Synthesis Of Phosphorus-Nitrogen Flame Retardant And Its Application Of Flame Retardant PA6 Composites

PA6 as an important polymer material,It can be seen everywhere in people's lives,PA6 materials are needed in many fields.But unmodified PA6 is very easy to burn in air,Therefore,it is necessary to modify PA6 with flame retardant.In this paper,three middle phosphorus and nitrogen flame retardants were synthesized by solution polymerization and applied to PA6,The three flame retardants were characterized by elemental analysis,infrared spectroscopy and thermogravimetric analysis.At the same time,we added these three flame retardants to PA6.The flame retardancy of these three flame retardants was tested by vertical combustion test and oxygen index test,The mechanical properties of flame retardant composites were also tested.The flame retardant mechanism of these three flame retardants was analyzed by thermogravimetric analysis,conical calorimetry and scanning electron microscopy.Finally,the changes of apparent activation energy of three flame retardants after adding PA6 were studied by kinetics,and the relationship between thermal stability and flame retardancy of PA6 flame retardant composites after adding flame retardant was investigated.1.A phosphorus-nitrogen flame retardant PAB was synthesized by one-step reaction of phenylenediamine with diphenylphosphatidyl chloride and characterized,The addition of flame retardant to PA6 showed good flame retardancy,When 15% flame retardant was added,LOI value increased by 24.7% compared with pure PA6 by 28.3% in oxygen index test.Vertical combustion level reached V-0 level,the flame retardant effect was good,and the mechanical properties of flame retardant composites had a certain loss.In thermogravimetric test,when 15% flame retardant is added,the residual carbon at 600 oC is 2.9%,and when 20% flame retardant is added,the residual carbon is 8.9%.The regular and compact carbon layer was observed by scanning electron microscopy(SEM).Cone calorimetry showed that the P-THR and P-HRR values of the system were 111.7 MJ/m2 and 614 KW/m2 respectively when 15% flame retardant PAB was added into the system,which decreased by 5.3% and 31.3% respectively compared with pure PA6.The results of kinetic analysis show that the decomposition activation energy of PA6 decreases at different heating rates after adding flame retardant.2.Poly-Schiff Base Formed by One-Step Reaction of p-Phthalaldehyde with Diethylenetriamine and 4,4'-Diaminodiphenylmethane,Then,two new phosphorus nitrogen intumescent flame retardants PED and PDD were synthesized by adding DOPO into Schiff base chain through addition reaction.Two kinds of flame retardants were characterized.Differential scanning calorimeter(DSC)showed that these two flame retardants had good compatibility with PA6.When these two flame retardants are melted with nylon 6,they show good flame retardancy.The ultimate oxygen index(LOI)of nylon 6 composites was 28.7% and 29.3% respectively when the content of nylon 6 was 15%.The residual carbon at 600 oC is 2.32% and 5.19% respectively.The results of cone calorimetry showed that P-HRR decreased by 41.2% and 43.3% respectively after adding 20% PED and PDD.HRR decreased by 17.4% and 24.2% respectively.Scanning electron microscopy(SEM)showed that the surface of carbon slag was dense,and the dense structure prevented heat transfer and protected the inner part of the matrix.Kinetic analysis showed that the decomposition activation energy of PA6 was slightly lower than that of pure PA6 at different heating rates after adding flame retardant.Compared with other two flame retardants,PDD flame retardant composite system shows better stability.