Fire and mechanical properties of DGEBA-based epoxy resin cured with a cycloaliphatic hardener: Combined action of silica, melamine and DOPO-derivative

The effect of the addition of additives such as melamine (Mel), silica nanoparticles and a phosphorus-based compound, i.e. 3-(6-oxidodibenzo[c,e][1,2]oxaphosphinin-6-yl)propenamide (DA), on the fire and mechanical performance of a bisphenol A diglycidyl ether (DGEBA)-based epoxy resin cured with isophoronediamine has been investigated. A UL 94-V0 classification was achieved for epoxy resin containing DA at 2 wt% of phosphorus loading. However, addition of silica nano particles was necessary to avoid melt dripping. The incorporation of DA and Mel to the epoxy resin promoted a remarkable reduction (48% to 70%) in the heat release rate (HRR) values, a significant delay (up to 47%) in the ignition time in cone calorimetry experiments, and thus an increase (~75%) in the time to flashover. Evolved gas, thermal and fire analysis was used to propose the combined mode of action of DA, Mel and silica in the fire performance improvement of the epoxy system. Tensile and three-point bending flexural tests showed that the addition of DA increases the rigidity of the resin, resulting in a strong increase in the Young's modulus (up to 34%) and in a slight reduction in fracture strength, elongation break and toughness which is typical for non-reactive additives.