| Epoxy resin(EP)possess the advantages including good adhesion,stable chemical properties and it has been widely used in electronic packaging,printed circuit boards and other fields.However,EP thermosets are flammable and it releases lots of dense smoke during combustion,which restrict the application of EP.With the development of miniaturization,ultra-thin and integration of electronic and electrical devices,EP is required to have high flame retardancy,low release of smoke and toxicity.The piperazine pyrophosphate(PPAP)with high phosphorus content and excellent carbonization performance was used to prepare flame retardant EP thermosets.In order to further improve the flame retardant efficiency and smoke suppression performance of EP/PPAP composites,the inorganic fillers such as silica,metal oxides and so on are worked as synergists.However,there are problems such as poor compatibility and dispersion in polymer matrix.In this thesis,the metal-organic frameworks(MOF)containing different transition metal ions were prepared.They possessed large specific surface area,good compatibility with polymer and used as synergists.The resultant MOF combined with PPAP for preparation of EP thermosets with low smoke release and high flame retardant efficiency.The related contents as following:In this thesis,the nickel ions containing metal-organic framework materials(Ni-MOF)was firstly prepared and acted as the synergistic agent for EP/PPAP composites.When the mass ratio of PPAP and Ni-MOF was 99:1 and the total loading amount of flame retardant additives was 5 wt%,the thermosets achieved UL-94 V-0 rating during vertical burning tests,and the limiting oxygen index(LOI)value was 29.3%.When 5 wt% PPAP was added,the thermosets only passed UL-94 V-1 rating with the LOI value of 26.7%.Besides,the addition of a small amount of Ni-MOF improved the self-extinguishing performance of EP thermosets.Compared with EP/PPAP thermosets,the peak heat release rate(PHRR)of EP/PPAP/Ni-MOF thermosets decreased by 25.44%,the total heat release(THR)reduced by 11.11%,the total smoke release(TSP)declined by 3.12%,and the residual char at the end of combustion increased from12.57% for EP/PPAP to 22.27% under the same loading amount of flame retardant additives.The nickel ions in Ni-MOF rapidly complexed and crosslinked with the phosphoric and polyphosphoric acid generated from the thermal degradation of PPAP.As a result,more phosphorus elements remained in condensed phase during combustion.Meanwhile,the sufficient char layer with good strength was generated,which effectively inhibited the release of smoke and combustible gas during combustion of EP,and the flame retardant performance was enhanced.According to the excellent smoke suppression properties of cobalt ions,the cobalt ions containing metal-organic framework(Co-MOF)was prepared and then combined with PPAP for the modification of EP.When the mass ratio of PPAP and Co-MOF was 95:5 and the total loading amount was 4 wt%,the EP thermosets achieved UL-94 V-0 rating with the LOI value of 30.1%.It demonstrated that Co-MOF and PPAP exhibited synergistic effect for flame retardant EP thermosets.Compared with EP/PPAP thermosets,the THR decreased by 6.99%,and the TSP declined by 5.54%.Cobalt ion crosslinked with the decomposition products of PPAP and catalyzed the charring of EP thermosets.The generated char layer was reinforced and achieved good synergistic flame retardant performance.Multiple metallic ions can exert synergistic catalytic effects.In this thesis,the MOF materials containing nickel and cobalt ions(Co&Ni-MOF)was prepared and introduced into EP/PPAP composites.When the mass ratio of PPAP and Co&Ni-MOF was 97:3 and the total loading amount was 4 wt%,the EP thermosets passed UL-94 V-0 rating with the LOI value of30.2%.Compared with that of EP/PPAP thermosets,the PHRR,THR and TSP value of EP/PPAP/Co&Ni-MOF thermosets decreased by 11.93%,15.90%,9.44%,respectively.Compared with the above two mono-metal-containing MOF materials,Co&Ni-MOF presented better smoke and fire suppression performance.It demonstrated that the MOF materials containing bimetals exerted synergistic catalytic and flame retardant effects for EP/PPAP composites.Consequently,the flame retardant efficiency and fire safety performance of EP thermosets were further improved. |
