Flame Retardancy Of Epoxy Resin/Nitrogen And Phosphorus-Containing Ultrathin Compounds Composites

Epoxy resin?EP?has excellent physical and mechanical properties,electrical insulation properties,bonding properties and good process flexibility.It is widely used in mechanical,electrical,communication and vehicle manufacturing industries.But the flammability of EP limits its application.In this paper,the polymer/compound composites flame retardant system and polymer/transition metal compound composites material flame retardant system are reviewed based on the research status at home and abroad and the research work of our research group.I think the advantages of ultra-thin lamellar structure of ultra-thin compound containing nitrogen and phosphorus,flame retardant effect of nitrogen and phosphorus and carbonization effect of transition metal are combined.This is expected to become a new flame retardant for flame retardant polymer materials.Based on this,ultrathin compounds nitrogen-doped cobalt phosphate?Co-PMP?,iron hydroxy phosphate?FHP?,cobalt nickel phosphate?NiCoPO₃?and cobalt nickel organometallic framework?CoNi-MOFs?containing N and P elements were designed and synthesized in this paper,and modified or synergistically by different methods.The effects of the above systems on the thermal stability,flame retardancy and fire safety of epoxy were studied.The flame-retardant mechanism was also explored.In this paper,N and P-containing precursor methylene phosphonic acid?PMP?was synthesized by condensation reflux method.Then N and P-containing ultrathin compound nitrogen-doped cobalt phosphate?Co-PMP?was synthesized by hydrothermal method.It is used for flame retardant EP.The results show that Co-PMP can promote carbon formation and improve the thermal stability of composites.The composites UL-94 passed the V-1 test,the LOI value was also improved.More than,the addition of Co-PMP can reduce the THR and PHRR values of the composites to a certain extent,which also indicates that the flame retardancy is improved.In order to further improve the flame retardancy of EP,ultrathin compound iron hydroxy phosphate?FHP?containing P was synthesized by hydrothermal method and modified by hexachlorocyclotriphosphazene?HCCP?to obtain HCCP-FHP.It's added to EP,then the flame retardancy effect was tested.The test results show that the thermal stability of the composites is improved,and the amount of carbon residue is significantly increased,improve 14.8 wt%.The LOI value of the composites can be obviously improved,and the addition amount of 2 wt%can reach the V-1 level of UL-94,and the flame retardancy is improved;The THR and PHRR values of composites can be significantly reduced by adding 6 wt%HCCP-FHP.The improvement of the thermal stability and flame retardancy of EP/HCCP-FHP is mainly attributed to the high thermal stability and excellent catalytic carbonization of HCCP-FHP itself.In order to further improve the flame retardancy of composites and simplify the production process,ultrathin compound cobalt nickel phosphate?NiCoPO₃?containing P was synthesized by hydrothermal method,and modified with triphenylphosphine oxide?TPPO?to obtain TPPO-NiCoPO₃,which was added to EP for flame retardant EP.The results show that TPPO-NiCoPO₃ can improve the carbon residue of the composites,improve 12.2wt%.The stability at high temperature is improved.The flame retardancy effect can best pass the V-1 level tested by UL-94,the LOI value can be increased to 31.3%.The flame retardant is greatly improved.The THR and PHRR values of composites can be significantly reduced by the addition of TPPO-NiCoPO₃.The main performance is the condensed phase flame retardant mechanism,which effectively improves the flame retardancy,thus improving the fire safety.In order to further improve the flame retardancy of composites,simplify the production process and application range,ultra-thin compound cobalt-nickel metal organic framework?CoNi-MOFs?containing N element and transition metals Co and Ni element was synthesized by hydrothermal method.CoNi-MOFs has a typical ultra-thin lamellar structure,and is added to EP in a certain proportion with DOPO for flame retardant EP.The results show that the LOI value of EP/?1 CoNi-MOFs/3 DOPO?composites increased to 33.3%,UL-94 passed the V-0 test,and the combustion time was only 6.4 s;Compared with pure EP,EP/?1 CoNi-MOFs/3 DOPO?PHRR is reduced by 36.7%,THR is also significantly reduced,and flame retardancy is significantly improved.Due to the good compatibility between DOPO and EP,the system solves the problems of large addition amount and low flame retardancy grade.The flame retardancy is obviously improved when the addition amount is only 1 wt%?CoNi-MOFs?,which can improve the flame retardancy while maintaining the excellent performance of EP.Thus,it can improve application range and fire safety.