Effect of solvent on residual strain in clear epoxy coatings

Coatings were formed from solutions of solid and liquid epoxy resins, cured with diethylenetriamine. The residual internal strain was measured and found, in all cases, to be considerable. The residual strain in coatings formed from the faster evaporating solvents showed no variation with coating thickness, but exhibited a small dependence on the concentration of the coating solution. These coatings, like lacquers, are considered to solidify whilst still in a thermoplastic state, with subsequent crosslinking. Coatings cast from a very slow-evaporating solvent had a residual strain which increased greatly with coating thickness, because they solidified owing to the formation of a crosslinked network. Liquid epoxy resin formed coatings with much higher residual strain and poorer adhesion when cast from solution than when applied as a solventless formulation.Des rev\ueatements ont \ue9t\ue9 pr\ue9par\ue9s \ue0 partir des solutions de r\ue9sines epoxydes, liquides ou solides, durcies par di\ue9thyl\ue8 netriamine. La tension r\ue9siduelle a \ue9t\ue9 mesur\ue9e et trouv\ue9e consid\ue9rable dans tous les cas. La tension r\ue9siduelle des rev\ueatements contenant des solvants qui \ue9vaporent plus rapidement ne d\ue9montre aucune variation en fonction de l'\ue9 paisseur du rev\ueatement, mais elle se depend l\ue9g\ue8rement de la concentration de la solution de r\ue9sine. On consid\ue9re que ces rev\ueatements se solidifient pendant qu'ils sont encore \ue0 l'\ue9tat thermoplastique, et que la r\ue9ticulation se produit subs\ue9quemment. Les rev\ueatements d\ue9pos\ue9s \ue0 partir d'un solvant \ue0 une tr\ue8s faible vitesse d'\ue9vaporation avaient la tension r\ue9siduelle qui augmentait fortement en fonction de l'\ue9paisseur du rev\ueatement, parce que leur solidification \ue9tait due \ue0 la formation d'une structure r\ue9ticul\ue9e. Les r\ue9sines \ue9poxydes liquides donnaient des rev\ueatements dont la tension r\ue9siduelle est beaucoup plus \ue9lev\ue9e et l'adh\ue9rence plus faible lorsqu'ils sont d\ue9pos\ue9s \ue0 partir de leur solution que dans le cas ou ils sont appliqu\ue9s sous forme d'un produit exempte de solvant.Peer reviewed: YesNRC publication: Ye