Preparation And Application Of Lamellar Nano Magnesium Hydroxide As Smoke Suppressor/Carbon Forming Agent

The toxic smoke produced by fire is the first killer threatening people’s life safety,and the cable copper core by high temperature lead to circuit interruption,and bring huge obstacles to disaster relief.Therefore,low smoke flexible fireproof cable has received great attention in recent years.Because of its advantages of low cost and high domestic production,polyolefin has gradually replaced silicon rubber as the common matrix of flexible fireproof cable filling layer material.As the filling layer material of flexible fireproof cable,the ceramic polyolefin material still has the problems of high smoke generation and poor heat insulation.In view of these defects,this paper synthesized nano sheet magnesium hydroxide smoke suppressant and nickel hydroxide/magnesium hydroxide(Ni/Mg)composite carbon agent by hydrothermal method,and applied them to ceramic polyolefin composite material in order to improve the smoke suppressant and heat insulation properties of filling layer material.Furthermore,low melting point fluxing agent was introduced into the composite system to enhance the strength of the ceramic layer formed after the combustion of the filling material.Main research contents:1、Hexagonal magnesium hydroxide nanosheets were prepared from calcined magnesite by hydrothermal method at 200℃ and reaction time of 12 h in 4mol/L Na OH solution.The raw materials used in this method are cheap and easy to obtain,and the morphology of product is easily controlled by hydrothermal method.The conical calorimetry test was carried out by adding the synthesized nano-flake magnesium hydroxide into the ceramized polyolefin base formula(PE:POE: wollastonite: zinc borate =20:20:54:6,measured by mass percentage).The total heat release was 57.67Mj/m2,and the total smoke generation was 3.88 g.They are all lower than the same amount of H51 magnesium hydroxide commercialized by Arpo.2、On the basis of hydrothermal synthesis of magnesium hydroxide,Ni/Mg composite carbon agent was prepared by adding nickel nitrate into the reactant to carry out hydrothermal reaction.The charge-forming agent has a flower-like lamellar cross structure,and the XRD results show that the crystal phases of nickel hydroxide and magnesium hydroxide are respectively.When the carbon forming agent was introduced into the basic formula,it showed excellent properties of smoke suppression and carbon forming,and the carbon residue rate reached 74.15%.SEM images of carbon residue section show that loose and porous carbon is filled between the skeleton fillers,which greatly improves the heat insulation ability.3、In order to improve the hardness of ceramic layer carbon residue after ceramicized polyolefin combustion,low melting point fluxing agent was introduced into the smoke suppression system and the carbon forming system respectively.The results show that the strength of carbon residue decreases and cracks appear on the surface of carbon forming system after combustion.For the ceramic polyolefin in smoke suppression system,the strength of carbon residue increases and the whole carbon is uniform and compact.The higher the content of fluxing agent is,the higher the hardness of carbon residue is.However,when the content of fluxing agent is more than 13.5,large holes and gaps begin to appear between the skeleton filler,and cracks occur when the content of fluxing agent reaches 18,which is not conducive to heat insulation.Finally,the optimized formula of ceramized polyolefin was obtained: PE:POE: wollastonite: zinc borate: MH: fluxing agent = 15:20:45:6:5:13.5.