| Bittern and red mud are two kinds of by-products, with a great amount of production in industry. The improper disposals of them will waste resources, and even cause environmental and safety risks. In this paper, bittern was used as raw material to prepare three kinds of LDHs with coprecipitation method after introducing different trivalent metal ions. On this basis, bittern and red mud are used as raw materials to prepare LDHs with the introduction of red mud instead of trivalent metal ions. After that, the structures, thermal properties and morphologies of four kinds of LDHs are tested using XRD, TGA and SEM methods. Then four kinds of EVA/LDHs composites were prepared to study the flame retardant properties, smoke suppression performance and thermal stability properties by methods of LOI, CCTS, SDT, TG-IR. Also the flame retardant mechanism were generally analysed. Several research outcomes are shown in the following:1. Mg/Al-LDHs was synthesized based on bittern successfully, and XRD, TGA and SEM showed that Mg/Al-LDHs had a complete structure, high moisture content and the appearance looks good. Mg/Al-LDHs were applied to EVA to prepare EVA/Mg/Al-LDHs composites. After a series of tests, it was shown that the flame retardant properties of EVA/Mg/Al-LDHs composites were much better than that of pure EVA. The LOI(EVA3 highest of 29.8%) and PHRR(EVA3 lowest of 222.65 kW/m2) values were much better. And the smoke suppression performance and thermal stability performance were improved significantly.2. Mg/Fe-LDHs was synthesized based on bittern successfully, and XRD and SEM showed that Mg/Fe-LDHs had complete structure and good appearance in a certain range of concentration. Mg/Fe-LDHs can obviously improve the flame retardant properties, smoke suppression performance and thermal stability on EVA. And EVA4 has the higest LOI value of 27.3%, but EVA2 has the lowest PHRR value of 278.14 kW/m2. However, the flame retardant effect is not as well as Mg/Al-LDHs.3. Mg/Al/Fe-LDHs was synthesized based on bittern successfully, and XRD and SEM showed that the structure and appearance of Mg/Al/Fe-LDHs is not as good as Mg/Al-LDHs and Mg/Fe-LDHs. And the flame retardant properties and smoke suppression performance of Mg/Al/Fe-LDHs are between the above two kinds of LDHs. Among these, EVA3 has the highest LOI value of 25.3% and lowest PHRR value of 287.21 kW/m2.4. Mg/Al/Fe-HTLcs was synthesized based on bittern and red mud successfully, and XRD, TGA and SEM tests showed that Mg/Al/Fe-HTLcs have the general structure of the hydrotalcite. Its flame retardant properties, smoke suppression and thermal stability on EVA were significantly improve. And the highest LOI value is 28.3%(EVA3) and the lowest PHRR value is 204.59 kW/m2(EVA2). Compared with the LDHs unused red mud, Mg/Al/Fe-HTLcs based on bittern and red mud showed better flame retardant performance.5. It is workable way that prepare LDHs using bittern and red mud as raw and apply it on EVA as flame retardant. It can achieve the overall utilization of both two resources, which is a brand new safety thought to dispose red mud and bittern. At the same time, the LDHs prepared in this experiment have wide utilization potential. It also throws a sprat for the development of new type flame retardants. |
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