Study of the Degradation of an Epoxy/Amine Resin, 1

Abstract

Summary: The degradation of an epoxy/amine resin was studied under photolytic conditions in absence and in presence of oxygen and under thermooxidative conditions. The resin is obtained after curing the diglycidyl ether of bisphenol‐A (DGEBA) with a poly(propylene glycol) which is diamine terminated. The mechanisms of degradation of the two separate components before curing were also investigated. Analysis by IR and UV‐Vis spectroscopies revealed that the oxidation photoproducts detected during the degradation of the epoxy/amine result from the oxidation of the DGEBA part, of the amine crosslinks and, to a lower extent, of the poly(oxypropylene) units. Their mechanism of formation essentially involves chain scission reactions. During irradiation, the yellowing observed is mainly due to the formation of a quinone methide structure. Thermooxidation generates high discoloration with some products only generated in that case. For all experiments, a detailed analysis of the IR spectra is given with the chemical mechanisms of formation of the degradation products.ATR‐IR spectra of an epoxy/amine sample in the carbonyl region during photooxidation.magnified imageATR‐IR spectra of an epoxy/amine sample in the carbonyl region during photooxidation.

Model-based analysis of photoinitiated coating degradation under artificial exposure conditions

“…Rivaton et al state that the observed profile has to be mainly attributed to limited oxygen diffusion, but also partly to absorption by photoproducts. Similarly, Mailhot et al 52,53 have found a photooxidation profile that reaches 300 lm into an epoxy-amine coating. In this case the cured resin had a glass transition temperature of only À50°C.…”

“…The relationship between the dimensionless concentration of elastically effective network chains (y CC ) and the loss of benzene rings is unknown, but it seems possible that a 40% decrease in the crosslink density at the surface can lead to a reduction of 80% in the benzene concentration in the surface layer. For soft epoxy systems, Mailhot et al 53 have found an almost complete loss of aromatic character in the surface layer. In Fig.…”

“…Equilibrium water absorption and oxygen solubility could also be different. It is not known how these changes will influence the rate of oxygen diffusion, but Mailhot et al 52,53 have found that some oxidation products can be in liquid or solid form and be likely to generate a viscous layer, the properties of which are unknown. Rivaton et al 55 even measured an almost 40% decrease in the rate of oxygen permeability after only 10 h UV radiation exposure.…”

Effect of Ultraviolet Absorber on Photo-Degradation of Epoxy Coating Studied by Slow Positron Beam

“…The growth of the polar groups can reduce the S parameter in large scale. On the other hand, UV irradiation induces chain scission reactions on coating surface, resulting in the formation of hydroxyl radicals [17]. Residual radicals, which are not consumed by oxygen in air, will reduce the formation of Ps, then contributing to a lower S parameter.…”

Effect of ultraviolet light irradiation period on bond strengths between fiber-reinforced composite post and core build-up composite resin

“…The silane coupling treatment can establish chemical bonding between the fiberglass of the FRC post and the core build-up materials. Plasma and UV irradiation are considered to clean surfaces by removing the organic contamination 11,15,16) , increasing the surface microroughness [16][17][18][19] , and changing the molecular structure of the surface area [16][17][18][19][20] . If the molecular structure of the matrix resin is changed, it is possible to create IPN bonding despite the thermoplastic polymers.…”