Study On Flame Retardant And Smoke Suppression Of PET And Fiber By Fe₂O₃ Synergistic New Phosphorus-containing Silicone?PDPSI?

Polyethylene terephthalate?PET?has excellent physical and chemical properties and has been widely used in the various fields,such as film,packaging materials,synthetic fibers.However,PET has a low limit oxygen index?LOI?and belongs to flammable polymer material,generating a large amount of black smoke during combustion.Therefore,it is very important to simultaneously improve the flame retardancy and smoke suppression of PET for people and the environment.In order to reduce the environmental hazard from the flame retardant,a halogen-free of phosphorus-containing silicone flame retardant-Poly N-N dimethylene phosphate amidopropyl siloxane?PDPSI?was firstly prepared according to Mannich reaction.The morphology,structure and thermal stability were characterized by infrared?FTIR?,nuclear magnetic resonance spectroscopy?¹H NMR?,scanning electron microscopy?SEM?,elemental analysis?EDS?and thermogravimetric analysis?TGA?.The results showed that,the initial decomposition temperature of PDPSI was 261°C,which satisfied the processing temperature of PET material,and the char residue amount was as high as 62.2%at 700°C,indicating that it owned good charring ability.And the PDPSI/PET composites were prepared by melt blending.The research on the flame-retardant properties of PDPSI/PET composites demonstrated that,when the loading of PDPSI was 5%,the PDPSI/PET composites had LOI value of 27.3%and passed the V-0 rating of vertical combustion?UL-94?.The char residue amount of the PDPSI/PET compositew at 700°C was 17.0%,which was 26.9%higher than that of pure PET.The results of cone calorimeter?CCT?test showed that,PDPSI significantly reduced the heat release rate peak?PHRR?,total heat release?THR?,total smoke production?TSP?value of PET composites.When the content of PDPSI was 3%,HRR,THR and TSP value decreased by 71.19%,29.06%and22.92%respectively,which significantly improved the flame retardancy of PET composites.In order to simultaneously improve the flame retardancy and smoke suppression of PET composites,PDPSI and ferric oxide?Fe₂O₃?were then used to synergistic flame-retardant PET.The flame-retardant test results revealed that,when the addition amount of PDPSI/Fe₂O₃ was 2%and the mass ratio of PDPSI to Fe₂O₃ was 1:2,the LOI value of PDPSI/Fe₂O₃/PET composite material was27.9%,reaching the flame-retardant level,and passed the V-0 rating in the UL-94test.And the PET composite had a char residue content of 17.5%at 700°C,which was an increase of 30.6%compared to pure PET.In the CCT test,the addition of PDPSI/Fe₂O₃ significantly reduced the PHRR,THR and TSP value of the PET composites,and the HRR and THR decreased by 66.05%and 14.3%respectively.The TSP value decreased from 14.4 to 8.1 m²,with a decrease of 43.8%.These implied that PDPSI/Fe₂O₃ simultaneously improved the flame retardancy and smoke suppression of PET.The flame-retardant mechanism of PDPSI/Fe₂O₃/PET composites was studied by SEM,EDS and FTIR.The results demonstrated that the mechanism was,on the one hand,under the co-catalysis of Fe₂O₃ and phosphoric acid decomposed by PDPSI,the PET matrix formed a continuous and dense cross-linked carbon layer.This effectively isolated the heat transfer and flue gas escape during combustion.On the other hand,Fe₂O₃ particles can catalyze the oxidation of smoke precursors to CO₂,further reducing the flue gas production.Therefore,the flame retardancy and smoke suppression of PET were significantly improved.Finally,PDPSI/Fe₂O₃/PET flame retardant fiber was prepared by melt spinning method.The loading of PDPSI/Fe₂O₃ composite flame retardant was0.3%,0.6%,0.9%.And the microstructure,aggregate structure,flame retardancy and tensile properties of PET composites fiber were analyzed.The results showed that,when the flame retardant was added at 0.9%,the LOI value of PDPSI/Fe₂O₃/PET flame retardant fiber increased from 20.4%to 26.7%and passed the B1 grade.In the CCT test,the PHRR,THR and TSP value of the PET composite fiber has reduced by 32.2%,47.2%and 61.3%respectively.In the tensile test,the breaking strength of the PET composite fiber reduced by 18.30%,which can meet the use requirements.