Preparation Of Magnesium Hydroxide As Fire-retardant And Application In Polypropylene

Recently, influence on environment was an important consideration for the selection offire-resistant in the polymer with the enhanced protection consciousness of people andconsequent promulgation of the laws and regulations about fire -retardant all over the world.For its series excellent merits as well as in agreement to the sustainable development strategy,superfine magnesium hydroxide was increasingly developed. However, most of the currentprocessing methods of magnesium hydroxide had deficiency, for example, long technologicalprocess, high yield cost, exorbitant equipment, difficult filterability, large size and broad sizedistribution, and serious aggregation. Especially, when magnesium hydroxide was blendedwith polymer, its serious aggregation deteriorated the mechanical performances of thepolymer matrix. Therefore, the prapration of superfine and monodispersion magnesiumhydroxide is more practable. In this dissertation, superfine and monodispersion magnesiumwith high purity was prepared via an easy and high efficient. The particle size and itsdistribution, morphology, crystal phase, and thermal behavior of the product werecharacterized through ultrasonic particle size analyzer (UPSA), transmission electronmicroscopy (TEM) and scanning electron microscopy (SEM), X ray diffraction (XRD),Fourier transform-infrared spectroscopy (FT-IR), and thermogravimetry (TG), respectively.Compatibilized PP/Mg(OH)2 blends were prepared by melting compounding, and thefire-resistance, mechanical and rheological properties were investigated.Superfine magnesium hydroxide was synthesized by using magnesium chloridehexahydrate in presence of acetone as precursor and industrial ammon ia as precipitator in thisdissertation. The filtering time, drying time, mean grain size, dispersivity and aggregationwere gradually improved with increasing content of acetone in the mother liquor. In comparison with blank experiments, the filtering time and drying time were drasticallydecreased by 96% and 75% at the level of 80% acetone in the mother liquor, disk-like andmonodispersed ( d 314nm) magnesium hydroxide particles with high purity (that is, impurityof NH4Cl MgCl2 6H2O not to be examined in the products) were obtained.One-step method was adopted to treat the surface of magnesium hydroxide. Namely,1.2 wt% stearic acid of magnesium chloride hexahydrate was added at the time 2.5h after theend of feeding ammonia. The surface property of products was completely translated fromhydrophilicity to hydrophobicity, and the hydrophobicity index of products was up to 100%.Mechanical properties, dispersibility of magnesium hydroxide and interfacial compatibilityof polypropylene/magnesium hydroxide blends were obviously improved when magnesiumhydroxide was surface-treatment. The oxygen index was 27.5% in the case of 90phrmagnesium hydroxide. However, the mechanical performances of blends were seriouslydeteriorated by contrast to pure polypropylene. The Mechanical and fire-retardant propertieswere obviously improved after the addition of hybrid compatibilizer (POE-g-MAH andEPDM-g-MAH), calcium carbonate and halogen-free fire retardant (POP). Elongation atbreak, tensile strength, impact strength and oxygen index of composites was 264.76%,22.34MPa, 48.65 KJ m-2 and 28.2% at the level of 42phr magnesium hydroxide, 15phrhybrid compatibilizer, 40phr calcium carbonate and 8phr POP. The rheological resultsindicated that the addition of hybrid compatibilizer and calcium carbonate did not change theNon-Newtonian pseudoplastic character of blends and all blends displayed theshear-thinning phenomenon.