Molecular and macromolecular structure changes in polyamide 11 during thermal oxidation
TypeArticles dans des revues avec comité de lecture
The present article reports a study of thermal oxidation of unstabilized polyamide 11 films at several temperatures (90–165 °C) under atmospheric pressure and under various oxygen pressures (up to 1.6 MPa) at 110 °C. The chemical structure changes are monitored by IR spectroscopy (carbonyl groups) and UV–visible spectrophotometry (yellowing). Molar mass changes are determined by size exclusion chromatography (SEC). By investigating the influence of oxygen pressure it is clearly shown that reactions involving P° radicals other than O2 addition cannot be neglected under atmospheric pressure. Under the conditions of this study limited to relatively low oxidation levels, IR and UV measurements indicate that carbonyl groups and chromophores responsible for yellowing have the same relative yield whatever the temperature and oxygen pressure. SEC measurements highlight the significant predominance of random chain scissions over crosslinking events. Crosslinking only appears after an induction time, presumably because it involves reactions between primary oxidation products. The ratio of carbonyl groups over chain scissions is about 7.5 at low conversion and about 2.5 at high conversion, showing that α amino alkoxy radicals are mainly transformed into imides without chain scission.
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RICHAUD, Emmanuel; OKAMBA-DIOGO, Octavie; FAYOLLE, Bruno; VERDU, Jacques; GUILMENT, Jean; FERNAGUT, François (Elsevier, 2013)The literature on oxidation kinetics of polyamides and model compounds has been reviewed in order to try to extract suitable information for non-empirical kinetic modeling. Polyamide characteristics are systematically ...
Molecular and macromolecular structure changes in polyamide 11 during thermal oxidation - Kinetic modeling OKAMBA-DIOGO, Octavie; RICHAUD, Emmanuel; VERDU, Jacques; FERNAGUT, François; GUILMENT, Jean; FAYOLLE, Bruno (Elsevier, 2015)The oxidation kinetics of unstabilized polyamide 11 thin ﬁlm under oxygen pressures up to 2.0 MPa was studied by means of ferrous ion method for hydroperoxides titration, size exclusion chromatography (SEC) for molar weight ...
OKAMBA-DIOGO, Octavie; RICHAUD, Emmanuel; VERDU, Jacques; FERNAGUT, François; GUILMENT, Jean; PERY, Frédérique; FAYOLLE, Bruno (Elsevier, 2016)Polyamide 11 ﬁlms stabilized by Irganox® 1098, Irganox® 1010 or Irganox® 245 were subjected to thermal oxidation at 110°C. The residual phenol content was assessed by comparing three analytical methods:high performance ...
OKAMBA-DIOGO, Octavie; RICHAUD, Emmanuel; VERDU, Jacques; FERNAGUT, François; GUILMENT, Jean; FAYOLLE, Bruno (Elsevier, 2016)Embrittlement processes occurring during thermal oxidation are investigated for stabilized and unstabilized polyamide 11 samples differing by their thicknesses and initial molar masses. Tensile tests were carried out in ...
OKAMBA-DIOGO, Octavie; FERNAGUT, François; GUILMENT, Jean; PERY, Frederique; FAYOLLE, Bruno; RICHAUD, Emmanuel (ELSEVIER, 2020)This paper addresses the effect of hindered phenols (mainly Irganox 1098 with a few comparisons with other phenolic antioxidants) on the stabilization of polyamide 11 aged at several temperatures (90–165 °C). The effect ...