Study On Synergistic Effect Of Active Carbon On Intumescent Flame Retardant Ethylene-vinyl Acetate Copolymer Rubber

Ethylene vinyl-acetate compolymer rubber?EVM?is a copolymer of ethylene with a high vinyl acetate content?40-80%?and is wildly used for electric wire,cable,rubber roll,household appliances,and automotive rubber parts due to its good heat-resisting,ozone-resisting,and weather-proof properties.To meet the application of fire safety field,such as oil platform,rail transit,electric power communication,building and ships,the research of flame retardant rubber like EVM was necessary.The intumescent flame retardant which is none of melting and dropping,low smoking,and low toxicity develops rapidly.The study of synergist which can improve the efficiency of flame retardant and integrated performance is one of the hot topics of intumescent flame retardant.Compared with new carbon materials such as carbon nanotubes?CNTs?,graphene which has excellent synergistic effect,active carbon?AC?has advantages of simple preparation,environmental protection,low cost,and high specific area.Therefore,the research of synergistic effect of AC in intumescent flame retardant EVM has significant application and theory value for green,low cost,and high synergistic effect intumescent flame retardant.An intumescent flame retardant EVM was prepared based on ammonium polyphosphate/dipentaerythritol as intumsent flame retardant and plant based AC,metal oxides supported on AC?AC-MO?,and recombination of AC and metal phosphate?AC/MP?as synergist.The effect of synergists on vulcanization,thermostability,combustion,and mechanical properties of flame retardant EVM was studied.Meanwhile,the acting mechanism of AC was also studied.The synergistic mechanism reveals that the formation of percolation network structure and catalysis charring effect.The main research achievements are as follows.?1?Planted based AC was prepared via alkali activation.The BET surface area of AC was 1798.3 m²/g due to its high developed hole structure.AC with the particle size of 5¹0?m was dispersed well in intumescent flame retardant EVM.The analysis of vulcanization swelling measurement indicated that IFR and AC did not affect the processability and scorch safety,bud significantly increased the maximum torque of flame retardant EVM,the interaction of additives was enhanced,the nonpolar solvent resistance and cross linking degree of flame retardant EVM was also improved.The study of thermal behavior revealed the thermal stability and glass-transition temperature of flame retardant EVM was improved.The combustion test results confirmed the synergistic effect between IFR and AC.When the mass ration of IFR and AC was 37:3,and the addition was 40 wt%,the LOI value was33.6%,which was higher than that of without AC.The cone test proved that the heat release decreased significantly.The tensile strength of flame retardant EVM improved with the increasing of AC,while the elongation at break decreased.?2?The reasons for synergistic effect of AC were percolation and catalysis charring effect.As the result of vulcanization and rheological properties tests,the maxium torque and viscosity was improved with the adding of AC.From this,a network structure which prohibited the transfer of heat and mass during combusition was formed.The in-situ FTIR and TG-FTIR results indicated that AC accelerated the deacetylation and chain scission of EVM,which led to the formation of cross linking precursors unsaturated carbon double bonds.Besides,the catalysis charring effect of AC accelerated the release of NH₃ and H₂O during the thermal decomposition of IFR,and reduced the volatilization of decomposition products at higher-temperature stage.The study of condensed phase product,X-ray photoelectron spectroscopy and Raman spectrum results further confirmed the mechanism of AC.AC improved the amount and compactness of char residue of flame retardant EVM,the content of C-O-P structure in the char increased which means the degree of cross linking increased.Besides,the degree of graphitization was also improved.?3?The percolation effect of three kinds of palnted AC was studied systematically which was compared with CNTs.The prepared bamboo based AC?AC-1?,paddy bran based AC?AC-2?and bamboo leaf based AC?AC-3?were micrometer-scale random particle,and the BET surface area were 945²088 m²/g because of the high developed hole structure.The results of vulcanization,rheology,thermal analysis,mechanical and combustion properties displayed the percolation effect of AC and CTNs increased the maximum torque,shear viscosity,flow activation energy,intial decomposition temperature,tensile strength,and decreased heat release rate.The percolation effect intensity sequence of carbon materials was:CNTs>AC-2>AC-1>AC-3.As the result of the combination of the texture properties of carbon materials and the percolation effect intensity,the sequence of the influence of the texture properties of carbon materials on percolation effect was:morphology>BET surface area>volume average diameter?D?>molar ratio of C to O on the surface.To increase the BET surface area and decrease D were conductive to improve the percolation effect of AC which might improve various properties of flame retardant EVM.?4?With the excellent catalytic synergistic flame retardancy of metal oxide?MO?and its effect of improving the thermal ageing property as well as the porous and large specific surface area characteristic of AC,a series of metal oxide?Fe₂O₃,CuO,ZnO?supported on active carbon?AC-MO?synergist were prepared by solvent evaporation method.The results of XRD,N₂ adsorption test,and SEM showed that MO with the particle size less than 1?m was dispersed well on the surface of AC.The load of MO on AC were 18.2¹9.3 wt%.MO blocked part of micropore of AC which led to the decreasing of BET surface area and increasing of average pore size.AC and AC-MO had a uniform dispersion in the flame retardant EVM.The research of vulcanization,combustion,and thermal behavior showed the percolation effect of AC-MO improved the maximum torque,flame retardancy,char residue,and the ntegrity and compactness of char residue.The optium synergistic effect was achieved for AC-Fe₂O₃.The LOI value of EVM/37IFR/3AC-Fe₂O₃ was 34.1%,which was higer that that of EVM/37IFR/3AC?33.6%?.The heat resistance,oil resistance,and swelling equilibrium results indicated that AC-MO improved the tensile strength of flame retardant EVM due to the increasing of cross linking density,while the elongation at break decreased.?5?To utilize the catalysis charring synergistic effect of metal phosphate?MP?,and simplify the preparation technology,AC was recombined with MP?AC/MP?.Thus,the decreased of BET surface and percolation effect of AC which might lead to the reduction of general properties of materials could be avoided.The results of vulcanization showed that AC/MP accelerated curing speed and decreased maximum torque slightly.The combustion test confirmed that the excellent synergistic effect of AC and MP improved the flame retardance of EVM,and FeP performed the best.The LOI value of EVM/37IFR/3AC/1FeP was 34.9%.The TGA results indicated MP improved the char residue of flame retardant EVM,the sequence of the improving of char residue was CuP>FeP>ZnP.With the analysis of the char after CONE test,the char residue after combustion of EVM/37IFR/3AC/1FeP system had the best integrity.The heat and oil resistance properties of EVM/IFR/AC/MP system was similar with EVM/IFR/AC-MO system,the adding of AC/MP improved the heat and oil resistance properties of flame retardant EVM.Compared the overall performance of EVM/37IFR/3AC-Fe₂O₃?EVM/37IFR/3AC/1FeP,the former performed better.