Facts on Flammability

Slide 23 of 37

Filling materials behave in one of two ways when exposed to flame or heat… they either melt or form a char layer. Char layers differ in the degree to which they are continuous and how well they standup to further exposure to flame. In some tests the char or melt behavior will affect the results of the tests without necessarily reflecting real life performance. And example is the Calif TB 121 mattress test which uses an ignition source of newspapers positioned under the mattress. Fillings and fabrics which char may “pass” because the heat of the ignition source was contained under the mattress, while melting materials, without igniting, formed a hole which allowed the heat of the burning paper to exceed the maximum allowed ceiling temperature. On the other hand, tests which used a fixed location for an ignition point may favor materials that melt away without igniting, while charred materials remain exposed.

FPF can be formulated to resist more severe ignition scenarios. One way is to add hydrated alumina together with the combustion modifying additives to form a char layer with good physical integrity. Evolution of water from the hydrated alumina also reduces heat available to support continued combustion. Another approach is the combination of combustion modifiers and large amounts of melamine. The melt characteristics of this type of formulation may create a product that is very difficult to ignite.

Fabrics are classified by char and melt behavior. Cellulosics tend to char while synthetics tend to melt. Melting fabrics leave the filling materials open to ignition. If the fabric is retreating and the substrate is not ignited by the ignition source, the composite would exhibit satisfactory performance. Small differences in the intensity and duration of the ignition source will show big differences in the performance of composites with nylon or polyester fabrics of equal weight.