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

4.3    Flame Propagation Rate

The effects of the flame retardants on flame propagation rate of the polyurethane foam are shown in Table 8, fig. 5, from the results, it is obvious that the flame propagation rate reduced with the increase in concentration of the two flame retardants. However, tri ammonium orthophosphate showed a higher impact of reduction of the propagation rate more than melamine. Flame propagation rate is simply the velocity of the flame along the vertical length of the material, so a reduction of such is favourable in fire chemistry of materials.
Moreso, it is not surprising that tri ammonium orthophosphate reduced the propagation rate more than the melamine, bearing in mind the mechanisms (condensed and vaporized phase), fire retardancy associated with phosphate and nitrogen based compounds [45,50]. The observed drastic reduction of flame propagation rate is expla ined thus; at high temperature t ri ammonium orthophosphate decomposes according to the equation.

At    high    temperature,            tri ammonium        orthophosphate decomposes into oxy    – phosphoric acid plus NH 3. The phosphoric acid catalys es charring in polymer, and the char prevents further combustion of the material as already explained. The production of difficulty incombustible char that acts as insulation, and prevents further combustion of the        polymer        material        (i.e.    further    flame        spread    or propagation        is            common        with        phosphorus    based        flame retardants). This explains why the samples retarded with triammonium            orthophosphate        have        reduced    flame propagation rate in concentrations more than those retarded with melamine. Therefore, tri ammonium orthophosphate may be preferred for reduction of the ignition time of flexible polyurethane foams in place of melamine.