The use of clay in an EVA-based intumescent formulation. Comparison with the intumescent formulation using polyamide-6 clay nanocomposite as carbonisation agent

This work deals with the use of clay as a filler in an intumescent EVA-based formulation using a charring polymer (polyamide-6) as a carbonization agent. Using PA-6 clay nanocomposite instead of pure PA-6 had been shown to improve the fire properties of the intumescent blend. In this study, using clay as a "classical" filler enabled the same level of FR performance to be obtained in the first step of the combustion as when directly using exfoliated clay in PA-6. But in the second half of the combustion, the clay destabilizes the system and increases the flammability. Moreover, a kinetic modeling of the degradation of the EVA-based formulations shows that adding clay to the blend enables the same mode of degradation and the same invariant parameters as for the polyamide-6 clay nanocomposite containing intumescent blend. It is assumed that these kinetic data can be correlated with the improvement of the fire performance in the first step of combustion as observed under the cone calorimeter. The increase in the flammability by the K-10 in the second half of the combustion shows the advantages of using nanoclay rather than micronclay in an intumescent system.