In-situ monitoring by fibre-optic NIR spectroscopy and rheometry of maleic anhydride grafting to polypropylene in a laboratory scale reactive extruder |
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Authors: | Lalehvash Moghaddam Llewellyn RintoulPeter J Halley Graeme A GeorgePeter M Fredericks |
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Institution: | a Chemistry, Faculty of Science and Technology, Queensland University of Technology, GPO Box 2434, Brisbane Qld 4001, Australia b Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Qld 4072, Australia c School of Chemical Engineering, The University of Queensland, Qld 4072, Australia d Centre for Tropical Crops and Biocommodities, Queensland University of Technology, GPO Box 2434, Brisbane Qld 4001, Australia |
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Abstract: | The graft copolymerisation of maleic anhydride (MAH) onto polypropylene (PP) has been studied in situ by interfacing a laboratory scale mini-extruder/processor with a near-infrared (NIR) spectrometer via a fibre optic link. Apparent viscosity was measured simultaneously with the NIR spectra. The graft reaction was carried out at several temperatures with and without the initiator, dicumyl peroxide (DCP). Analysis of the NIR spectra showed the reaction to be first order with respect to MAH, and that the graft reaction rate was not affected by the presence of DCP. However, DCP caused a large increase in chain scission reactions leading to a dramatic drop in apparent viscosity. In the absence of DCP, scission reactions occurred at a slower rate and the apparent viscosity remained steady, after an initial drop, for about 15 min during the early part of the reaction. We suggest that a possible explanation for this might be a “repair mechanism” involving the reaction of two PP macro-radicals with a single MAH moiety, thus maintaining the molecular weight. Once the concentration of MAH drops, this reaction becomes less significant and scission reactions dominate. |
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Keywords: | Graft polymerisation Reactive extrusion Maleic anhydride Polypropylene NIR spectroscopy |
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