Melam/melem/melon

Melamine and its salts are widely used in formulations of fire retardant additives, particularly of the intumescent type (4-71. The role played by melamine structures in these additives is however not yet understood. The thermal behaviour is of paramount importance in studies of the fire retardance mechanism. It is known that melamine undergoes progressive condensation on heating with elimination of ammonia and formation of polymeric products named "melam", "melem", "melon" (8.91. The following schematic reaction is reported in the literature (10-121 ... 

Melamine [108-78-1]. This inexpensive solid melts with vaporization at about 350°C and, if evaporation is constrained, decomposition also occurs to ammonia and nonvolatile condensation products— melam, melem, and eventually melone. It is occasionally used by itself as a flame retardant but more often used as a blowing agent and flame-retardant adjuvant in intumescent coatings, elastomers, and plastic formulations (138) as well as in flexible polyurethane foams (139,140). 

Upon heating, to whatever extent it does not sublime away, melamine can undergo progressive condensation with evolution of ammonia and formation of thermally stable condensates, known as melam, melem, and melon. This reaction competes with melamine volatilization and is more pronounced if the volatilization of melamine is impeded for example, by trapping in the charred polymer. 

The by-product ammonium bromide is shown to volatilise in similar conditions in TG. This is a different behaviour altogether from that of melamine in whose thermal condensation melam can be isolated with difficulty only in carefully controlled experimental conditions (11.17). Indeed melem is the condensation product most easily isolated and this led some authors to doubt that melam could be an intermediate product of the condensation of melamine to melem and melon (19.22). 

---