Hexa-[4-(glycidyloxycarbonyl) phenoxy]cyclotriphosphazene chain extender for preparing high-performance flame retardant polyamide 6 composites

Abstract The effects of phosphazene based epoxy resin hexa-[4-(glycidyloxycarbonyl) phenoxy]cyclotriphosphazene (CTP-EP) as a synergistic agent on fire retardancy, thermal and mechanical properties of polyamide 6/aluminum diethylphosphinate (PA6/AlPi) composites were investigated. AlPi and CTP-EP presented an obviously synergistic flame retardant effect for the PA6 matrix. The PA6/AlPi/CTP-EP composites with a thickness of 1.6 mm successfully passed UL-94 V-0 rating with the limiting oxygen index value of 31.0% when the loading amount of AlPi/CTP-EP (mass fraction of 97/3) was 11 wt%. The incorporated CTP-EP improved the complex viscosity of PA6/AlPi/CTP-EP composites due to the chain extending reaction between the epoxide groups of CTP-EP and the terminal groups of PA6 matrix. The CTP-EP stimulated the formation of more sufficient and compact char layer during combustion. The higher melt viscosity and more compact char layer of PA6 composites further inhibited the volatilization of flammable gases, thus the ignition time of PA6/AlPi/CTP-EP composites was prolonged and the released heat was reduced. The introduction of CTP-EP simultaneously enhanced the flame retardant and mechanical properties of PA6/AlPi/CTP-EP composites compared with that of PA6/AlPi composites.