Synthesis Of Cyclotriphosphazene Derivatives And Flame Retardant,toughening Of Polylactic Acid

Polylactic acid has great potential to replace traditional petroleum-based plastics with its excellent biodegradability.It is widely used in packaging materials,medical and health,electronics and automotive engineering.However,PLA is extremely easy to burn and generates a large number of molten droplets during the combustion process,which limits its application in many fields.Therefore,It is very important and necessary to study the flame retardancy of polylactic acid materials.Melt blending modification is one of the effective means to overcome the above disadvantages.In this thesis,a flame retardant containing phosphazene and phenanthrene structure was synthesized,and the flame retardant was tested and characterized by infrared,nuclear magnetic resonance and elemental analysis tests.Flame retardant PLA/HABP-DOPO blended materials were prepared by melt blending with PLA as the matrix.The morphology,structure and properties of flame retardant PLA/HABP-DOPO blended materials were studied by various tests and characterization methods.By adding POE,photoinitiator and UV radiation to flame retardant blends,the effects of POE addition and UV dose on the morphology and properties of PLA/HABP-DOPO/TAIC/POE blends were studied.The main research work is as follows:(1)The flame retardant HABP-DOPO was synthesized by addition reaction,and the flame retardant was characterized and tested.Successful grafting of target groups was characterized by FTIR.Functional group access ratios were characterized by NMR.Characterization of flame retardant composition by elemental analyzer.Thermal stability of flame retardants is characterized by TGA.(2)PLA/HABP-DOPO blends with different ratios were prepared by melt blending,and the properties of the blends were characterized and studied.The results show:the LOI value of the composite material increased from 19%to 29%and the vertical combustion performance was increased from NR of pure PLA to V-0 level with the addition of 25 wt%FR.The notched impact strength did not decrease,and the tensile strength and elongation at break decreased by 7.2%and 10%,respectively.In the cone calorimetry test,THR and HRR were effectively reduced,and the carbon layer increased after the material burns,which reduced the degree of combustion.The thermal weight loss test proves that the addition of flame retardants improved the thermal stability of the composites,and the residual carbon increased from 0.026%to14.4%of pure PLA.DSC test proves that the addition of HABP-DOPO increased the glass transition temperature of the material and promoted the crystallization of PLA.Infrared spectrum test proves that there was a hydrogen bonding between flame retardant and PLA.The flame retardant mechanism was analyzed by SEM and EHC.Flame retardant mechanism and solid phase flame retardant mechanism effectively promoted the formation of carbon layer and achieved flame retardant effect.(3)Different blends of PLA/HABP-DOPO/POE/TAIC composites were prepared by melt blending.After different doses of ultraviolet light were irradiated,the properties of POE composites with different blends were studied by testing and characterization.The results show that the addition of UV radiation and photoinitiator TAIC caused a radiation cross-linking reaction between PLA and POE,which increased the impact strength of the blended material from 4.7k J/m~2 to 8.44k J/m~2 at the highest.With the increase of radiation dose,the elongation at break first increases and then decreases,while the tensile strength decreases to a large extent.It was found by SEM that the compositesl were crosslinked by radiation,the interface between POE and PLA material was blurred,the elastomer was stretched and deformed,and some energy was absorbed during the impact,which caused the impact strength to increase.TG tests found that the residual carbon content of the composite increased compared to before the irradiation.DSC tests found that radiation increased the glass transition temperature and cold crystallization temperature of the blended material,the melting temperature changed little,and the crystallinity also increased.