Synthesis of Calcium Lanthanum Hydrotalcite and Its Effect on Thermal Stability of PVC
Calcium-lanthanum hydrotalcites(Ca-La-LDHs)were prepared by hydrothermal method.The effect of different cation ratios,hydrothermal time and hydrothermal temperature on the synthesis and their thermal sta-bility of Ca-La-LDHs were studied.The best synthesis conditions were obtained:n(Ca2+)∶n(La3+)=3∶1,170 ℃ of hydrothermal temperature,8 h of hydrothermal time.The products were characterized by FTIR,thermal anal-ysis,scanning electron microscopy and XRD analysis.The effect of rare earth hydrotalcite on the thermal stabili-ty and plasticization performance of PVC was studied through the Congo red experiment,high temperature aging experiment,torque rheology experiment,tensile experiment and electrical conductivity experiment.The results show that under the optimal preparation conditions,Ca-La-LDHs thermal stabilizers can significantly improve the thermal stability of PVC,and the static thermal stability time is 87 min.The Ca-La-LDHs sample reduces the equilibrium torque,increases the dynamic thermal stability time,and significantly delays the release rate of HCl from PVC,thereby improving the dynamic thermal stability.Ca-La-LDHs improved the tensile strength and elongation at break of PVC sheets.The Ca-La-LDHs thermal stabilizer hinders the cleavage of C-Cl and C-H bonds in PVC,which inhibits the generation of HCl and C=C bonds,then reducing the further catalysis of PVC degradation by HCl.
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