Flame-retardant And Smoke-suppressing Application Of Carbon-based Hybrid Materials In Flexible Poly (Vinyl Chloride)

Polyvinyl chloride?PVC?,one of the five generic plastics in the world,has been widely applied in various industries due to its properties such as non-flammable,corrosion-resistant,insulating and good isolation.However,the additives in the processing of PVC make it easy to burn,generating a large amount of smoke,toxic and corrosive gases,which poses a threat to people's lives and property.Therefore,PVC must be flame-retarded and smoke-suppressed.Recently,carbon-based materials have attracted extensive attention of researchers in the flame-retardant field due to their electrical conductivity,heat resistance,chemical resistance,surface and interface properties.In this paper,activated carbon spheres supported NiCo₂?CO₃?_1.5?OH?₃?ACS@BNCC?and ammonium phosphate/reduced graphene oxide?ANP/RGO?hybrid materials were prepared based on different carbon-based materials.Afterwards,ACS@BNCC and ANP/RGO were used as flame retardants in PVC to study the flame retardant,smoke suppression and mechanical properties of PVC composites.The flame-retardant mechanisms of two carbon-based hybrid materials were analyzed.Specific work is as follows:Part ?:Synthesis of ACS@BNCC hybrid material and its flame-retardant application in PVCThe ACS@BNCC hybrid material was successfully prepared by hydrothermal and precipitation reaction and its morphology,structure and thermal stability were characterized.The results showed that ACS@BNCC with a core-shell polycrystal structure had good thermal stability.Among them,ACS as a core exhibited very smooth spherical morphology with a uniform particle size of approximately 2?m,and there are carboxylate,hydroxyl and phospholipid groups on its surface.BNCC nanowires as a shell were evenly dispersed on the surface of the ACS and the thickness was about 50-100 nm.ACS@BNCC and1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid?[BMIM]PF₆?were added to PVC according to different mass ratios,and the flame retardant and smoke suppression properties of PVC composites were tested by limiting oxygen index?LOI?and cone calorimetry test?CCT?.The results showed that the combination of 15%ACS@BNCC and2%ionic liquids?ILs?made the PVC composites have the best flame retardant and smoke suppression properties.The LOI value of 2%ILs-ACS@BNCC/PVC composite reached29.1%,and the peak heat release rate?PHRR?,peak smoke release rate?PSPR?and total smoke production?TSP?were reduced to 63.2%,37.8%and 54.8%of pure PVC,respectively.The flame retardant mechanism of 2%ILs-ACS@BNCC was proposed by analyzing the thermogravimetric?TG-DTG?and char residue results of PVC composites.2%ILs-ACS@BNCC combined a variety of flame retardant effects such as physical barriers,catalytic carbonization and cooling effects,and played a major flame-retardant effect in the condensed phase.In addition,the SEM results of the fractured surfaces of PVC composites showed that ionic liquids improved the dispersion of ACS@BNCC in the PVC matrix.Therefore,the tensile strength,elongation at break and impact strength of2%ILs-ACS@BNCC/PVC were significantly improved compared to ACS@BNCC/PVC.Part ?:Synthesis of ANP/RGO hybrid material and its flame retardant application in PVCThe ANP/RGO hybrid material was successfully prepared by one-step solvothermal reaction and its morphology,structure and thermal stability were characterized.The results showed that ANP/RGO had good thermal stability.Most of the oxygen-containing groups on the surface of RGO were removed,and sheet-like ANP and pleated RGO formed a"sandwich"structure.ANP/RGO hybrid material was applied to PVC according to different mass fractions,and the flame retardant and smoke suppression properties of PVC composites were tested by LOI and CCT.The LOI of 15%ANP/RGO/PVC composite was 27.0%,and the PHRR,PSPR and TSP were 99.1 kW/m²,0.15 m²/s and 21.2 m²,which were reduced to30.1%,40.5%and 50.2%of pure PVC,respectively,indicating that 15%ANP/RGO was an effective and flame retardant smoke suppressant for PVC.The flame retardant mechanism of15%ANP/RGO was proposed by TG-DTG test,SEM and Raman analysis of char residue of PVC composites.15%ANP/RGO combined a variety of flame retardant effects such as physical barriers,catalytic carbonization,endothermic and dilution effects,and played a major flame-retardant effect in the condensed phase.In addition,the effects of flame retardants on the mechanical properties of PVC were investigated by tensile and impact tests.The tensile strength,elongation at break and impact strength data of PVC composites showed that the mechanical properties of 15%ANP/RGO/PVC were not reduced compared to pure PVC.