Intumescent fire-retardant systems

The use as fire retardants of intumescent systems which on heating give a swollen char is reviewed. Early developments in intumescent organic coatings are described, which provided fundamental knowledge on the chemical composition of intumescent systems. The more recent introduction of intumescent additives into polymeric materials is discussed, with reference to specific problems derived from dilution in the polymeric matrix. The results obtained so far in studies of chemical processes which occur on heating typical intumescent systems, such as mixtures of ammonium polyphosphate with pentaerythritol, are presented.