| Epoxy resin(EP)is widely applied in housing,automobiles,printed circuit board,adhesive and insulating device due to their excellent properties,such as low density,outstanding electrical insulation,perfect mechanical rigidity,relatively low cost and good adhesion.However,common epoxy resins are flammable and can not satisfy high flame-resistance requirement of advanced materials.It releases a large amount of heat and toxic smoke during combustion,which threatens the safety of people’s life and property and greatly limits the application of epoxy resin.To date,because of high reactivity and compatibility with EP,9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)and its derivatives have become one of most important flame retardants in this field.However,it was found that there have negative effects on the mechanical properties due to lowers the glass transition temperature and DOPO would be volatilized before combustion.In order to obviously improve the flame retardancy of EP composites,a large amount of DOPO would need to be added.So,in order to solve this problem,this paper designed and synthesized three compounds containing DOPO structure to study their effects on the thermal stability and flame retardancy of EP and explore the flame retardant mechanism.An anion with Schiff base structure was synthesized from salicylaldehyde and p-aminobenzoic acid,then its anionic DOPO were synthesized by addition reaction,and intercalated into layers with anions between layers,and incorporated into EP.The structure was characterized by SEM and TGA.The results indicated that DOPO-Ni(OH)2 disperses well in the polymer,which had superior catalytic charring performance in the condensed phase and improve the thermal stability of EP at high temperature and the composite limiting oxygen index(LOI)is improved,and the flame retardant and smoke suppressing properties are improved.but the addition amount of the flame retardant is too high to affect other properties of EP.DOPO-MMT was synthesized by mixed solvothermal reaction.EP/ DOPO-MMT nanocomposites were prepared by melt intercalation method,which were intercalated and exfoliated-intercalated structures.The results indicated that the incorporation of DOPO-MMT greatly improved the thermal,the residue,flame retardant and smoke suppression properties of EP.With the incorporation of DOPO-MMT,the PHRR value,the THR value,and SPR peak value reduced,respectively.The 6 wt% DOPO-MMT has the best results in all EP/DOPO-MMT nanocomposites.These attractive performances can be attributed to the barrier effect and excellent charing performance of DOPO-MMT.However,the bad smoke suppression properties were unfavorable for survivals in fire.DOPO-POSS was synthesized by KH-550,carbon tetrachloride(CCl4)and DOPO,and used for flame retardant EP.The results indicated that DOPO-POSS has a good catalytic carbon formation effect,and the thermal stability is greatly improved compared with the addition of DOPO alone.When the amount of 6 wt% is added,the vertical burning time can reach 10.6s.Significantly reduced heat release rate(HRR),total heat release(THR),smoke generation rate(SPR),total smoke emission(TSP)values. |
