Intumescent fire retardant systems: Effect of fillers on char structure

Scanning electron microscopy and microanalysis by energy dispersive system show that the structure of the foamed char obtained on burning polypropylene fire retarded with an intumescent additive system, can be strongly modified in the presence of typical inorganic fillers. Modifications involving both the physical and chemical characteristics of the char might be related to chemical reactions between fillers and acid phosphorus moieties of the fire retardant. Fillers that modify the structure of the char tend to decrease the efficiency of the fire retardant system.