Reseach On The Layer Cations And Interlayer Guests Regulation Of LDHs And Its Impact On The Thermal Stability Of PVC

Layered double hydroxides (LDHs) are a kind of efficient non-toxic heat stabilizer with supramolecular layer structure. Thus, the research of new type LDHs on the structure assembly, thermal stability properties and mechanism has important theoretical value and practical significance.This paper makes full use of regulation property between layer cations and interlayer guests of LDHs, and prepared three kinds of supramolecular structures PVC heat stabilizer, which were Mg2-xCaxAl-NO3-LDHs, MgCaAl-CO3-LDHs and MgAl-Glu-LDH by the methods of nucleation-crystallization separation and ion exchange.The resulting LDHs were analyzed by powder X-ray diffraction (XRD), infrared spectroscopy (FT-IR), differential scanning calorimetry (TG-DTA), inductive coupled plasma (ICP), CO2-temperature programmed desorption (CO2-TPD) and thermogravimetry. The results showed that the structure of Mg2-xCaxAl-NO3-LDHs and thermal stability of PVC dopped Mg2-xCaxAl-NO3-LDHs changed with different doping amount of calcium; The "single drop-ion exchange method" can be obtained to prepare high purity MgCaAl-CO3-LDHs, whose thermal stability has been improved compared with before; LDHs intercalated with glutamic acid had good early suppression shading performance, and improved the aging pigmentation of PVC, this may be related to the supramolecular effect between layer cations and interlayer guests.In order to develop into the reason of calcium base hydrotalcite exhibiting excellent early thermal stability, in this paper, the effect of stabilizers on the thermal stability of PVC was studied through the deployment of composite heat stabilizer formula, and the properties of MgCaAl-CO3-LDHs and MgAl-CO3-LDHs adsorbed ZnCl2 were studied. The results indicated that zinc soap in composite heat stabilizer is the main reason for maintaining PVC early performance; Calcium base hydrotalcite can not only effectively absorb HCl produced PVC degradation, and participate in process of calcium soap well eliminating the role of ZnCl2, which hindered the happen of "zinc burn" phenomenon, thus maintaining the better early performance of composite heat stabilizer.In addition, on the basis of predecessors’ research in our laboratory, this paper adopted a new method to verify the changes of structure and particle size in the process of MgAl-CO3-LDHs effecting the thermal stability of PVC, and discussed the function mechanism of MgCaAl-NO3-LDHs on the thermal stability of PVC according to the similar research ideas and methods. Finally, this paper put forward a new experimental method for visual simulation and the dynamic characterization of function process between LDHs and PVC, consequently abtained thermal stability mechanism of LDHs on PVC at different aging stages.