Research And Preparation Of Polyamide-based Flame Retardant And Flame Suppression Materials

With the rapid development of modern society,the use of fuel is becoming more and more widespread.Among them,there is an urgent need to solve the safety issues of the use and storage of diesel,gasoline and liquefied petroleum gas.On the battlefield,in order to prevent the fuel tanks of aircraft,tanks,ships,and other weapons and transportation equipment from being hit by artillery shells,causing "second explosions of fuel" and causing major casualties,it is necessary to reduce hidden oil safety risks.The fuel tanks and tankers of weapons and equipment are filled with flame retardant and anti-explosion materials,which can effectively prevent combustion and explosion when encountering accidents such as open flames and explosion shock waves.The storage and transportation safety of flammable and explosive fuels have always been the focus of attention.During the transportation of fuel oil,static electricity caused by shaking can easily cause explosions and other safety accidents after encountering external factors such as open flames or impacts.Polyamide 6(PA6)is the most representative polyamide polymer widely used,with excellent mechanical properties and high temperature resistance.It is widely used in injection molding and extrusion materials,and has a wide range of production and application prospects in the world.However,due to PA6’s lack of flame retardancy during combustion,a large number of droplets are produced and toxic gases are released.At the same time,PA6 itself has a high volume resistivity,which is prone to the accumulation of static electricity.There are certain security risks in the use process,which limits its application.Therefore,in order to achieve the performance of flame retardant and explosion suppression,flame retardant filler and antistatic agent must be added to PA6.However,when the mature commercial flame retardants make PA6 reach the v-0 fire rating,the added amount needs to reach more than 15%.On this basis,the continued addition of antistatic agents will cause the material to lose its original excellent comprehensive performance due to the excessive content of fillers.This is a military spherical non-metallic flame retardant explosion suppression material,designed a new type of phosphorus and nitrogen(flame retardant formula,and two methods of carbon nanotubes modified,and join the PA6 matrix,flame retardant properties,dynamic mechanical properties and antistatic properties test research,discussed the several factors affect the performance of flame retardant explosion suppression materials explosion-proof,for the industrialization of new flame retardant explosion suppression material production provides the data support.Flame retardant and anti-explosive materials are the key to solve the problems of fuel storage and transportation safety.The research content of this paper mainly includes the following three parts:1.A melamine cyanurate(MCA)and diethylaluminum hypophosphite(OP)composed of a phosphorus-nitrogen synergistic flame retardant system was used as a flame retardant for polyamide 6(PA6),and was prepared by melt blending.Flame retardant PA6 composites,and explored the flame retardant properties of PA6 composites under different ratios of MCA and OP.The results show that there is a good synergy between MCA and OP.The flame retardant efficiency of the two is significantly higher than that of the PA6 composite when added alone,which significantly improves the thermal stability and flame retardancy of PA6.When 3%MCA and 5%OP are added,PA6 composite can reach UL-94 V-0 grade,LOI is 28.1%.While suppressing the dripping,the peak heat release rate and the total heat release are significantly reduced.They fell by 55%and 61%,respectively.On the basis of this flame-retardant formula,with the addition of 8%conductive graphene(CG),PA6 composite materials can still maintain UL-94 V-0 grade,LOI increased to 31.0%,and volume resistivity decreased by 4 orders of magnitude,reaching antistatic standards.2.Graft modification of Multi-walled carbon nanotubes(MWCNTs)with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO),through infrared spectroscopy,thermogravimetric analysis and transmission Electron microscope and other methods have been used to characterize the chemical structure and microstructure of modified Multi-walled carbon nanotubes(DOPO-MWCNTs).DOPO-MWCNTs were then introduced into the PA6 matrix by blending to prepare flame-retardant and flame-retardant PA6 composites.The results show that the PA6 composite with the addition of 3wt%DOPO-MWCNTs has a maximum LOI of 27.5%,and does not generate droplets,and has passed the UL-94 V-0 rating.The heat release rate and total heat release were significantly reduced,from 112 MJ/m2 and 776 kW/m2 to 96 MJ/m2 and 493 kW/m2.At the same time,the CO release from the smoke release rate was also effectively controlled,which decreased by 45%and 48%,respectively.Due to the unique electrical properties and char formation of MWCNTs,the PA6 composite added with 3%DOPO-MWCNTs has a residual carbon content of 6.9%at 700℃,which effectively promotes matrix carbon formation to block oxygen and heat transfer.At the same time,the volume resistivity of the PA6 composite material decreased to 3.1 × 108Ω·cm,reaching the antistatic level.The surface modification of DOPO to MWCNTs improved the dispersibility in the PA6 matrix and maintained the excellent mechanical properties of PA6 itself.3.Using melamine(MEL)and phytic acid(PA)as reactive monomers,graft modification of Multi-walled carbon nanotubes(MWCNTs)by supramolecular self-assembly technology,and then the modified Multi-walled carbon nanotubes(PA-MEL)-MWCNTs)were added to the PA6 matrix by physical blending to prepare flame-retardant PA6 composites.Vertical combustion UL-94,limiting oxygen index(LOI),and cone calorimetry(CONE)tests show that the LOI of PA6 composites with 3%PA-MEL-MWCNTs is increased to 26.8%,which inhibits the droplets from reaching UL-94.V-0 rating.The heat release rate and total heat release were significantly reduced.The THR and pHRR were 96 MJ/m2 and 493 kW/m2,respectively,and the amount of smoke released was effectively reduced,reducing the risk of fire.It was found from dynamic mechanical(DMA)tests that PA-MEL-MWCNTs effectively improved the low-temperature and high-temperature resistance of PA6 composites and improved the thermal stability of the composites.Because the addition amount is small,and the surface modification of MWCNTs by PA-MEL can effectively improve its dispersibility in PA6 matrix,the composite material maintains the excellent mechanical properties of PA6 itself.