A model compound (I), representative of the structure resulting from the first step of curing in diglycidylamine-aromatic amine systems, was prepared from diglycidylamine and N-ethylaniline. After thermal treatment, the fraction resulting from intramolecular processes, that is to say possessing the same molecular weight as the initial compound (I), was isolated by preparative GPC. This fraction was shown by GPC, HPLC and 13C NMR spectroscopy, to contain morpholine, as well as corresponding 7-membered cyclic ethers which were identified by comparison with the products of a process said to actually give morpholine derivatives. Another non ether-forming cyclisation reaction was also detected, resulting in the formation of a 3-hydroxy-1,2,3,4 tetrahydroquinoline derivative, by attack on an aromatic nucleus by the epoxy directly bonded to it. Apparently, this reaction has not been previously described.