Overview of fire retardant mechanisms

The flammability of polymeric materials depends on thermal degradation processes which occur on exposing them to heat. Fire retardant systems have been developed which reduce polymer flammability by various mechanisms which are not yet fully understood. Innovations to the traditional fire retardant approach are required by recent recognition of hazards which have previously been neglected or underestimated. This challenging task is likely to be satisfactorily accomplished only if more detailed information on mechanistic aspects becomes available. Thermal degradation mechanisms which take place in the polymer matrix are of paramount importance in the understanding of polymer combustion and fire retardance. The parameters which affect the thermal behaviour of polymeric materials, such as oxygen concentration, pressure and heating rate, are examined in relation to combustion conditions. Examples of recent mechanistic studies of intumescent and halogen based fire retardants are reviewed and discussed.