Synthesis And Performance Study Of Halogen-Free Copolymerized Flame Retardant Polyamide 1210

Except for sharing the excellent properties of ordinary polyamides including high strength,wear resistance,and self-lubrication,long carbon chain polyamide 1210（PA1210）also displays low water absorption,good toughness,and good dimensional stability.Thus,it is widely used in the automotive industry,rail transportation,electronics and electrical appliances,etc.However,similar with most polymers,PA1210 is easy to burn when exposed to open fire,and the poor flame retardant performance also limits the expansion of the application field of PA1210.As a halogen-free and efficient reactive flame retardant,2-carboxyethyl phenyl phosphinic acid（CEPPA）has been applied to the research of flame retardant modification of polyester or short carbon-chain polyamides,but the application in the flame retardant modification of long carbon chain polyamide is rarely reported.In this study,the flame retardant CEPPA-DDA salt（CDS）with high thermal stability and good reactivity was synthesized by modifying CEPPA with1,12-Dodecanediamine（DDA）;then CDS,DDA and sebacic acid（SEA）were copolymerized to prepare copolymerized flame retardant polyamide 1210（FRPA）with different CDS contents,and FRPA was tested and characterized.The details of the study are as follows:（1）The molecular structure of CDS was identified by using fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance hydrogen spectroscopy（1H-NMR）and elemental analysis（EA）.It was found that the reaction conditions for the best yield of CDS were as follows:n_（CEPPA）:n_（DDA）was equal to 1:1.05,and the reaction was carried out at 65℃for 6 h.The thermal stability of CDS near 280-290℃ which is the polymerization temperature of FRPA is much higher than that of CEPPA.The solubility of CDS in water at 25℃ is 45.65 g/100g and the pH of 0.1 mol/L aqueous CDS solution is 7.28,which shows weakly alkaline and is favored for the polymerization of FRPA.（2）FRPA with different CDS contents were prepared by melting polycondensation.The FTIR and ¹H-NMR results of the samples proved that CDS was copolymerized into FRPA macromolecular chain by chemical reaction.Both FRPA and PA1210 were mainly inα-crystalline form,but CDS played a role in hindering the grain growth.The T_5%of FRPA-7 is 390℃,which is 24℃ lower than that of PA1210,and the tensile strength is 38.62MPa.The introduction of CDS reduces the thermal stability and mechanical properties of FRPA,but FRPA can still maintain overall high performance.Although the water absorption of FRPA-7 is higher than that of PA1210,the saturated water absorption of FRPA-7 is only 0.91%,which is still significantly lower than the saturated water absorption of short carbon-chain PA such as 10%for PA6 and 7%for PA66.（3）The flame retardant properties and flame retardant mechanism of FRPA and PA1210 were characterized and analyzed.CDS is effective in improving the flame retardant properties of FRPA.The FRPA with CDS addition of 5 wt%can pass the V-0 grade of the vertical combustion test.Furthermore,the LOI was improved from 22.6%of PA1210 to 30.2%of FRPA-7.CDS plays a synergistic role in flame retardant FRPA in both gas phase and condensed phase.The pyrolysis process of FRPA-7 and PA1210 is similar,but the gas phase products of phosphate compounds containing P=O and P-O-N structures can be observed near 1280 cm^-1and 1077 cm^-1in the TG-FTIR curve of FRPA-7 peak.CDS has a good effect in inhibiting the heat release of FRPA.Compared with PA110,the peak heat release rate and total heat release rate of FRPA-7 were reduced by 24.11%and 9.40%,respectively.The addition of CDS will lead to incomplete combustion of FRPA.The total smoke emission and carbon monoxide generation rate of FRPA-7 were increased by 2.1 times and 1.41 times higher than those of PA110,respectively.In addition,the I_G/I_Dimproved from 0.31 of FRPA-3 to 0.37 of FRPA-7,indicating that the addition of CDS could improve the compactness and graphitization of the residual carbon of FRPA.In this study,we applied the novel halogen-free flame retardant CDS to the flame retardant modification of PA1210 by copolymerization,and the prepared FRPA exhibits excellent flame retardancy,which is expected to further expand the application range of PA1210.