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

can have a number of diverse properties [56] (resilience, flexibility, rigidity) depending on the choice of combined substances. A polyurethane is any polymer consisting of a chain of organic units joined by urethane (carbamate) links. Polyurethane foams are formed through step -growth polymerization by reading a monomer containing at least two isocyanate functional groups with another monomer containing at least two hydroxyl (alcohol) groups in the presence of a catalyst [56-60].
2.7.3    Chemistry of Flexible Polyurethane Foam
The flexible polyurethane foam chemistry features in two main reactions – the ‘gelation’ (polymerization) and the ‘blow’ reactions. The delicate balance between the two reactions is required in order to achieve foam with a stable open – celled structure and good physical properties. The commercial success of polyurethane foams can be partially attributed to catalysts which help t o precisely control these two reaction schemes. An imbalance between the two reactions can lead to foam collapse, serious imperfections, and cells that open prematurely or not at all.
2.7.4    Gelation ( Polymerization ) Reaction
The gelation reaction or polymeriza tion reaction involves the reaction of an isocyanate group with an alcohol group to give a urethane linkage, thus; 

The heat of this reaction is reported to be approximately 24 kcal per mole of urethane formed [57]. The polyurethane foams usually utilize polyfunctional reactants (isocyanates and polyols), and that leads to the formation of cross linked polymer.
Polyurethane are produced by the polyaddition reaction of a polyisocyanate with a polyalcohol (polyols) in the presence of a catalyst and other additives. The polyisocyanate is a molecule with two or more isocyanate functional groups. R1(N=C=O)n≥2 and a polyol is a molecule with two or more hydroxyl (functional group R 2 – (OH)n ≥ 2.

The reaction of a urethane group with an isocyanate group to form an allophanate group is another possible way to further cross link the polymer.