4. Intumescence and synergy

4.1 Intumescent systems

Among the wide variety of halogen-free flame retardants, intumescent systems represent a very interesting method of fire protection. This concept, which emerged in the 1970s, was originally used for paint-type coatings, but was soon applied to polymers.

An intumescent formulation is defined as such when, when heated above a critical temperature, it begins to swell and char, giving rise – to the formation of a honeycombed charcoal layer of low thermal conductivity on the surface of the – material. This honeycomb layer protects the material from external heat flow. It also prevents the diffusion of oxygen from the air into the polymer and the transport of combustible gases to the flame. Finally, it reduces or eliminates any dripping caused...