Synthesis Of Phosphorus-nitrogen Flame Retardant And Study Of Its Flame Retardancy In PLA Composites

Polylactic acid(PLA)is an environmentally friendly,non-toxic and biodegradable polymer material with excellent processability.It is called the most promising “green plastic”,which is widely used in China.However,the unmodified PLA belongs to flammable plastics,which limits the wide use in some fields seriously.Therefore,it is particularly important to study environmentally friendly flame retardant modification of renewable resource PLA.In this study,three kinds of environmentally friendly flame retardants with phosphorus and nitrogen groups were synthesized by solution polymerization.The three kinds of phosphorus-nitrogen flame retardants were characterized by elemental analysis,Fourier transform infrared spectrum(FTIR)and Thermo gravimetric analysis(TGA).Then the three phosphorus-nitrogen flame retardants were applied to the PLA resin to analyze the flame retardancy of three prepared composites by vertical burning and Limiting oxygen index(LOI).At the same time,the mechanical properties of the composites were analyzed by impact and tensile tests.Finally,Thermo gravimetric analysis(TGA)and Scanning Electron Microscope(SEM)analysis were carried out to study the flame retardancy mechanism of the three flame retardants.The main research work and conclusions are as follows:1.First phenyl dichloro sphosphineoxid was added to vanillin for solution reaction.Next add the deacid reagent.Then add p-phenylenediamine for polymerization and characterized the synthesis.By Fourier transform infrared spectrum(FTIR)and elemental analysis test,it indicated that phosphorus-nitrogen flame retardant PPV was successfully synthesized.The test results of flame retardancy showed that the addition of PPV made PLA composites have good flame retardancy effect.When 15% flame retardant PPV was added to the system,limiting oxygen index(LOI)test showed that the LOI was 28.2,which was 33.6% higher than pure PLA.And the vertical burning could reach UL-94V-0 rating.Meanwhile,the mechanical properties of the composites decreased slightly but made a small influence.Thermo gravimetric analysis(TGA)showed that the composite had good thermal stability,and the amount of residual carbon at 700? was 10.4%.When 20% flame retardant PPV was added,the amount of carbon residue was 12.3%.A regular,compact carbon layer was observed by Scanning Electron Microscope(SEM),further confirming the good flame retardancy of the composites.2.The solution polymerization technology was used to add p-Phthaldialdehyde,m-Xylylenediamine and m-Phthaldialdehyde,p-Xylylenediamine into the polymerization system,and then the DOPO was introduced to carry out the polymerization reaction.The target product phosphorus-nitrogen flame retardants PPD and PVD were synthesized and the two flame retardants were characterized.The synthesis of flame retardants PPD and PVD were confirmed by Fourier transform infrared spectrum(FTIR).Elemental analysis showed high purity of the product PPD and PVD.The two flame retardants were found to have good compatibility with PLA by differential scanning calorimeter(DSC).The phosphorus-nitrogen flame retardant PPD and PVD showed good flame retardant effect on PLA resin.When the addition amount was 15%,the two PLA composites reached the UL-94V-0 rating,the Limiting oxygen index(LOI)increased to 34.1% and 36.5%,respectively.Carbon residues of the two composites at 700? were 2.6% and 11.2%,respectively.Scanning Electron Microscopy(SEM)observed that the surface of carbon residue was compact and this compact structure well prevented heat transfer,protected the interior of PLA matrix and played a good flame retardant effect,which is consistent with TG and DSC test results.