Two Kinds Of Eco-friendly Nano-Flame Retardants: Preparation And Application In Polypropylene And Epoxy

Ternary Zn Ni Al-LDH-CO₃ was synthesized using the homogeneous precipitation method using zinc nitrate?Zn?NO3?2·6H2O?,nickel nitrate?Ni?NO3?2·6H2O?,aluminum nitrate?Al?NO3?3·9H2O?and urea as raw materials.The orthogonal experiment was used to optimize the preparation conditions of C-LDH.Then,the C-LDH was converted to N-LDH using a ion exchange method.The crystal structure,morphology,interlayer distance and thermal stability of various LDHs were measured by XRD,FTIR,TG and SEM.In order to improve the dispersion of C-LDH in polypropylene matrix,azobenzene-4,4'-dicarboxylic acid anion,containing flame retardant elements N and high-temperature self-crosslinking group?N=N?,was utilized as intercalator to modify N-LDH using ion exchange method.Consequently,the interlayer distance of organic-modified LDH?O-LDH?increased to 2.10 nm.The structure,morphology and thermal stability of O-LDH were measured by XRD,FTIR,SEM and TG.O-LDH,as a novel synergistic fire retardant agent with intumescent flame retardant?IFR,mass ratio of APP:PER=3:1?,was incorporated in Polypropylene?PP?to prepare polypropylene flame retardant composites.The dispersion properties,thermal stability,and mechanical properties of PP composites were characterized by XRD,TG,and tensile test,respectively.The XRD results suggest that highly exfoliated O-LDH platelets exist in the PP matrix and the polymorphism of PP remains unchanged.TG results indicate that the introduction of LDHs could improve the thermal stability of PI?PP/IFR?composite,especially for O-LDH.The tensile test results show that the PIOL1 possesses a better mechanical property than that of PIL1 composite.The flame retardancy of PP composites was tested by LOI,UL-94,and cone calorimetry.The results of LOI and UL94 test suggest that there is a synergistic flame retardant effect between LDH and IFR.ThePIOL1 has a LOI value of 29.3%,and achieves the UL-94 V-0 rating.The results of CC indicate that adding the O-LDH can obviously improve the fire retardancy of PI composite.The surface morphologies of char residues formed after cone calorimetry were further investigated by SEM and EDX.The results show that the addition of O-LDH is helpful to the formation of a more compact carbonaceous layer with continuous surface.Simultaneously,EDX data also proves that O-LDH can improve the thermal oxidative resistance of char layer.A novel intumescent flame retardant?PAMA?with nano-layered structure,combining phytic acid?PA,acid source,carbon source?and melamine?MA,gas source?into one molecule,was successfully prepared using a hydrothermal method.The effect of different ratio and temperature on morphologies of PAMA was explored.The result shows that the optimal condition is that n PA: n MA is equal to 1:6 and reaction temperature is 80 oC,which can effectively form uniform and nano-layered structure through self-assembly.The structure and morphology were demonstrated by FTIR,1H-NMR,XPS,SEM,and EDX-Mapping.The thermal stability of PAMA was measured by TG and a char residue of 37.5% can be obtained under 700 oC.The various flame retardant EP composites has been prepared by adding different amount of PAMA into EP matrix using solvent blend method.The dispersion property,thermal stability,and flame retardancy were investigated by SEM,EDX-Mapping,DSC,TG,CC,LOI,and UL-94.The results of SEM and EDX Mapping show that PAMA is well-distributed in epoxy and no aggregation formed.The TG data displays that PAMA can largely increase the thermal stability and char residue of EP?the char residue of EP-6 is 22.98% at 700oC?.The LOI of EP-6 composites is 29.7% and pass the UL-94 V-0 rating.The peak heat release rate and fire growth rate index of EP-6 fall by 63.9%and 62.2%,respectively with adding the 6wt% PAMA.The flame retardant mechanism was also investigated by TG-IR,SEM,and EDX.The flame retardant mechanism of PAMA is mainly condensed phaseflame retardancy.PAMA acts as a barrier to delay the transfer of the heat at the early stages of combustion and then the phosphorus-containing derivatives from PAMA make the flame retardant EP composites rapidly form the intumescent char layer and this char can effectively prevent hot oxygen transfer and interrupt the fuel supply.