Prepration Of LDH Containing Nickel And Investigation Of LDH/EVA Composite

Hydrotalcite is also called layer double hydroxides (LDHs), because of their unique layered structure and adjustability of interlayer anions and layer cations. Therefore, hydrotalcite has been greatly focused on in recent years. It has become a hot aspect in the inorganic flame resistant field. The results of flame resistant show that the combustion of hydrotalcite produces no deleterious and poisonous smoke and gas. It produces no pollution for the environment. At the same time, hydrotalcite itself has the smoke suppression and available rich raw material. Therefore, although the flame retardant studies of hydrotalcite for polymer have been reported, it still needs to take a deep research work because the flame retardant of hydrotalcite with high efficiency cannot be applied in the industrial scale. This dissertation adopted the microwave hydrothermal crystallization coprecipitation with saving time and enegy to rapidly prepare the hydrotalcite containing nickel of surface and interlayer modification. The relationships among crystallinity, mode of action of interlayer anions, morphology, thermal property, surface hydrophobicity of hydrotalcite and modifier and nickel content are explored. The composite of hydrotalcite and Ethylene vinyl acetate (EVA) copolymer was prepared by the melt blending method. Further, the thermostability, fire resistance and mechanical property of composite are studied and discussed in detailed in this dissertation.First, this dissertation investigates the influences of different crystallization method and addition of a small amount of nickel ions on the structure and property of hydrotalcite because of that the different synthesis method and cationic composition of layer have an effect on physicochemical property of hydrotalcite. And then the changes of structure and property of hydrotalcite which leads to the change of the thermal behavior, the flame retardancy and smoke suppression, and the mechanical property of EVA copolymer by thermal analysis, cone calorimeter, LOI and mechanical experiment are explored. The results show that the interactions of both OH--CO32- and CO32--CO32- in Ni0.1MgAl-MHT with microwave aging are weaker. Thus, the thermal decomposition of OH- and CO32- in the Ni0.1MgAl-MHT sample occurred earlier and faster than that of other LDHs. Therefore, although Ni0.1MgAl-MHT contains less water molecules, hydroxyls and carbonates than other LDHs, its fire retardance is best in all hydrotalcite because of the combination of addition of nickel cations and the microwave radiation treatment.In order to improve the compatibility of polymer matrix and inorganic hydrotalcite particles, the composite of organic anions with long alkyl chain modified hydrotalcite and polymer have been paid great attention. The aim of the organic modification is to increase the surface hydrophobicity of hydrotalcite, and to enhance the compatibility between hydrotalcite and polymer. Therefore, the preparation of organic modified hydrotalcite with the high-crystallinity and efficient synthesis method is important for the practical application of hydrotalcite in the fire retardant field. The sodium stearate surface modified hydrotalcite containing nickel, magnesium, aluminium and carbonate was rapidly synthesized by the microwave hydrothermal crystallization. The change of interaction mode of interlayer carbonate for hydrotalcite occurred with the nickel content increasing. The surface modifier increased the hydrophobicity of hydrotalcite, and the hydrotalcite has different contact angle value due to the addition of different content nickel cations. The modified hydrotalcite S-Ni0.05MgAl has the largest contact angle value equaling 88°. This value is very close to the EVA of 85°. Therefore, the peak heat release rate (pk-HRR) of composite S-Ni0.05MgAl/EVA has been reduced 67.6%. Its time to ignition (Tign) prolongs 19 s, and fire performance index (FPI) reduced 15 kW/m2s in comparison with the pure EVA. Consequently, S-Ni0.05MgAl/EVA has the highest flame retardant efficiency.The practical application of EVA needs the fire retardant because EVA is of one among very flammable polymer. In general, if the inorganic fire retardant achieves good combustion-preventing effects, it needs a larger addition of inorganic fire retardant. And the consequent mechanical properties of composite have been reduced. The crystallinity and crystalline forms of polymer have a close relationship to the mechanical properties. Moreover, the crystallization occurs under non-isothermal conditions during processing of polymer. Therefore, the effect of the surface modified magnesium, aluminium and nickel, magnesium, aluminium hydrotalcite, and unmodified hydrotalcite on crystallization of EVA were investigated by the non-isothermal crystallization kinetics for the first time. In addition, the relationships between the crystallinity, crystalline forms and the mechanical properties of polymer have been studied. Although the hydrotalcite with 20 wt.% loading inhibits the growth of the crystal nucleus, hydrotalcite provides a large quantity heterogeneous crystal nucleus for EVA. Overall, the total crystallization rate was increased due to the less formation time of the crystal nucleus. The results indicate that the hydrotalcite effectively improves the crystallization of composite.It is well known that the rare earth has fine physical features of light, electric and magnet. Therefore, the rare earth and other materials are doped together to constitute a variety of and a lot of new materials. The most prominent feature of the rare earth elements is that a small quantity rare earth will significantly improve the performance and quality of products. It is the first time that the smallest amount of La, Ce, Nd and Y were added into the sodium stearate surface modified hydrotalcite. Furthermore, the different rare earth element leads to the change of physical chemistry properties of hydrotalcite and the effect hydrotalcite with different rare earth on the performance of EVA were contrastively studied. Blue shift or red shift of IR absorbing peak of hydrotalcite was observed due to adding small quantity rare earth. The hydrotalcite with rare earth lanthanum and cerium has better adsorption property for the sodium stearate. In addition, the different rare earth elements have different effects on the contact angle of hydrotalcite. The contact angle value of hydrotalcite containing lanthanum is equal to 87°. This value is very close to that of the EVA. Therefore, the hydrotalcite containing lanthanum shows not only the best compatibility but also the homogeneous and good dispersal in EVA matrix. Consequently, the hydrotalcite containing lanthanum has the best improvement for the thermal properties, fire retardance and mechanical property of EVA copolymer.The purpose of organic intercalated modification is to use the organic anion with a large volume increasing the layer space of hydrotalcite. Consequently, the polymer molecular chains or chain segments intercalated into the layer space of hydrotalcite or winded on the layer, thereby improving the polymer phase compatibility with the inorganic phase. The sodium stearates intercalated modified hydrotalcite with nickel and aluminum were contrastively prepared by the microwave crystallization and the traditional hydrothermal aging. Furthermore, the effects of the crystallization time and N2 protection on the changes of the interior microstructure, the surface properties and the thermal properties of intercalated modified hydrotalcite were explored. At the same time, the differences of effects of intercalated modified and unmodified hydrotalcite containing nickel and aluminum on the properties of EVA were discussed in detail. The contact angle of sodium stearate intercalated modified hydrotalcite Ni3.0Al-MHTN30mis is equal to 99°, and the contact angle of unmodified hydrotalcite Ni3.0Al-CO3 is equal to 46°. It shows that Ni3.0Al-MHTN30m and EVA matrix have the better compatibility because the surface hydrophobicity of intercalated modified hydrotalcite is closer to EVA. Therefore, the intercalated modified hydrotalcites containing nickel and aluminum shows the best fire resistance and mechanical properties.