THERMAL-BEHAVIOR OF GUANIDINIUM DIHYDROGE NPHOSPHATE AND DIGUANIDINIUM HYDROGENPHOSPHATE

The thermal decompositions of four kinds of guanidinium salts, such as guanidinium dihydrogenphosphate(1), diguanidinium hydrogenphosphate(2 ), diguanidinium carbonate(3), and guanidinium nitrate(4), were invest igated. The thermal behaviors of these samples under a nitrogen atmosp here differ from one another. In GC/MS measurements of volatile produc ts generated by the thermal decomposition for these samples, major fra gment ions were confirmed as water, ammonia, isocyanic acid, and carbo n dioxide. Further, from the mass spectrometry and IR analysis of vola tile products for four kinds of samples, the formation of identical gu anidine derivative during thermal decomposition process was confirmed in all cases. In IR analyses for residues of 1 and 2 heated to various temperatures, their spectra differed from each other until temperatur e raised at 300 degrees C. Above 300 degrees C, the infrared band of g uanidinium ion completely disappeared and then the thermal products of both samples showed identical spectra. Above 500 degrees C, polymetap hosphates and diphosphorus pentaoxides were formed by the thermal deco mposition and subsequently occurred condensation reactions. The kineti cs were partially resolved and activation energies were estimated for the thermal decomposition of guanidinium phosphates. The highest value of activation energies for 1 and 2 were observed at weight loss of ab out 20%. We suggest that guanidinium phosphates decomposed through the formation of guanidine and urea derivatives, such as biguanide and am idinourea.