Study On Synthesis And Properties Of Melamine-based Phosphorus-containing Flame Retardants

Polyamide 6(PA6)is widely used in the fields of machinery,electronics due to its excellent mechanical properties,electrical properties and corrosion resistance.As an organic polymer material,PA6 has the disadvantage of being flammable,and it will produce toxic fumes and melt dripping during burning,which seriously threatens the safety of life and property.Therefore,it is necessary to improve the combustion performance of PA6.And it is one of the most effective ways to develop the corresponding flame retardant for the combustion characteristics of PA6 to enhance the flame retardancy.In this paper,the intermediate DP was synthesized from o-phenylenediamine and phosphorus oxychloride,and then two novel melamine-based phosphorus-based flame retardants DPMA and DPMS were synthesized by reaction with melamine(MA).The chemical structure of target product was characterized by FT-IR,NMR and EA,the thermal stability was analyzed by TG.The results proved that the structure of the products conformed to the expected design and has good thermal stability.DPMA and DPMS was introduced into PA6 by melt blending,respectively,and the flame retardant and mechanical properties of composites were investigated through limiting oxygen index(LOI),vertical combustion(UL-94),TG,SEM,Raman spectroscopy,cone calorimetry and mechanical properties test.The results showed that DPMA and DPMS can significantly improve the flame retardancy of PA6 composites.The LOI value of PA6 composite with 20wt% DPMA added reached 28.1%,the UL-94 test reached V-1 level,and the amount of char residues at 800 °C was significantly improved.SEM and Raman spectroscopy test showed that the residual char layer had more compact microstructure with higher graphitization degree.The 20wt% DPMS addition of PA6 composite reached V-0 level,and the LOI value was 29.2%,indicating that the same added amount of DPMS had better flame retardancy to PA6 than DPMA.The cone calorimeter results showed that the addition of 20% DPMS reduced the total heat release(THR)of the PA6 composite by 29.3%,the total smoke emission(TSR)by48.9%,and the char yield from 3.6% to 20.3%.And the formation of a fully expanded carbon structure with high graphitization degree,thereby effectively improving the flame retardant performance and reducing the combustion hazards of PA6.