Flame-retardant Smoke Suppression Wood And Ethylene-vinyl Acetate Copolymer Obtained By Magnesium Aluminum Layered Double Hydrotalcite-like

In this work,magnesium aluminum layered double hydrotalcite was directly in situ grown on the inner surfaces of wood vessels in order to obtain flame-retardant and smoke-suppressing wood.phytic acid intercalated layered double hydroxides were used in ethylene-vinyl acetate copolymer via melt compounding method to enhance its'flame-retardant and smoke-suppressing property.XRD,FT-IR,SEM were used to characterize the morphology of in situ growth of LDHs or before and after the interlayer anion changed.The flame retardant,smoke suppression and mechanical properties of materials was characterize by limiting oxygen index,thermogravimetric analysis,heat release rate,smoke release rate,total heat release,total smoke release,impact strength,tensile strength,etc.A novel flame retarding technique was developed for wood through the in situ hydrothermal growth of a hydrotalcite-like compound(MgAl layered double hydroxide,MgAl-LDH)on the inner surfaces of vessels.MgAl-LDH nanosheets were uniformly in situ grown on the inner surfaces of the wood vessels to form spherical aggregates with sizes of about 0.5 to 1 mm.The in situ grown MgAl-LDH sheets in the wood vessels prevented flame combustion and smoke diffusion;this was confirmed from limiting oxygen index(LOI)and the cone calorimeter tests.The results indicated that the LOI of the wood increased from 19 to 48%after the growth of the LDH.The total heat release decreased by 66.17%,and the total smoke production decreased by 77.57%.Mechanical property tests proved that the in situ growth of MgAl-LDH resulted in the wood showing enhanced tensile strength and compressive strength.Obviously,this low cost and efficient method can be used to improve the flame retardancy and smoke suppression of wood without changing its appearance and structure.MgAl-LDH intercalated phytic acid is mixed with ethylene-vinyl acetate copolymer by melt compounding method,and then the thermal stability,flammability and mechanical properties of the composite material are tested.The total heat release of the mixture decreased by 69.78%,the peak heat release rate decreased by 82.93%,and the total smoke produce decreased by 65.86%.Phosphate contained in phytic acid itself synergizes with the flame retardant and smoke suppressive effects of hydrotalcite.By the thermal decomposition of EVA,it can promote the formation of carbon and then form a dense structure of carbides.At the same time,the phosphorus-based flame retardant will form a layer of non-flammable stable compound covering the surface of the burned material,forming a physical insulation layer.At the same time,phytic acid intercalated hydrotalcite has better compatibility with acetic acid-vinyl acetate copolymer.The presence of phytic acid improves the contact between hydrotalcite and EVA to a certain extent,thus enhancing the mixture impact strength.