The Preparation Of Ultrafine And Flake Magnesium Hydroxide And The Performance Research Of Flame Retardant Polypropylene

In this paper, direct precipitation was used to prepare magnesium hydroxide flameretardant using light burning magnesium, chloride and ammonia as the main raw material.And then, the dispersion and morphology influence of magnesium hydroxide on thedifferent reaction liquid and hydrothermal modification was studied and three differentkinds of surfactants were used to modify magnesium hydroxide. Next, magnesiumhydroxide independently flame retardant and synergistic flame retardant with associationeffect agent polypropylene were studied. Last, the comprehensive performance of halogen-free flame retardant dynamically vulcanized composite materials was studied.First of all, the influence of synthetic product’s average particle size with the reactiontemperature, reaction time, dosage of ammonia and ammonia water adding speed wasdiscussed. The experimental results showed that the optimum reaction conditions forsynthesis of magnesium hydroxide were the reaction temperature of40℃, the reactiontime of1.5h, the ammonia dosage of170mL and the ammonia water adding speed of12mL/min. The magnesium hydroxide was characterized using FT-IR, XRD, TG and SEMmethods. The results showed that it was ultra thin sheet magnesium hydroxide and hadgood crystal morphology. The influence of magnesium hydroxide on different reactionbottom liquid was studied. The results showed that the preparation of magnesiumhydroxide with stoste had better crystallization property, dispersion performance andcrystal morphology than filtrate. The effect of preparation of magnesium hydroxide on thehydrothermal modification conditions was studied. The experimental results showed thatextending the hydrothermal modification time could improve the morphology ofmagnesium hydroxide and the dispersion performance. What’s more, rising thehydrothermal modification temperature also could improve the dispersion performance.Secondly, the magnesium hydroxide was surface modified by adding three differentkinds of surfactant-PEG, SDBS and PVP for improving dispersion property and microstructure. The sedimentation experiment results and polarizing microscope imagesshowed that PEG had good effect to magnesium hydroxide at lower concentration. WhilePVP and SDBS had best dispersion effect when the adding dosage is respective1.2%and1.5%. The SEM results showed that adding a certain amount of surfactant improved themorphology of magnesium hydroxide, especially the SDBS.Finally, the influence of magnesium hydroxide on the properties of polypropylene wasstudied. It studied gas phase silica（SiO₂） and multi-walled carbon nanotubes（MWCNTs）flame retardant polypropylene cooperated with magnesium hydroxide. Experimentalresults showed that the LOI of the composite material was up to30.6%and attained thelevel of diffcult-flammability when using the carbon nanotube of1%equivalently replacemagnesium hydroxide. The flame retardant property of polypropylene was improved whenadding a certain amount of SiO₂, but the mechanical properties of the composites weredecreased obviously. According to the above situation, compounding MWCNTs with SiO₂cooperated with magnesium hydroxide inflaming retarding polypropylene had two aspectsof advantage, one promoting flame retardant property of polypropylene and two decreasingthe loss of mechanical properties of composite materials.The performance of halogen-free flame retardant dynamically vulcanized PP/EPDM/Mg（OH）₂composite materials was studied. The experimental results showed that thedynamic vulcanization not only increased the mechanical properties but also the flameretardant performance of the composite materials.