As one of the five engineering plastics,polyoxymethylene(POM)possesses very good excellent performance.But it is easy to burn due to its special molecular chain structure,the limiting oxygen index is only about 15%,and its melt drops seriously during the combustion process with severe releases of formaldehyde gas and heat at the same time.Thus,flame retardant modification of POM is urgently needed so as to enlarge its application area and enhance its added value.In this paper,three new types of intumescent flame retardant system(IFR)were developed,and the corresponding flame retardant POM composite materials were obtained by melt blending.Their flame-retardant property including UL-94,limit oxygen index and cone calorimeter test,thermal analysis(TG),electronic scanning electron microscopy(SEM)and mechanical properties and the related mechanisms were studied.The main research contents are as follows..1)Novolac/APP/ME flame retardant POM composites were prepared using ammonium polyphosphate(APP),melamine-coated APP(MF-APP),silane-coated APP(GW-APP),epoxy resin coated(MC-APP),and ultrafine APP(UFP-APP)as acid source respectively,compounding novolac resin(Novolac)as carbon source and melamine(ME)as gas source,complex flame retardant POM.The effects of different types of APP on the flame retardancy and the mechanical properties of POM were investigated.The results show that the synergistic effect of Novolac/ME and GW-APP is best among all kinds of APP.When the addition amount of Novolac/GW-APP/ME is 40 wt%,the flame-retardant POM reaches UL-94 V-0 and the limit oxygen index is up to 34.0%.However,the total addition of IFR is still high and has a great adverse effect on the mechanical properties of the composite materials.2)BOZ/APP/ME flame retardant POM were prepared using a novel carbon agent,benzoxazine(BOZ),compounding with gas source ME and acid source selected from APP,GW-APP and MC-APP.The effects of different partition ratio and adding amount on the properties of flame retardant POM were studied.The results indicate that BOZ has excellent synergy with APP and ME,its optimal adding amount is 4.0%by weight.When the amount of BOZ was 4%and the amount of GW-APP added is 15%and 20%,the flame retardant grade reached UL94 V-1 and UL94 V-0 respectively,and the LOI was 39.6%and 49.6%,indicating exceedingly good synergistic flame retardant effect between GW-APP and BOZ.3)Furthermore,graphene oxide(GO)was utilized as synergistic agent compounding with BOZ/APP/ME to modify POM.The effects of GO on the properties of POM composites were discussed.The results show that GO has exceedingly good synergistic flame retardant effect with BOZ/APP/ME intumescent flame retardant system.When the addition amount of GO was 0.1%,the flame retardant BOZ/APP/ME is 30%,the flame-retardant POM achieves UL-94 V-1 level,the limiting oxygen index reached 57.8%which improved significantly.Moreover,GO has good influence on the mechanical properties of the composites,especially the notch impact properties. |