| Layered Double Hydroxides (LDHs), being a kind of inorganic flame retardants with high efficiency, non-toxic and low smoke, have attracted an increasing attention in many flame area. LDHs as the inorganic flame retardant in polymers have aroused scientific researcher extremely large interest, but there is still a great distance away from the industrialization, there are a lot of work still needs further research. In the dissertation, a series of LDHs were prepared by low saturated state of coprecipitation and the roasting reconstruction method under microwave-crystallization with short crystallization time and fewer reports in the previous literatures. The thus synthesized samples were selected and applied to polypropylene (PP) and ethylene-vinyl acetate copolymer (EVA) as flame retardants. The doping impact of LDHs content upon flame-retardant properties and mechanical properties of polymers was investigated. Some new and valuable research achievements are described in the dissertation.Nanocrystalline ZnAl-C6H5SO3 LDHs with the particle size of 20-100nm and the good dispersion were fleetly prepared by the technology of the microwave-crystallization and low saturated state of coprecipitation. The thus synthesized sample was applied to PP, the properties of flame retardant in PP was studied in detail by the techniques of scanning electron microscopy (SEM), limiting oxygen index (LOI), cone calorimeter (CONE), and so on. The results show the dispersion of additives in PP is uniform, the LOI of the composite is up to 28. Moreover, it can be found the modified LDHs can reduce heat release rate of PP, and effectively delay and inhibit the smoke release rate of PP.MgAl-C6H5SO3 LDHs was prepared by the roasting reconstruction method assisted microwave-crystallization, and then the MgAl-C6H5SO3 LDHs/EVA composite was prepared by blending the synthesized LDHs and EVA. The flame retardancy and mechanical properties of the MgAl-C6H5SO3 LDHs/EVA composites with different content of MgAl-C6H5SO3 LDHs were studied. The thermal gravimetric analysis (TGA) revealed that the decomposition of composites in high temperature was promoted with the increase of MgAl-C6H5SO3 LDHs, moreover, the weight loss changes could be neglect in range of 420-500℃. The weight loss curves of composites exhibited the trendency extending to high temperature zone and low temperature zone, respectively, when the addition of MgAl-C6H5SO3 LDHs was 60% and 70%. The results showed that the flame retardancy of the composite was better, and the LOI was 32%, increased by 68.4% when the MgAl-C6H5SO3 LDHs content was 70%.The controllable nano-Mg3Al-WO4 LDHs particles with the particle size of 10-90nm could be swiftly prepared by reconstruction method of the calcined Mg3Al-CO3 LDHs product under microwave irradiation. The thus synthesized sample was applied to ethylene vinyl acetate (EVA) copolymer, the flame retardancy and thermal degradation properties of LDHs/EVA composites were studied in detail by the techniques of limiting oxygen index (LOI), UL-94 vertical burning and thermogravimetric analysis (TGA). The results showed the best LOI value could be increased up to 34% and achieve UV-94V1 when the content of the nano-LDHs in LDHs/EVA composite was 70%. TGA also showed that the thermal stability of the composite was increasing with the LDHs content increasing. LDHs could decrease initial temperature of thermal degradation, and promote char formation of the composite, moreover, the residue mass was increasing with the LDHs content increasing. When the LDHs content was 70%, the carbonaceous residue-shield was up to 59.7%. It was suggested that LDHs could catalyze esterification, dehydration and char formation of EVA.
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