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|Type:||Artigo de periódico|
|Title:||Poly (ethylene terephthalate) thermo-mechanical and thermo-oxidative degradation mechanisms|
De Paoli, MA
|Abstract:||(1)H 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. (c) 2009 Elsevier Ltd. All rights reserved.|
|Editor:||Elsevier Sci Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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