Poly (ethylene terephthalate) thermo-mechanical and thermo-oxidative degradation mechanisms |
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Authors: | Wanderson Romã o,Yuri E. Corilo,Má rcia A.S. Spinacé |
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Affiliation: | a Laboratório de Polímeros e Reciclagem, Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154, 13084-971 Campinas, SP, Brazil b Laboratório ThoMSom de Espectrometria de Massas, Instituto de Química, Universidade Estadual de Campinas, 6154, 13084-971 Campinas, SP, Brazil |
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Abstract: | 1H NMR and MALDI-TOF MS measurements were used to study the thermo-mechanical and thermo-oxidative degradation mechanisms of bottle-grade PET (btg-PET). In the thermo-oxidative degradation, the concentration of low molar mass compounds increased with time and the main products were cyclic and linear di-acid oligomers. In the thermo-mechanical degradation, the main-chain scission reactions affect the stability of the cyclic oligomers. One of the most important bottle-grade PET co-monomers is diethylene glycol (DEG), which is a “reactive site” in the thermal degradation of btg-PET. The DEG co-monomer was shown to be the precursor to colour changes in btg-PET, owing to the attack by molecular oxygen on the methylenic protons adjacent to the ether oxygen atoms of DEG. This behaviour was observed in the thermo-oxidative degradation process in which the degradation of DEG causes the release of hydroxyl radicals in the polymeric matrix, thereby producing mono- and di-hydroxyl substituted species. This was also observed in the thermo-mechanical degradation process. |
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Keywords: | Poly(ethylene terephthalate) Thermo-oxidative degradation Thermo-mechanical degradation Diethylene glycol 1H NMR MALDI-TOF MS |
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