Effect of APP microcapsules on flame retardant and mechanical properties of epoxy resins

Flame retardant and mechanical properties of epoxy resin (EP) composites were studied containing ammonium polyphosphate (APP) and APP microcapsules with a shell of epoxy resin (EPAPP) and melamine-formaldehyde resin (MFAPP). The results indicate that APP exerts its good flame retardancy in EP at 7% loading, with the limiting oxygen index (LOI) of 28.8% and a UL 94 rating of V-0. The microencapsulation of APP with about 10% EP and MF resin does not decrease the flame retardant properties of APP microcapsules in EP. It is found that the mechanical properties of the EP composites containing EPAPP or MFAPP are greatly improved compared with APP, especially the impact strengths of the EP composites with EPAPP and MFAPP, 100% and 150% higher than that of the EP composite containing APP, respectively. Moreover, the addition of APP and APP microcapsules into the EP resin does not affect the insulation of the composites.