The Study On Synthesis Of Mg-Al-LDHs For Heat Stabilizers Of PVC

The anionic layered material LDHs has the metal cation two-dimensional plate which can be controlled, the interlayer region containing charge compensating anions and exchangeable anions.Due to the special structure, chemical composition and exchangeable interlayer anions that are between adjacent LDHs layers, LDHs can replace the toxic heat stabilizer and become the new heat stabilizers which are non-toxic, inexpensive and efficient for PVC.This study examines the impact of synthetic raw materials, synthetic method, synthetic temperature, the ratio of raw material and crystallization conditions on the structure and composition of the synthesized products in detail. Firstly, according to the different magnesium source and aluminum source, different Mg/Al and different hydrothermal temperature, Carbonate hydrotalcite precursors are prepared using co precipitation-hydrothermal method, and the synthetic products are tested and analyzed, studying the effect and influence of different experimental conditions on product function. According to the experimental results, the appropriate magnesium and aluminum sources, Mg/Al and the hydrothermal temperature were determined, and then MgAl-CO3-LDHs with high purity,good dispersion, morphology rules were prepared by the new-style equipment which can intensify the mass transfer process. Excellent properties of MgAl-CO3-LDHs materials prepared by two methods were compared.The conventional co precipitation-hydrothermal method utilizes Mg(NO3)2·6H2O、Al(NO3)3·9H2O and MgCl2·6H2O、NaAlO2 as the magnesium source and aluminum source, and Na2CO3、NaOH used as precipitation agent, the Mg/Al was 1.5,2,2.5,3, hydrothermal temperature is 140℃、160℃、180℃ and 200℃.Analysis of the experimental results determined the optimal synthesis condition:magnesium and aluminum sources were Mg(NO3)2·6H2O、Al(NO3)3·9H2O, the precipitation agent was Na2CO3、NaOH, Mg/Al=2.0, hydrothermal temperature was 160℃.In the experiment that rotor-stator reactor was used prepared MgAl-CO3-LDHs,under the best synthesis conditions which have been obtained, research for the effect on the reaction product about the speed of rotor-stator reactor, cycle time of product in the reactor and the feeding flow rate were done to optimize the synthesis conditions further. The speed of rotor-stator reactor were 500r/min,1000r/min,1500r/min,2000r/min and 2800r/min, cycle time of product in the reactor were 0.5h,1h and 1.5h, the feeding flow rate were 100ml/min,200ml/min,300ml/min and 400ml/min. Through experimental characterization and analysis finds the best synthesis condition:The speed of rotor-stator reactor was 2800r/min, cycle time of product in the reactor was 1.5h, the feeding flow rate was 300ml/min.Further experiment is that synthetized LDHs was used as functional additives and added to the polyvinyl chloride (PVC) for preparing LDHs/PVC composite material, and test thermal stability of LDHs/PVC composite material. The results showed that LDHs prepared by the conventional co precipitation-hydrothermal method was added to the PVC material and only increased the initial coloring of PVC, and did not prolong the thermal stability time.LDHs prepared by rotor-stator reactor was added to the PVC material, increased the initial coloring of PVC and prolong the thermal stability time.