Preparation And Modification Of Hydrotalcite And Its Effect On Thermal Stability Of PVC

Polyvinyl chloride?PVC?due to its own defects,its processing temperature is 180?,and decomposition temperature is 130?.Therefore,in the processing process,it is necessary to add heat stabilizer to prevent its thermal decomposition in the processing process.In view of the problems of high price and poor thermal stability in the production and application of polyvinyl chloride?PVC?heat stabilizer,the preparation and modification of hydrotalcite and its influence on the thermal stability of PVC were studied.The effects of different organic metal salts on the thermal stability of polyvinyl chloride resin were analyzed.Conventional binary hydrotalcite?LDHs?was synthesized.Rare earth ternary hydrotalcite and hydrotalcite were modified by surface modification.The three synthesized hydrotalcites were characterized by Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.The properties of three kinds of hydrotalcite were analyzed and studied.The effects of three hydrotalcites on the properties of polyvinyl chloride?PVC?materials were studied.The effects of processing aids on the properties of polyvinyl chloride?PVC?were studied by thermal gravimetric analysis?TGA?,SEM micro-characterization,Congo red test,static oven aging test and smoke suppression test.The main research contents and results are as follows:?1?The effects of organic metal salts on the thermal stability of polyvinyl chloride?PVC?were tested under the condition that other processing aids were not changed.It was found that the thermal stabilization effect of calcium acetoacetate was better than zinc acetoacetate and aluminium acetoacetate in the same dose of heat stabilizer.?2?Mg-Al-LDHs binary hydrotalcite and rare earth lanthanum-doped ternary hydrotalcite La-LDHs were successfully prepared.The results show that the thermal stability of polyvinyl chloride?PVC?can be effectively improved by adding rare earth elements in hydrotalcite.When the molar ratio of La³⁺to Al³⁺is 1:3,the thermal stability of hydrotalcite in polyvinyl chloride?PVC?is the best.According to Congo red test results,the thermal stabilization time of adding lanthanum to aluminium ratio of 1:3 is 20 minutes longer than that of adding conventional hydrotalcite to PVC.The thermal stability of lanthanum-added hydrotalcite-polyvinyl chloride resin is better than that of conventional hydrotalcite.The smoke density of PVC-LDHs is 79%and that of PVC-LaLDHs is 55%when the lanthanum-aluminium ratio is 1:3.The smoke density of PVC-LaLDHs is reduced by 24%.?3?La-LDHs with a lanthanum-aluminium ratio of 1:3 were surface modified with sodium dodecyl sulfate,sodium polyoxyethylene lauryl ether sulfate,potassium monoalkyl phosphate and polyoxyethylene ester of fatty acid.XRD,FTIR and SEM analysis showed that the original crystalline state of hydrotalcite was destroyed by Modified Hydrotalcite with sodium dodecyl sulfate and sodium polyoxyethylene lauryl ether sulfate,which made the crystalline form of hydrotalcite no longer single.However,potassium monoalkyl phosphate and fatty acid polyoxyethylene ester do not destroy the original structure of hydrotalcite and have good crystallinity.The tensile strength of Modified Hydrotalcite and polyvinyl chloride increased by 80%when the amount of surfactant was only 4%.The compatibility of hydrotalcite and polyethylene was improved by surfactant,the dispersibility and fluidity of hydrotalcite in polyvinyl chloride were improved,and the mechanical properties of polyvinyl chloride were improved.