Synthesis And Fire Retardant Property Of Hyperbranched Macromolecular Triazine Charring Agent

Charring agent is an important component of intumescent flame retardant(IFR).At present,the widely used charring agent is linear macromolecular triazine charring agents.Compared with the linear charring agent,the hyperbranched macromolecular triazine charring agent has the some advantages such as more branch points and simpler synthesis processes,but researches on hyperbranched charring agent,especially the relationship between its structure and performance,are relatively few.Therefore,the hyperbranched charring agent,especially the relationship between its structure and performance,is studied in this paper.The piperazine-based hyperbranched charring agents(charring agent-1),ethylenediamine-based hyperbranched charring agents(charring agent-2),propylene diamine-based hyperbranched charring agents(charring agent-3),butyldiamine-based hyperbranched charring agents(charring agent-4)and hexanediamine-based hyperbranched charring agents(charring agent-5)were synthesized through condensation polymerization of cyanuric chloride respectively with piperazine,ethylenediamine,propylenediamine,butyldiamine and hexanediamine by using the mixture of water and acetone as a solvent,and their thermal stability and charring ability were studied by thermogravimetric analysis(TGA).The results show that their optimum synthesis conditions are as follows: n(cyanuric chloride): n(diamine):n(sodium hydroxide)=1.00:1.53:3.00,v(water):v(acetone)=1.0:0.4,w(cyanuric chloride):w(solvent)=1.0:4.7,the low temperature condensation time at 0?5 ? being 2 h,the medium temperature condensation time at 50±2 ? being 2 h,and the high temperature condensation polymerization time at 90±2 ? being 8 h.Under the above conditions,the yield of each charring agent is more than 94%,with the total chlorine content of 0.25?0.52% and the water solubility of 0.24?0.35 g/100 ml.The structure of diamines has little effect on their synthesis,but an obvious effect on their thermal stability and charring ability of charring agents,the thermal stability of charring agent-1 is the best,but that of charring agent-5 is the worst.The synergistic flame retardancy of the above charring agents and ammonium polyphosphate(APP)in PP was studied by limit oxygen index(LOI)determination,vertical combustion test and conic calorometry test(CCT),and compared with piperazine-based linear charring agents(charring agent-6)and piperazine-based triazine charring agent(charring agent-Su)produced by Zhongshan Sutebao New Materials Co.,Ltd.The results show that the structure of the hyperbranched charring agent has significant influence on the flame retardant property as well as the burning behavior of the PP composites.Charring agent-1 has the best synergistic effect in the flame retardancy and suppression on flame propagation and fire intensity,charring agent-2 do the second,and the other three do relatively worse;moreover,the thermal stability,the above synergistic effect of charring agent-1 and the water resistance of the flame retaradnt PP with it are significantly better than that with charring agent-6;in addition,the synergistic flame retardancy of charring agent-1 is largely equivalent to that of charring agent-Su,the water resistance of the flame retardant PP with the former is significantly better than that with the latter,but the synergistic effect of the former in the suppression on flame propagation and fire intensity is slightly worse than that of the latter.The flame retardant mechanism of the hyperbranched triazine charring agent/APP was proposed through the TGA of the IFR/PP composite,the composition and structure analysis of the CCT residues: APP and the hyperbranched triazine charring agent form firstly metaphosphamide cross-linked polymer under high temperature,and then further break into amorphous char,graphitized char,the compounds of carbon and nitrogen and polymetaphosphoric acid.The triazine charring agent and APP exhibit good inter-promotion in the formation of residues,the polymetaphosphoric acid from the decomposition of APP promotes the cracking of the charring agent,and the char and the compounds of carbon and nitrogen exhibit good thermal stabilization on polymetaphosphoric acid.Polymetaphosphoric acid,the char and the compounds of carbon and nitrogen are intertwined to form the residues,and the molten residues are explanded under the action of inert gas from the decomposition of APP,charring agents and PP to form an intumescent char layer.The layer performs the flame retardant effect by insulating heat and oxygen,preventing the composite from further decomposition and the decomposition products from volatilization,which also results in the suppression on the flame propagation and the reduction of fire intensity.The synergistic effect of the charring agent is related to the content of piperzine structure unit in its molecule,the more the unit content(including latent perperazine-ethylene diamine),the better its thermal stability,the higher the content of graphitized char in the CCT residues,and the more dense the intumescent char layer,consequently,the better the synergistic effect in the flame retardancy and suppression on flame propagation and fire intensity.