This study investigates the effects of the incorporation of nanoparticles on the reaction to fire of an epoxy resin containing a conventional intumescent flame retardant. Two types of nanoparticles are considered: OctaMethylOligomericSilsesquioxanes (OMPOSS) and Carbon NanoTubes (CNTs). The combination of an intumescent phosphorus-based flame-retardant (APP) and CNTs provides no enhancement of the reaction to fire of this system. In contrast, using OMPOSS in combination with APP provides a large synergistic effect via an intumescence phenomenon. The study of the thermal degradation of these systems shows that the interactions between these fillers modify the viscosity of the degraded matrix. The trapping of degradation gases is enhanced in the case of APP/OMPOSS, which results in the creation of an intumescent protective layer earlier than with the reference system containing APP alone. Furthermore, the presence of OMPOSS permits the creation of silicophosphates which reinforce the residue. In contrast, the residue of the formulation containing carbon nanotubes is excessively stiff and it cracks during combustion, hindering the proper formation of the protective layer.

Phosphorus‐based products are able to strongly reduce the flammability of epoxy resins. In order to further improve their fire behavior, combinations of a conventional flame retardant (ammonium polyphosphate [APP]) and two other particles have been investigated. The partial substitution of APP by carbon nanotubes reveals an antagonism between these two compounds in terms of heat release rate measured by mass‐loss calorimetry. On the contrary, the combination with octamethyl polyhedral oligomeric silsesquioxane leads to a huge synergistic effect. These effects are mainly attributed to the char structures. Furthermore, the two systems were studied by thermogravimetric analysis, and they exhibit modifications of the degradation temperatures. The existence of different stabilization effects was also revealed. Copyright © 2011 John Wiley & Sons, Ltd.