Degradation of epoxy coatings under gamma irradiation
Article dans une revue avec comité de lecture
Epoxy networks based on Diglycidyl ether of bisphenol A (DGEBA) and cured with Jeffamines (POPA) or polyamidoamine (PAA) were gamma irradiated at 25 1C in air. Dose rates of 50, 200 or 2000 Gy h- 1 for doses up 100 kGy were used. Structural changes were monitored by IR spectrophotometry, DSC and sol–gel analysis. Both networks display some common features: for I Z 200 Gy h- 1, reaction products grow proportionally to time and the rate is a decreasing function of dose rate. The simplest explanation is that peroxy radicals are the main precursors of these products (in the dose rate domain under study), through a unimolecular rearrangement of which an hypothetical mechanism is proposed. DGEBA–POPA are more reactive then DGEBA–PAA networks (according to IR criteria), that can be attributed to the high reactivity of tertiary CH bands in polyoxypropylene segments. The oxidation of these sites leads to methyl ketones. A simple kinetic model in which methyl ketones result from rearrangements of tertiary peroxyls and from tertiary alkoxyls was proposed. It leads to an expression of the radiochemical yield of methyl ketones (G(MK)) of the form GðMKÞ¼ a þ bI-1=2 where a and b are parameters depending of elementary rate constants. Experimental G(MK) values are reasonably well ﬁtted by this equation. In DGEBA–PAA networks, a wide variety of oxidation products, among which amides predominate, can be observed. In these networks, chain scissions predominate over crosslinking, whereas a slight predominance of crosslinking was observed, at least for the lowest dose rate, in DGEBA–POPA.
Cette publication figure dans le(s) laboratoire(s) suivant(s)
Visualiser des documents liés par titre, auteur, créateur et sujet.
Article dans une revue avec comité de lecturetThe thermo-oxidative behavior of unformulated (unfilled) samples of epoxy coatings has been studiedat five temperatures ranging from 70◦C to 150◦C. Two epoxy networks based on diglycidyl ether ofbisphenol A (DGEBA), ...
New insights in polymer-biofuels interaction Avancées dans la compréhension des interactions polymères-biocarburants Article dans une revue avec comité de lectureDJOUANI, Fatma; VERDU, Jacques; FLACONNECHE, Bruno; FAYOLLE, Bruno; RICHAUD, Emmanuel (Institut Français du Pétrole, 2015)This paper deals with polymer-fuel interaction focusing on specific effects of biofuels on polyethylene (PE) in automotive applications. The practical objective is to develop a predictable approach for durability of ...
Article dans une revue avec comité de lectureThe thermal oxidation behaviour of polyethylene films stabilized by various weight ratios of organophosphites (Irgafos 168) has been studied at selected temperatures. The duration of the induction period was found to ...
Article dans une revue avec comité de lectureThis work deals with a study of stabilizers loss by extraction in ethanol–cyclohexane mixtures simulating ethanol based biofuels. As theoretically predicted, cyclohexane has an extractive power considerably stronger than ...
Article dans une revue avec comité de lectureDegradation induced by thermal (50-110 °C) and radio-oxidation of low T g epoxy-amine networks has been studied. It has been found that oxidation leads mainly to amide groups formation at the vicinity of tertiary amines ...