) was added to PP during melt processing to act as a sensor for carbon-centred radicals. Trapping of carbon-centred radicals, formed during degradation of PP, led to an increase in fluorescence emission from TMDBIO adducts. Through analysis of viscosity changes during processing cumulative chain scission degradation was estimated. At processing temperatures of 210 °C or below, fluorescence emission from TMDBIO adducts could be correlated with cumulative chain scissions when the number of chain scissions was small. At higher temperatures, a correlation was not observed most probably due to radical-trap instability rather than decomposition of the TMDBIO. Thus, TMDBIO may be used as a profluorescent sensor for degradation of PP during melt processing when the processing temperature is 210 °C or below. |
| Keywords: | Profluorescent nitroxide Polypropylene Extrusion Degradation Chain scission |
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