Melamine hydrobromide

Hydrobromide. A complex process takes place in the first step of weight loss of melamine hydrobromide (250-400 C) as shown by the DTG curve of Figure 6. The products evolved in this step were shown to be a mixture of melamine hydrobromide (IR) and ammonium bromide (IR and X-ray). The IR spectrum of the residue (55% at 400 0 which is compared with the original salt in Figure 7, is identical with that of reference melam hydrobromide. Furthermore, the IR of the residue... 

Figure 6. TG, DTG curves and rate of ammonia evolution (arbitrary units) for melamine hydrobromide. Conditions as Figure 2.

Melam hydrobromide undergoes thermal degradation between 450-550 0 (2nd step, Figure 6) with complete elimination of bromine either through evolution of ammonium bromide, which is the major product, or melamine hydrobromide as shown by IR. Also a small amount of free ammonia is evolved in this step in which melon is formed as shown by the IR of the residue at 550 0 (ca. 35% of original melamine hydrobromide). 

Similarly to melamine hydrobromide, in the second step of weight loss (370-450 0, Figure 8), IR data show that melam nitrate evolves further ammonium nit rate,ammonia and melamine nitrate giving melon which decomposes completely to volatile products above 500 C. The degradation scheme is then ... 

Figure 7. IR of melamine hydrobromide (A) and of residue at 400 C (B) melam hydrobromide (by comparison with reference compound).

Nitrogen-containing FRs (without any phosphorus compounds) hold only a small share of the global FR market at present, although their popularity is growing. The main active ingredients are usually melamine cyanurate and melamine hydrobromide, although melamine phosphate is used in intumescent FR systems in combination with pentaerythritol. Melamine based flame retardants employ several modes of flame retardant action. 

Italy s Domus Chemicals produces intumescent compounds containing nitrogen and phosphorus based chemicals for polyolefins and TPEs. Domus also sells melamine hydrobromide as a flame retardant for PP. 

Ammonia is evolved here in the condensation process of melamine to melam whereas the respective ammonium salts are evolved in the case of the hydrobromide and nitrate. Reactions 9 and 9b show that ammonia should be neutralised by pyrosulphuric acid groups. In TG we have found that diammonium pyrosulphate eliminates ammonia above 350 C, with however complete decomposition ... 

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