A method for producing a modified form of an aromatic amine compound represented by the following structure I: where A is an amine group —NHR, R is independently selected from hydrogen, linear and branched alkyl groups having 1 to 6 carbon atoms, preferably A is NH2; X is a halogen selected from Cl, Br, F, I, and At, or hydrogen (H). The method includes heating the aromatic amine compound, in its initial crystalline form, to a temperature above its melting point in order to obtain a molten material, then cooling the molten material to a temperature below the melting point of the crystalline compound so as to produce an amorphous, glassy form of the aromatic amine compound. The modified aromatic amine compound is suitable as a curing agent in resin compositions that are used for fabricating fiber-reinforced composites.