Melamine/epichlorohydrin prepolymers: syntheses and characterization

The basic catalysis of melamine with epichlorohydrin gives prepolymers that can be used in the preparation of energetic materials. In this work, sodium hydroxide and triethylamine were used as catalysts and ethyleneglycol as initiator. Different reaction conditions were tested and the characterization of the products was carried out by IR and NMR spectroscopy and MS spectrometry, hydroxyl groups content, vapour pressure osmometry and elemental and thermal analysis. Epichlorohydrin reacts with the amine groups of melamine and forms lateral chains with hydroxyl and epoxide end groups, which can be used for curing purposes. The two catalysts lead to similar products, confirmed both by the structure and number of the lateral chains. The melamine/epichlorohydrin ratio was found important for the structure of the final compounds. Chlorine atoms leave the molecules during reaction due to basic catalysis. In the light of the use of the prepolymers in energetic materials, the presence of the 1,3,5-s-triazine ring and the lateral chains with end groups curable by e.g. isocyanates was accomplished with success. However, the loss of chlorine atoms limits to a certain extent their possible substitution by energetic groups.