Synthesis And Mechanism Research Of Phosphoramide Flame Retardant Based On Biomass Monomer

Due to its own structure,polymers are mostly flammable,and flame retardants are essential additives in the use of polymer materials.With the improvement of people's awareness of environmental protection and the advancement of science and technology,bio-based flame retardants have gradually become a research focus of flame retardant technology.In this paper,three kinds of phosphoramide flame retardants were synthesized by using biomass monomers cytosine(Cy)and furfurylamine(FA),which were used to improve the flame retardant performance of the bio-based polymer material polylactic acid(PLA).The specific research content is as follows:(1)A high efficiency phosphoramide flame retardant PN was prepared by reacting Cy with diphenylphosphinoyl chloride(DPPC).The structure was characterized by nuclear magnetic resonance(NMR)and Fourier infrared spectroscopy(FTIR),and the thermal stability was analyzed by thermal gravity analysis(TGA).The flame retardancy of PLA / PN composites was studied by vertical combustion test(UL-94),limiting oxygen index test(LOI)and cone calorimeter test(Cone).The results show that 0.5 wt% PN can make PLA/PN composites achieve UL-94V-0 rating,and the LOI is increased from 20.6 vol% to 30.4 vol%.The coupling techniques of TGA linked with FTIR(TG-IR),infrared thermal imager,and the Quadra pole-time of flight mass spectrometer(Q-TOF)were used to study the flame retardance mechanism of PN and the degradation behavior of PLA/PN composites.The flame retardant mechanism analysis showed that PN catalyzes the degradation of PLA and improves the flame retardancy by melting-away mode.Meanwhile PN delays the degradation of PLA oligomers into flammable gases which is helpful for extinguishing flame.In addition,by adding the chain extender 1,3,5-triglycidyl-S-triazinetrione(TGIC),the mechanical properties of PLA/PN composites were improved.(2)Two flame retardants,POFA and BPOFA,were prepared by using FA and DPPC and phenylphosphoryl dichloride(PPDC)respectively.Their structure and thermal stability were characterized by NMR and TGA.According to UL-94 and LOI tests,it is found that BPOFA has higher flame retardancy.Adding 1.0 wt% BPOFA can make PLA/BPOFA composites achieve UL-94V-0 rating,and the LOI is increased from 20.3 vol% to 28.0 vol%.However,POFA needs to add 7.0 wt% to make the composite reach UL-94V-0 level,and the LOI is only increased to 26.2 vol%.The flame retardant behaviors of PLA/POFA composites and PLA/BPOFA composites were compared by TGA,Cone and Q-TOF,and the flame retardant mechanism was further studied.The study found that the flame retardant mechanism of POFA and BPOFA is similar to that of PN.The differential scanning calorimeter(DSC)was used to compare the effects of POFA and BPOFA on the crystallization properties of PLA.It was found that PLA/BPOFA composites have better crystallization ability.The Avrami equation and Lauritzen–Hoffman–Miller method were used to further study crystallization kinetics.The results found that a certain amount of BPOFA can provide heterogeneous nucleation point in PLA and make it to crystallize easily.