General Effects of Fillers on Polymer Flammability

Before discussing the special effects of fillers that are active fire retardants, it is useful to recognise that the addition of any particulate, non-combustible, filler to polymers can considerably affect their thermal stability, resistance to ignition and combustion, and the amount and nature of the combustion gases in terms of smoke, corrosion and toxicity. The main general effects are  

The relative importance of these different effects is likely to vary with the polymer type, and its mode of degradation, and also with the type of flammability test. 

On their own, the above effects are not usually sufficient to pass fire resistance tests and additional features are required. The main effects of this type are  

Phosphorus and phosphates, notably ammonium polyphosphate (APP), are an example of the first effect. Nano-clays also appear to enhance char properties, although the mechanisms are not fully understood at present. 

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