Study On High Temperature Resistant,Flame Retardant And Low Toxic Resin System

VE is easy to burn,which greatly limits it application in rail transportation,shipping and other special fields.Halogenated compounds have been widely used to develop vinyl epoxy resins with excellent flame retardancy.Therefore,it is urgent to develop a high efficiency non-halogenated flame retardant vinyl epoxy resin.In this paper,two kinds of flame retardants were synthesized:DOPO-POSS and KH550-DOPO-POSS,a series of modified vinyl epoxy resins were prepared by blending/copolymerization of different contents of flame retardants and tetrobutyl titanate(TBT)with MFE-711 vinyl epoxy resin,and a multi-component synergistic flame retardant system was successfully constructed.The main contents are as follows:The cage and ladder structured phosphorus-containing polyhedral oligomeric silsesquioxanes(DOPO-POSS)have been synthesized through the hydrolytic condensation of 9,10-dihydro-9-oxa-10-phosphenanthrene-10-oxide(DOPO)and triethoxyvinylsilane(VTES).Its chemical structure was characterized by fourier transform infrared spectroscopy(FTIR),¹H and ²⁹Si nuclear magnetic resonance(NMR)spectroscopy,X-ray diffraction(XRD)and matrix-assisted laser desorption ionization time of flight(MALDI-TOF)mass spectrometry.DOPO-POSS exhibited good solubility in vinyl epoxy resin(VE),and it was used with tetrabutyl titanate(TBT)to construct a phosphorus-silicon-titanium synergy system.Mechanical properties,thermal stabilities and flame retardancy of the resultant VE composites were investigated by three-point bending tests,thermal gravimetric analysis(TGA),dynamic mechanical analysis(DMA),limiting oxygen index(LOI),UL-94 vertical burning test and cone calorimetry.The experimental results showed that with the addition of only 4 wt%DOPO-POSS and 0.5 wt%TBT showed good mechanical properties and thermal stabilities comparable to pure VE,the limiting oxygen index value(LOI)increased from 19.5 of pure VE to 24.2.The peak heat release rate(PHRR),total heat release(THR),smoke production rate(SPR)and total smoke production(TSP)decreased by 57.1%,26.9%,18.1%and 13.7%,respectively.The char residue and pyrolysis volatiles of VE composites was investigated by FTIR,SEM,EDX,XPS,TG-IR,Py-GC/MS.The results showed that the radical quenching effect of phosphorus in the gas phase;the stable Si O₂ ceramic phase formed by Si and the synergistic effect between phosphorus and Ti accelerated the formation of residue char,which had the characteristic of honeycomb cavity in the interior layers and compact exterior layers,preventing the heat flow and transfer to improve the flame retardancy of the composites.The half-cage and cage structures phosphorus and nitrogen-containing polyhedral oligomeric silsesquioxanes(KH550-DOPO-POSS)have been synthesized through the Kabachnik-Fields reactions of 9,10-dihydro-9-oxa10-phosphaphenanthrene-10-oxide(DOPO),paraformaldehyde(POM)and 3-aminopropyltriethoxysilane(KH550).Its chemical structure was characterized by fourier transform infrared spectroscopy(FTIR),¹H and ²⁹Si nuclear magnetic resonance(NMR)spectroscopy,X-ray diffraction(XRD)and matrix-assisted laser desorption ionization time of flight(MALDI-TOF)mass spectrometry.KH550-DOPO-POSS exhibited good solubility in vinyl epoxy resin(VE),and it was used with tetrabutyl titanate(TBT)to construct a phosphorus-nitrogen-silicon-titanium synergy system.Mechanical properties,thermal stabilities and flame retardancy of the resultant VE composites were investigated by three-point bending tests,thermal gravimetric analysis(TGA),dynamic mechanical analysis(DMA),limiting oxygen index(LOI),UL-94 vertical burning test and cone calorimetry.The experimental results showed that with the addition of only 4 wt%KH550-DOPO-POSS and 0.2 wt%TBT showed good mechanical properties and thermal stabilities comparable to pure VE,the limiting oxygen index value(LOI)increased from 19.5 of pure VE to 29.2 and passed UL-94 V-1 rating.The peak heat release rate(PHRR),total heat release(THR),smoke production rate(SPR)and total smoke production(TSP)decreased by 42.4%,18.1%,10.6%and 10.8%,respectively.The char residue and pyrolysis volatiles of VE composites was investigated by FTIR,SEM,EDX,XPS,TG-IR,Py-GC/MS.The results showed that the radical quenching effect of phosphorus and nitrogen nonflammable gas in the gas phase;the stable Si O₂ ceramic phase formed by Si and the synergistic effect between phosphorus and Ti accelerated the formation of residue char,which had the characteristic of honeycomb cavity in the interior layers and compact exterior layers,preventing the heat flow and transfer to improve the flame retardancy of the composites.