Research On Synthesis And Application Of Organic-metal Flame Retardants Containing Phosphorus And Nitrogen

With the improvement of people’s awareness of environmental protection and safety, the development of new halogen-free flame retardants or improving the flame-retardant efficiency of traditional halogen flame retardants through synergism is becoming a tendency in the future. Having focused on the advantages and disadvantages of flame retardant synergistic between the intumescent flame retardants and inorganic metal oxide(metal hydroxide), metal salts, we designed and synthesized organometallic flame retardants containing phosphorus, nitrogen, silicon fire retardant elements in this paper. In addition, we studied the flame retardancy of epoxy resin and cotton fabrics matrix treated by organometallic flame retardants to investigate the synergistic effect of nickel.In this paper, N-(diphenylphosphino)-1,1-diphenyl-N-(3-(triethoxysilyl)propyl) phosphinamine(PNP), nickel(II) ethanedithiolate complexes [(CH3CH2)3OSi(CH2)3N(PPh2)2]NiCl2(PNP-NC) and nickel(II) ethanedithiolate complexes [(CH3CH2)3OSi(CH2)3N(PPh2)2]-Ni(SCH2CH2S)(PNP-NS) were prepared using diphenyl phosphorus trichloride, γ-aminopropyl triethoxysilane, nickel chloride hexahydrate, 1, 2- ethanedithiol as the main raw material. The structures of PNP, PNP-NC, PNP-NS were characterized by FTIR, 1H NMR, 31 P NMR. The synthetic conditions of PNP and the PNP-NS were optimized by single factor experiments. The thermal decomposition behavior of PNP, PNP-NC, PNP-NS were studied by thermal gravimetric anaiysis(TGA). PNP was suitable to fabricate flame retardant cotton fabrics and epoxy resins due to it showed good thermal stability according to TGA tests. PNPNS exhibited excellent char-forming properties by the catalytic of nickel.Secondly, PNP and PNP-NS were applied on cotton fabrics by the dip-pad-cure process respectively. The finishing process was optimized. Thermal decomposition behavior, flame retardancy, and char combustion performance of cotton fabrics treated by PNP and PNP-NS were compared. On the condition that the finished cotton fabric’s add-on was 22.7 ± 0.1 wt%, we can see that the cotton fabrics treated by PNP-NS showed a better performance on the process of combustion and flame retardency than the one treated by PNP from the data of LOI testing and MCC testing. Moreover, the ignition temperature of cotton fabrics treated by PNPNS was lower than the one treated by PNP, which corresponded to the temperature changes at the maximum weight loss rate from the TG test results. These revealed that the cotton fabrics treated by PNP-NS possessed more excellent performance on flame retardant than the one treated by PNP. SEM analyses of char residue revealed that the residue of cotton fabrics treated by PNP contained more intumescent bubble than that treated by PNP-NS, which indicated that the residue of the latter was more compact. The Raman test revealed that the cotton fabrics treated by PNP-NS had a smaller size of carbonaceous microstructures than that treated by PNP.Thirdly, epoxy resin was modified by the PNP or PNP-NS, in which the thermal decomposition behavior, flame retardant properties, combustion performance and the char residue of the flame retardant of the modified epoxy resin were conducted a comparative study. The initial decomposition temperature of epoxy resin modified by PNP-NS was lower than the one modified by PNP when 5 wt% of PNP or PNP-NS was added. The maximum rate of decomposition and the corresponding temperature of the epoxy resin modified by PNP-NS was lower than those modified by PNP when 5 wt% of PNP or PNP-NS was added. The pHRR and THR of the epoxy resin modified PNP-NS showed a greater decrease than that of the epoxy resin modified by PNP compared with the pHRR and THR data of the unmodified epoxy resin. The corresponding temperature at the maximum heat release rate of the epoxy resin modified by PNP-NS was earlier than that modified by PNP by 10 oC, possibly because that nickel could catalyze the formation of char residue during the thermal decomposition process of epoxy resin and reduce the rate as well as the amount of combustible gas release. SEM analysis of char residue revealed that the epoxy resin modified by PNP-NS generated more effective barrier than that modified by PNP, indicating that the former was a more effective barrier against the exchange of heat and oxygen between the external environment and the matrix. The Raman test results revealed that the char residue of epoxy resin modified by PNP-NS had a smaller size of carbonaceous microstructures than that modified by PNP, which demonstrated that the former have a higher flame retardant efficiency in the combustion process. We can see from the SEM and Raman results that the epoxy resin modified PNP-NS could form a more excellent char layer by the the catalytic of metal than that modified by PNP, demonstrating that the former have a better flame retardant performance. The epoxy resin modified by the PNP had a more excellent performance in the LOI testing than that modified by the PNP-NS. Considering that the epoxy resin modified by the PNP-NS could apparently reduce the pyrolysis/combustion action, higher final char yield as well as higher quality of char residue than that modified by the PNP. So, we can conclude that the epoxy resin modified by the PNP might play a role in gas phase flame retardant and the the epoxy resin modified by the PNP-NS might play a role in condensation phase flame retardant.