Study On Synthesis Of Phophinate Flameretardants And Their Application In Flame Retardant PA6

As a common engineering plastic with excellent overall performance,polyamide 6(PA6)is widely used in transportation,electrical,electronic and other fields.Meanwhile,PA6,as the organic polymer material,is flammable and has high heat release in the combustion process,especially a large amount of flaming droplets,which increase the risk of fire spread.Therefore,the development of comprehensive performance flame retardant PA6 has a very important significance for expanding its scope of application and increasing the use value for products.Phosphinates has excellent stability due to its chemical bond of C-P.And because of high flame retardant performance,low smoke,non-toxic,low impact on the physical and mechanical properties of materials and other advantages,phosphinates are widely used as flame retardants in epoxy,polyester,polyurethane,polyolefin,nylon and other polymer materials.This paper is mainly based on the reactions of phenylphosphinic acid(PPA),2-carboxyethylphenyl phosphinate(CEPPA),aluminum hydroxide(ATH)and melamine(MEL)to prepare four novel flame retardant phosphinates:Phenyl phosphinate aluminum(ALPP),2-carboxyethyl phenyl phosphinate aluminum(ALCEP),phenyl phosphinic acid melamine salt(PPM),and 2-carboxyethyl phenyl phosphinic acid melamine salt(MCEP).Structural characterization and analysis is studied by infrared spectroscopy(FTIR),nuclear magnetic resonance,elemental analysis,thermal gravimetric analysis(TG)and other methods,which proves that the structural features of various products have a consistent structure that we expect.The superior flame retardants MCEP and ALPP are chosen to apply in PA6,to study their flame retardancy,mechanical properties and discuss flame retardant mechanism.2-carboxyethyl phenyl phosphinate melamine salt(MCEP)and the epoxy resin coated aluminum phosphinate(EAP)are added to PA6,and flame retardancy,thermal stability and mechanical properties of PA6,are studied by vertical flame test,limiting oxygen index(LOI),thermal gravimetric analysis(TG)and other methods.The results show that it will be a significant breakdown phenomenon when the amount of the flame retardant is added over 10%,so it should be appropriate to reduce the amount of the flame retardant.Added 4.5%MCEP and 4.5%EAP could achieve relatively good flame retardancy,LOI is up to 28.4%,but could only reach UL94 V-2 level in the vertical burn rating.After added MCEP flame retardant compound system,thermal stability of PA6 material has been significantly improved,meanwhile it exhibits good mechanical properties.Phenyl phosphinate aluminum(ALPP)as the main flame retardant,melamine cyanurate(MCA)and zinc borate(ZB)as flame retardant synergists are added to the nylon 6 which contains 30%glass fiber.Flame retardancy,thermal stability and mechanical properties of glass fiber PA6(GFPA6)are studied by vertical flame test,limiting oxygen index(LOI),thermal gravimetric analysis(TG)and other methods.The results show that when adding 12%ALPP,6%MCA and 3%ZB,it reduces the initial decomposition temperature of GFPA6 compare to simply adding ALPP flame retardants,and further enhances the quality of the residual.Flame retardancy of GFPA6 preferably up to UL94 V-0 level,LOI is up to 31.2%,and mechanical properties are well maintained.Flame retardant mechanism of complex system mainly based on ALPP is preliminary studied by thermogravimetric and FTIR interconnection(TG-FTIR),pyrolysis gas chromatography mass spectrometry(Py-GC-MS)and scanning electron microscopy(SEM).The results show that phosphorus-containing compounds haven't been found in vapor lysates of ALPP complex system applied in GFPA6,which indicates ALPP and MCA complex flame retardant system plays a major role in the condensed phase,improving the amount of carbon residue and promoting carbon layer formation.Porous foam layer generates in the surface of the burnt material,insulating heat and oxygen,effectively cutting off the heat transferring.While adding ZB,it further promotes generating of carbon layer,the surface layer of porous foam becomes increasingly dense,which could protect GFPA6 base and played the role of slowing the spread of heat and oxygen.