Epoxy composites of reduced flammability

The effect of the so called environment friendly hybrid flammability reducing fillers, i.e. the halogen/antimony-free ones containing phosphorous, nitrogen and silicon on the utility properties of carbon reinforced epoxy laminates was studied. The total content of the fillers did not exceed 23 wt.%. The flame resistance of the laminates aimed as parts of aircraft construction was determined. The fire retardancy mechanism of the hybrid fillers was investigated by SEM/EDS examination of partially burned laminates. The best combination of flammability reducing fillers for the epoxy composite matrices consisted of 15 wt.% ammonium polyphosphate, 5 wt.% dipentaerythritol, and 3 wt.% organofilized bentonite. The synergy of silicon and phosphorus in this composition provided material of UL-94 flammability class V-0.