Synergistic and antagonistic effects in flame retardancy of an intumescent epoxy resin

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.