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Melamine (2,4,6-triamino-1,3,5 triazine, CAS nr. 106-78-1) is a white crystalline powder with a melting point of approximately 354°C and a density of 1.573 grams/cc.

Far below its melting point, already at >200°C, melamine is known to vaporize or sublime (diluting the fuel gases and oxygen near the combustion source).

When sublimating it absorbs an amount of heat of 29 kcal/mole, when decomposing it absorbs an amount of heat of ~470 kcal/mole, thus acting as a heat sink in fire situations.

Additionally melamine exhibits low solubility in water and most other solventsexcellent UV absorption above 250nm and a pH of 8.1 .

Flame retardants function by interference with one of the three components that initiate and/or support combustion: heat,fuel and oxygen. Melamine shows excellent flame retardant properties because of its ability to interfere with the combustion process in all stages and in many different ways.

 In the initial stage melamine can retard ignition by causing a heat sink through endothermic dissociation in case of a melamine salt followed by endothermic sublimation of the melamine itself at roughly 350°C. Another, even larger, heat sink effect is generated by the subsequent decomposition of the melamine vapors.

Melamine can be regarded as a "poor fuel" having a heat of combustion of only 40% of that of hydrocarbons. Furthermore, the nitrogen produced by combustion will act as inert dilluent. Another source of inert dilluent is the ammonia which is released during breakdown of the melamine or self-condensation of the melamine fraction which does not sublimate.

Melamine can also show considerable contribution to the formation of a char layer in the intumescent process. The char layer acts as a barrier between oxygen and polymeric decomposition gases. Char stability is enhanced by multi-ring structures like melem and melon, formed during self-condensation of melamine. In combination with phosphorous synergists melamine can further increase char stability through formation nitrogen-phosphorous substances. Last but not least melamine can act as blowing agent for the char, enhancing the heat barrier functionality of the char layer.