Investigation Of Effects Of Two Flame Retardants On The Fire Characterisit Ics Of Flexible Poly Ether Foam

condensation of the melamine fraction which does not sublimate.
Melamine also shows considerable contribution to the formation of a char layer in intumescent process. The char layer acts as a barrier between oxygen an d polymeric decomposition gases. Char stability is enhan ced by multi- ring structures such as melem and melon, formed during self condensation of melamine.
Melamine also acts as a b lowing agent for the char, enhancing the heat barrier functionality of the char layer.
When melamine is exposed to heat and flames , it decomposes, absorbing heat and creating a cooling effect. The time to ignition is delayed significantly as nitrogen, liberated by melamine during its decomposition, dilutes the oxygen which in turn, inhibits the spread of flames and the generation of smoke.
Moreover, when melamine based flame -retardant (intumescent) coatings are exposed to fire they degrade. As melamine also acts as a blowing agent a stable insulating charred foam layer is formed. As a result the substrate material beneath the charred foam layer is protected from damaging heat.
2.5.3    Applications and benefits of Melamine
Melamine is used to make kitchen cupboards surfaces and utensils. Melamine is processed with formaldehyde into resins used in the produc tion of wood – based panels, laminates for kitchen cabinets, floors, table tops, coatings for the automobile industry . Melamine is also processed into moulding compounds from dinner ware and electrical appliances [43].
Melamine is used as a flame retardant with the advantages of being low cost, halogen free and offering excellent ignition resistance. Melamine retards flame propagation and has good performance with regard to corrosion, smoke formation and the relatively low toxicity of the combustion gases.
A number of melamine condensates, also containing only nitrogen, carbon and hydrogen, are also used as flame retardants, because they offer higher th ermal stability during processing of the polymers to which they are added.
These condensates include Melem and Melon which are derivatives    of    tri-s-triazine    (1,3,4,6,7,9, b)    – heptaazaphenalene or        cyamelurine a conden sate of two melamine molecules [ 44].
2.5.4    Application s of melamine and its derivatives Melamine and its derivatives are widely used to improve fire safety of flexible polyurethane foams, polyamides (nylons) and thermoplastic polyurethanes. They are also used as a constituent of int umescent coating fire protection system. They act by combination of effects; in contact with heat they decompose, acting as a heat sink, and release inert nitrogen gases which dilute the oxygen and flammable gases. They also    chemically    and    physically    inhibit    burnin g    (char formation) and contribute to intumescent coating formation (blows char into protective foam which prevent dropping)
2.5.5    Benefits of Melamine [44]
Melamine is particularly effective in nitrogen containing polymers    (polyurethanes,    polyamides),    b ecause    of    the synergy with the nitrogen content of the melamine flame retardant.
It has low water solubility (durability). It offers high levels of UV absorption, thus helping to protect plastics from damage by sunlight. It is environmental friendly because it contains nitrogen, carbon and hydrogen based molecules. Melamine has effective improvement of fire safety through multiple effects.
It offers low toxicity, safety, widely recognized product. Melamine derivatives allow use in an increasing range of polymers and application including high temperature polymer processing.
2.6    Tri ammonium orthophosphate as flame retardants [45-50]
There are many kinds of ammonium ortho - and condensed phosphates (Ammonium phosphate tribasic or tribasic ammonium phosphat e, trihydrate). The phosphates are used as flame retardants, chemical fertilizers, food additives, and dye-leveling agents. The phosphorus – nitrogen compounds are effective flame retardants for plastics like polyurethanes, polyamides and telephthalates (P ET). Triammonium orthophosphate is an inorganic salt of phosphoric acid and Ammonia. It is a white alkaline solid that is soluble in water. The structure of tri ammonium orthophosphate is thus: