| In this thesis,an intumescent flame-retardant C/P/N system was constructed and applied to the flame retardance of polylactic acid(PLA)and polyolefin.Through the evaluation of artemia experiments,three types of flame retardants with low toxicity and friendliness were selected,including polydopamine modified carbon nanotubes(PDA-CNT),ammonium polyphosphate(APP),and hydroxypropyl methyl cellulose(HPMC),which were combined into the matrix to prepare flame retardant polymer composites.The comprehensive evaluation was conducted on the combustion characteristics,thermal properties,and mechanical properties of the composite materials.(1)The toxicity of various flame-retardant related reagents was evaluated through the Artemia experiments,and the changes in Artemia activity and lethality of three of them(PDA-CNT,APP,and HPMC)under different feeding ratios in the culture medium were investigated.It was confirmed that both the flame retardant and PLA were non-toxic and friendly to Artemia.(2)PDA-CNT was prepared by adjusting the p H value to allow dopamine to undergo oxidative self polymerization on the surface of carbon nanotubes(CNTs).The specific gravity of the coverage of polyamine(PDA)on the surface of CNTs was analyzed by thermogravimetry,and the characteristic functional groups in the composite were characterized by infrared.The surface morphology and pore structure of PDA-CNT were analyzed by transmission electron microscope and specific surface area tester.The results show that PDA can successfully cover the surface of CNT through self polymerization,with a content of about 11.1%.(3)Based on the fact that three flame retardants and PLA are non-toxic and friendly to artemia,a C/P/N flame retardant system was constructed Through Cone Calorimetry Testing,it was confirmed that the main flame retardant indexes(peak heat release rate(PHRR),total heat release rate(THR),peak smoke release rate(PSPR),total heat release(THR)etc.)of PLA composites added with flame retardants such as PDA-CNT,HPMC,and APP decreased by 30% to 50.0%,effectively reducing the heat and smoke release of the composite during combustion,and reducing fire risk.The results show that flame retardant PDA-CNT can reduce heat release,smoke emission,and weaken combustion droplets.In PLA/APP/PDA-CNT composites,PHRR decreased by 46.7%,THR decreased by 33.4%,PSPR decreased by 78.6%,and TSP decreased by 62.9%.HPMC has excellent charring effect,which can effectively improve the amount of residual carbon during the combustion of composite materials,forming a dense carbon layer: The amount of residual carbon in PLA/HPMC/APP composite materials has increased by a maximum of 71.0%,while the surface of residual carbon after combustion expands and the inner layer is dense.Adding HPMC and PDA-CNT to PLA also has a certain flame-retardant effect.Compared with PLA/HPMC,0.5 wt% PDA-CNT composite can reduce the PHRR and TSP of the composite by 64.0% and 43.0%,respectively.(4)The C/P/N flame retardant system has achieved good flame retardancy in PLA matrix,so it was further introduced into polyolefin matrix.In HDPE and PP matrixs,APP/PDA-CNT,APP/HPMC,PDA-CNT/HPMC also exhibit a certain flame-retardant effect.APP/PDA-CNT can synergistically inhibit heat release during the combustion of HDPE and PP.Based on the flame retardancy of APP,the synergistic effect of 0.75 wt% PDA-CNT can reduce the PHRR of HDPE based and PP based composites by 18.9% and 5.4%,respectively.The combination of APP/HPMC also has a significant synergistic effect.Adding 5 wt% HPMC and 15wt% APP to HDPE and PP respectively,the PHRR of the composites was further reduced by 36.6% and 25.0%,respectively.The combination of the two can also increase the carbon residue of PP based composites by 129.0%.Compared with PP/HPMC,the introduction of 1.0 wt% PDA-CNT reduced the TSP of PP composites by 14.9%.In HDPE,the synergistic flame-retardant effect of HPMC and PDA-CNT is not significant. |
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