Degradation of epoxy coatings under gamma irradiation
TypeArticles dans des revues 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.
Showing items related by title, author, creator and subject.
New insights in polymer-biofuels interaction Avancées dans la compréhension des interactions polymères-biocarburants RICHAUD, Emmanuel; DJOUANI, Fatma; FAYOLLE, Bruno; VERDU, Jacques; FLACONNECHE, Bruno (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 ...
ZAHRA, Yahya; DJOUANI, Fatma; FAYOLLE, Bruno; KUNTZ, M; VERDU, Jacques (ELSEVIER, 2014)tThe 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), ...
DJOUANI, Fatma; PATEL, Bhavesh; RICHAUD, Emmanuel; FAYOLLE, Bruno; VERDU, Jacques (Elsevier, 2012)This 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 ...
RICHAUD, Emmanuel; FAYOLLE, Bruno; VERDU, Jacques (Elsevier, 2011)This article deals with polypropylene stabilization by hindered 2,6-di-tert-butylphenols. Two aspects are mainly considered: the influence of stabilizer structure, of its concentration and temperature on induction period ...
RICHAUD, Emmanuel; FAYOLLE, Bruno; VERDU, Jacques (Woodhead Publishing Series - Elsevier, 2009)As soon as it appeared on the market, one half century ago, polypropylene (PP) appeared as a promising fibre-forming polymer but with some difficulties in processing due to a lack of control of its viscoelastic properties ...