Synergistic flame retardancy and smoke suppression of white mud filler in intumescent flame retardant epoxy resins
To obtain the resource utilization of ammonia-soda white mud,the white mud fillers were prepared through drying,crushing,and chemical surface modification processes.The white mud fillers were applied as a synergist to prepare intumescent flame retardant epoxy resins with typical intumescent flame retardant system of ammonium polyphosphate-pentaerythritol-melamine.The effects of white mud fillers on flame retardancy property,smoke suppression property,and char-forming ability of intumescent flame retardant epoxy resins were systematically studied through tests of the Limited Oxygen Index(LOI),the cone calorimeter and the thermo-gravimetric analyzer,etc.The results of experiments prove that the addition of white mud fillers can significantly reduce the heat release and smoke production of intumescent flame retardant epoxy resins,showing excellent synergistic flame retardant and smoke suppression effects.Especially,the presence of 5％KH550 Modified-White Mud Filler(KWM)in intumescent flame retardant epoxy resin increases the LOI value from 29.1％to 30.5％,reduces the smoke density rating from 58.32％to 29.33％,decreases peak heat release rate from 328.7 kW/m2 to 234.6 kW/m2,and reduces the peak smoke production rate from 0.071 m2/s to 0.048 m2/s.In addition,the thermogravimetric analysis and char layer analysis demonstrate that the white mud fillers exhibit excellent synergistic char formation effects in intumescent flame retardant epoxy resins.The addition of 5％KWM in intumescent flame retardant epoxy resin generates more aromatic structures and phosphorus-containing cross-linked structures in the condensed phase compare with intumescent flame retardant epoxy resin without white mud filler.The structures enhance the denseness and thermal insulation of the char layer,which effectively segregates heat,combustible compounds,and smoke particles.Besides,the intumescent flame retardant epoxy resin containing 5％KWM reaching 24.5％of char residues at 700 ℃ exerts superior char forming ability than those containing other types of white mud fillers.
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