Design And Synthesis Of Cyclophosphamide Flame Retardants And Their Finishing On Polyester Fabric

As the main type of chemical fiber,the annual output of polyester can account for 80%of the total synthetic fiber.Owing to excellent characteristics such as high strength,high elasticity and good wear resistance,PET fabric is widely used in home,industry,automobile,high-speed railway and other fields.However,PET fabric will produce a large amount of smoke and dropping when burning,and it is very easy to cause serious harm,which seriously limits the application of PET fabric.Some studies have shown that phosphoramide structure can catalyze cis-elimination reaction,more easily decompose phosphoric acid compounds,promote the formation of stable char residues,and maintain high thermal stability and less release of volatile substances at high temperature or combustion.On the other hand,the phosphoramides with different substituents showed different flame retardant effects.In this paper,a variety of cyclic phosphoramide flame retardants,polysiloxalkyl cyclophosphamide(PDPTP),4-hydroxyphenyl cyclophosphamide(DPHBP),hydroxy ethyl cyclophosphamide(DPHP)and pentaerythritol hydroxy ethyl cyclophosphamide(PDNP)were designed and synthesized,and then the flame retardants were treated on the fabric by post-treatment technology.The chemical structure of the flame retardant was determined by IR and NMR,and the apparent morphology and element analysis,flame retardancy,thermal stability,combustion behavior,flame retardant mechanism,apparent morphology,element analysis and physical and mechanical properties of the residual carbon after combustion were analyzed.The main research contents are as follows:y-Aminopropyl triethoxysilane(APTES),as an amino functional group siloxane,which contains Si element to increase the carbonization of fabric and provides N element for flame retardant to achieve the purpose of synergistic flame retardant.After finishing with flame retardant PDPTP,the PET fabric passed the vertical combustion test,the LOI value can reach 24.6%,and the damage length can be reduced to 13.2cm.The flame retardant PET fabric is degraded in advance,because with the increase of temperature,the flame retardant first decomposes into metaphosphoric acid and other compounds,which promotes the fabric to degrade into char residues in advance,resulting in a significant increase in the final amounts of residues.At the same time,the heat release of flame retardant PET fabric decreased significantly,and the pHRR decreased by about 48%.Although the smoke release after finishing increased,the increasing trend of smoke release became lower and lower with the increase of the amount of flame retardant,and the purpose of anti-dropping is realized.Moreover,the flame retardant PDPTP can inhibit the combustible ether,hydrocarbon and carbon-based compounds produced during fabric degradation,and reduce the generation of combustible gas CO.Moreover,the tensile force and whiteness of the finished fabric remain basically unchanged.Although the flame retardant PDPTP increases the char property of the fabric,the flame retardant performance is improved less.Based on these theories,4-aminophenol is used to replace APTES.On the one hand,benzene ring structure can provide excellent carbon source for flame retardant.On the other hand,the existence of terminal hydroxyl groups will also enhance the effect of flame retardants.After finished with flame retardant DPHBP,the PET fabric passed the vertical combustion test,the LOI value can reach 25.2%,and the damage length can be reduced to 8.4cm.The flame retardant PET fabric degraded in advance,the final residues increased,the heat release decreased significantly,the pHRR decreased by about 58%,and the smoke release increased.Moreover,DPHBP inhibits the combustible ether,hydrocarbon and carbon-based compounds produced during fabric degradation,reduces the release of non-combustible CO2 gas.Moreover,the tensile force of the finished fabric remains basically unchanged,but it has a great impact on the color of the fabric itself.The benzene ring structure causes the synthesized flame retardant DPHBP to behave as a solid,and the granular flame retardant is adhered to the surface of the flame retardant PET fabric.Although the damage length of the PET fabric is greatly reduced,the increase of LOI is low,and the discoloration of the PET fabric is obvious.Ethanolamine is often introduced as a substituent in the flame retardant industry.On the one hand,the introduction of nitrogen source makes the flame retardant achieve the synergistic effect of phosphorus and nitrogen.On the other hand,2-hydroxyethylamine contains terminal hydroxyl groups,which can produce water during thermal decomposition or ring opening reaction in cyclic phosphate ester,which can effectively improve the flame retardant effect.The LOI value of DPHP flame retardant PET fabric can reach 27.6%and the damage length can be reduced to 7.9cm,while that of PDNP flame retardant PET fabric can reach 30.3%and the damage length can be reduced to 5.1cm.The two kinds of flame retardant PET fabrics were degraded in advance,which promoted the fabric to degrade into char in advance,resulting in a significant increase in the final amount of char residues.The heat release of DPHP and PDNP flame retardant PET fabrics decreased significantly,and the pHRR decreased by about 50%and 49%respectively,but the smoke release after finishing increased.DPHP and PDNP flame retardants inhibit combustible ethers,hydrocarbons and carbon-based compounds produced during fabric degradation,and reduce the generation of combustible gas CO.Moreover,the tensile force and whiteness of the finished fabric remain basically unchanged.In short,this paper solves the problems of flammability and droplet of polyester fabric by surface treatment,and gradually improves the flame retardant performance of polyester fabric through the structural design of cyclophosphamide flame retardant,which lays a scientific foundation and theoretical basis for the structural design of high-performance flame retardant for polyester.