Infra-red study of hydrogen bonding in amine-crosslinked epoxies

A discussion of the molecular mechanisms of moisture transport in epoxy resins

“….OH hydrogen bond between two hydroxyls. Evidence for each of these bonds exists, 19,20 although it is difficult to ascertain the relative extent to which each type will be present. Although the bonds are illustrated here in the intramolecular sense (between covalent closest pairs), it is possible for similar bonds to occur between nonbonded neighbors, creating a more intermolecular hydrogen bond (although in the strict sense a distinction between intramolecular and intermolecular is ambiguous in a crosslinked network).…”

“…These vibrations are hindered by the formation of hydrogen bonds, resulting in an absorbance peak in the 3600 -3200 cm Ϫ1 range. 19,20 The exact nature of the hydrogen bonding is very complex and depends on factors such as the nucleophilicity of the amines, the distances between the polar species, and the presence of steric hindrances.…”

“…However, the two effects are not independent of each other, as is illustrated with infrared, dielectric, and NMR spectroscopy. Infrared spectroscopy is used by various researchers 19,20 to monitor hydroxyl bond stretching, which is indicative of the state of hydrogen bonding in the network. These works suggest that extensive hydrogen bonding exists in the typical epoxy network, persisting above the T g and up to the point of thermal decomposition.…”

Polyepoxide–water interactions: Influence of the chemical structure of the network

“…The intensity of the b relaxation has been shown to increase as a function of water uptake for DGEBA/diethylene triamine polyepoxide as a consequence of hydrogen bonding between water molecules and hydroxyl groups involved in the relaxation [6,8]. In fact, hydroxyl groups in epoxidee amine networks have been shown to be involved in different types of hydrogen bonding interactions [34], and notably (i) OH polymer /N intra-segmental bonds and (ii) intramolecular dimeric associations between 2 hydroxyl groups linked to the same nitrogen atom, OH polymer /OH polymer . Such interactions have been confirmed by molecular dynamics simulations, and are indeed affected in the presence of water [7]: hydrogen bonding between the water oxygen and hydrogen of the hydroxyl groups is responsible for the reduction of mobility observed.…”

Lifetime assessment of epoxies by the kinetics of thermal degradation

“…Although the mechanisms of thermal,6, 7 oxidative,8 and photooxidative degradation9, 10 and their products are well known, studies on the kinetics are rarely reported. Kinetic data were only reported from thermogravimetric studies of diglycidyl‐bisphenol A/4,4′‐diaminodiphenylsulfone,11 and the generation of acrolein during thermal decomposition 12…”