| The synthesis method of new inorganic thermal stabilizers and flame retardants—Ca/Mg/Al hydrotalcite-type like compounds were studied. And synthesis conditions,structure and properties of Ca/Mg/Al hydrotalcite-type like compounds have been investigated in this thesis.Under suitable conditions,various products of Mg-Al-hydrotalcite were synthesized by coprecipitation method.According to the identity of the composition in the layers,the possibility of Ca2+-doped with Mg-Al-hydrotalcite was explored for the first time.A series of carbonate pillared Ca-Mg-Al or Ca-Al hydrotalcite-type like compounds have been prepared by substituting Mg2+with Ca2+partly or entirely in the layers. The products were characterized by XRD and FT-IR.XRD certified that the samples all had hydrotalcite structure,nice crystal forms and high purity.The analysis of IR proved that CO32-was intercalated between the double layers of hydrotalcite-structure.They both showed that the synthesis of hydrotalcites was successful.Based on a lot of experiments,the influence of the experiment factors to the structure and the property of hydrotalcite were discussed, such as the different sorts of the material,temperature,pH value,Mg/Al ratio,stirring rate and volume flow etc..Various products can be prepared through controlling the reaction conditions.Applications of Ca/Mg/Al hydrotalcite-type like compounds as flame retardants and thermal stabilizers in the PVC materials have also been investigated.The results showed that Ca/Mg/Al hydrotalcite-type like compounds can improve the heat stability of PVC.Both the flame retardant and smoke suppressed properties of MgAl-CO3-LDHs were clearly superior to those of magnesium hydroxide and aluminium hydroxide.With the same additive quantity(20Phr),Ca-Mg-Al hydrotalcite-type like compounds had superior properties of the flame retardant and smoke suppressed,which proved that partial substitution of Ca2+into the layers significantly enhanced flame retardant and smoke suppressed properties. |
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