| PA66 is mainly used in the fields electronic,automotive,aerospace and other industries as one of the most widely engineering plastics.The oxygen index(LOI)of PA66 is 24.0%,and the level of UL-94 only reaches to V-2.The poor flame retardancy properties of PA66 is due to the special carbon amide structure of PA66 which is rich in nitrogen,and the absorbent cotton is easy ignited by melt dripping under fire.At present,the flame retardants for PA66 in the industry mainly contain halogen elements,such as polybrominated diphenyl ethers,bromined epoxy resin,etc.As is known to all,flame retardant materials containing halogen produce a large amount of toxic,corrosive,smoke and gas during combustion,which is easy to corrosion of equipment,bad for the environment,and harmful to human body.So the development of environmental protection,good compatibility,high efficiency,zero halogen flame retardant becomes a hot issue in the field of flame retardant.This paper synthesized four kinds of reactive P-N flame retardant,which was introduced to the main chain of PA66 by polymerization reaction,improving the flame retardant performance of PA66 by essential flame retarded.On the one hand,the harm of human body and environment of halogen elements is avoided by the method,on the other hand,the consistency problem of flame retardant and substrate is solved either.In addition,the durability of the flame retardant can improve because of the effective composition of flame retardant is introduced in the PA66 main chain.Therefore,this article revolves around the synthesis of P-N flame retardant,the preparation of flame retardant PA66,and the thermal stability,flame retardant properties and mechanical properties of PA66.(1)A phosphorous-nitrogen bond and double end carboxyl containing flame retardant namely bis-(4-carboxyanilino)phenyl phosphamide(BCNPO)was synthesized by acylation reaction with 1,4-aminobenzoic acid and phenylphosphonic dichloride.Fourier infrared(FTIR)analysis results show that the BCNPO contains characteristic group P-N-H,nuclear magnetic(NMR)analysis indicates that BCNPO contains hydrogen of benzene ring,amino,carboxyl,mass spectrum(MS)test results show that the relative molecular mass of BCNPO is 396.4,element analysis indicates that the nitrogen and phosphorus content of BCNPO are 7.06,4.27,respectively.And the BCNPO prepolymer was prepared by the reaction between BCNPO with hexamethylenediamine.Then the BCNPO prepolymer was participated in the polymerization reaction of PA66 through replacing equivalently PA66 prepolymer.Finally the BCNPO is grafted to the main chain of the PA66 through essential flame retardance methods to improve the flame retardant properties of PA66.When the contents of BCNPO prepolymer reach to 5wt%.The initial decomposition temperature of PA66 increases 36°C based on 5% mass loss,and the peak decomposition temperature increases 35°C from 437°C.The LOI and UL-94 test results of PA66 reach to 28% and V-0,respectively.Cone calorimetry test results show that the HRR,THR,TSP,COR of flame retardant PA66 drop to 518.30 kW/m2,518.30 MJ/m2,7.48 m2/kg,5.62x10-3 g/s,respectively.Mechanical properties testing results show that the tensile strength,bend strength,bend modulus of flame retardant PA66 decrease 4.0%,12.1%,4.0% from pure PA66 respectively,but the impact strength of flame retardant PA66 increases 4.3% to 7.3 kJ/m2.BCNPO is worked as gas phase to improve the flame retardancy properties of PA66 resin by using cone calorimeter,SEM,and EDX analysis.(2)A P-N synergistic flame retardant monomer namely N-benzoic acid-(ethyl-N-benzoic acid formamide)phosphamide(BNPPO)is prepared by acrylic acid,dichlorophenyl phosphine and 1,4-aminobenzoic acid.FTIR analysis indicates that BNPPO contains feature group P-N-H?O=C-N,NMR analysis results show that BNPPO contains proton of benzene ring,amine,carboxyl,the molecular mass of BCNPO is 452 tested by MS,and element analysis indicates that the nitrogen and phosphorus content of BCNPO are 6.20,6.87,respectively.The preparation of flame retardancy PA66 is processed with(1).The LOI value and UL-94 rating reach to 28 and V-0 respectively when polymerized with 5wt% BNPPO prepolymer.The TCA and DTC results show that flame retardancy PA66 has significantly thermal stability.The initial and peak decomposition temperatures are 373°C and 450°C,respectively.Cone calorimetry test results show that the HRR,THR,TSP,COR of flame retardant PA66 dive to 432.57kW/m2,72.86MJ/m2,7.63m2/kg,5.83 x 10-3g/s,respectively.Mechanical properties testing results show that the tensile strength,bend strength,bend modulus of flame retardant PA66 decrease 8.83%,11.42% and 8.83% from pure PA66 respectively,but the impact strength of flame retardant PA66 composites increases 10% to 7.7 kJ/m2.The flame retardancy mechanism is studied by cone calorimeter and scanning electron microscope yet.It confirms that BNPPO works as gas-phase flame retardancy mechanism.(3)A P-N synergistic flame retardant,poly-N-aniline-phenyl phosphamide(PDPPD)is experimentally synthesized with phenylphosphonic dichloride and 1,4-benzenediamine.The P-N-H,O=C-N groups are confirmed in the main chains by FTIR.NMR analysis results show that the PDPPD contains hydrogen of benzene ring,amide,amino.MS test results show that the molecular mass of PDPPD is 568.3,element analysis indicates that the nitrogen and phosphorus content of PDPPD are 9.3,11.97,respectively.And the essential flame retardant PA66 is polymerized with PA66 prepolymer and PDPPD prepolymer which prepared by PDPPD and adipic acid.The LOI and UL-94 test results of flame retardancy PA66 reach to 28% and V-0,respectively,when the contents of PDPPD prepolymer reach to 7wt%.The TCA and DTC demonstrate that the initial decomposition temperature of flame retardancy PA66 resin is 43°C lower than pure PA66,but the peak decomposition temperature is 36°C higher than pure PA66 when the contents of PDPPD prepolymer reach to 7wt%.Cone calorimetry test results show that the HRR,THR,TSP,COR of flame retardant PA66 decrease to 429.04kW/m2,60.20MJ/m2,6.56 m2/kg,4.47 x 10-3g/s,respectively.Comparing to pure PA66,the testing results show that the tensile strength,bend strength,bend modulus of flame retardant PA66 fall 4.92%,6.68%,4.92%,respectively,the impact strength is higher 6.43% to 7.45 kJ/m2.The flame retardancy mechanism is studied by cone calorimeter and scanning electron microscope,it confirms that PDPPD works as gas-phase flame retardancy mechanism from cone calorimeter.(4)Flame retardancy PA66 composites is polymerized with PA66 prepolymer and P-N flame retardant monomer namely bis-N-benzoguanamine-phenylphos-phamide(MNPPO)which is synthesized with phenylphosphonic dichloride and phenyl-1,3,5-triazine-2,4-diamine.FTIR and NMR reveal that MNPPO contains P-N-H groups.MS test results show that the molecular mass of MNPPO is 496.4,element analysis indicates that the nitrogen and phosphorus content of MNPPO are 28.25?6.24,respectively.The LOI and UL-94 rating reach to 28% and V-0 when polymerized with 5wt% MNPPO prepolymer.And the TCA and DTC results show that the initial and peak decomposition temperature of flame retardancy PA66 are 373°C and 450°C,which decreases 12°C and increases 13°C than pure PA66,respectively.Cone calorimetry test results show that the HRR,THR,TSP,COR of flame retardant PA66 decrease to 424.07kW/m2?69MJ/m2?6.34m2/kg?5.14×10-3g/s respectively.Comparing to pure PA66,the testing results show that the tensile strength,bend strength,bend modulus of flame retardant PA66 fall 4.0%,5.8%,12.5%,respectively,the impact strength in higher 7.3% to 7.51kJ/m2.The flame retardancy mechanism is confirmed by cone calorimeter and scanning electron microscope,implying MNPPO works as gas-phase flame retardancy mechanism on the process of improving the flame retardance of PA66 composites.Comparing the preparation and performance of flame retardant PA66 modified by BCNPO,BNPPO,PDPPD and MNPPO respectively.It can be clearly seen that the flame retardant performance,thermal stability and mechanical properties of flame retardant PA66 were effectively improved.However,BCNPO,BNPPO work as gas phase flame retarded with poor flame retardant efficiency and char forming characteristics,but PDPPD and MNPPO act on gas phase-condensed phase retarded with excellent char forming properties,especially PDPPD flame retardant PA66 has the best char forming ability.Considering the preparation technology,cost,flame retardant efficiency,content of effective component,char forming performance and so on,it can be drawed a conclusion that PDPPD essential flame retarded PA66 has the most excellent comprehensive performance.(5)A flame retardant PA66 composites reinforced with glass fiber(FR GF-PA66)is prepared between glass fiber and flame retardant PA66 master batches,polymerized with PA66 and PDPPD pre-polymers.In presence of 10 wt% PDPPD in FR GF-PA66,the TCA/DTC measurements from 376 to 411°C showed an initial decomposition temperature for FR GF-PA66 of 35°C higher than that of pristine PA66.From 463 to 499°C,the peak decomposition temperature was 36°C larger than that of pure PA66.The LOI and UL-94 test results of FR GF-PA66 reached 29% and V-0,respectively.The flame retardant mechanism is studied by cone calorimeter testing and confirmed that both the HRR and THR decreased significantly.Also,the tensile strength,bending strength,bending modulus,and notched impact strength of FR GF-PA66 reached substantial values of 110.3MPa,118.5MPa,4.78 GPa,and 10.1 kJ/m2,respectively. |
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