Preparation Of Manganese-based Layered Double Hydroxides UV Shielding Material And Its Application In Polypropylene

China has abundant salt lake resources,which are rich in salt components such as Na,K,Mg and Li.At present,the development of salt lakes is mainly based on the extraction of potassium and lithium resources.In the process,a large amount of by-products such as magnesium compounds are produced,which not only causes waste of resources,but also causes environmental problems.Therefore,it is necessary to effectively utilize the magnesium resources of the salt lake to promote the comprehensive utilization and balanced mining of the salt lake resources.At present,the development and utilization of magnesium resources in salt lakes are mostly in the primary or low-value stage,and higher-level development should focus on the multi-channel utilization of magnesium-based products.Layered double hydroxides?LDHs?,as a class of high-valued inorganic supramolecular structural functional materials,have been widely used in many fields,especially as UV-shielding materials have shown good effects in high polymer applications.However,the UV-shielding properties of MgAl-LDHs are weak.In order to improve the UV-shielding properties of Mg-based LDHs,it is necessary to study the structure-activity relationship,and further explore its application in the field of UV aging of polymer materials.In view of the current UV aging of polymer and the problems of UV-shielding LDHs,this thesis systematically studied the relationship of the layer composition,the primary particle size and the UV-shielding properties of Mg-based LDHs.On the basis of this,Mg-based LDHs UV-shielding materials were prepared by using high Mg/Li brine as raw materials.The UV-shielding Mg-based LDHs with high added value was obtained while reducing the ratio of magnesium to lithium halide.The preparation process was strengthened by a method involving separate nucleation and aging steps?SNAS?in order to obtain LDHs with uniform particle size.The structure,morphology and particle size of magnesium-based LDHs were investigated by the ratio of feed ratio,reaction temperature and reaction time in the synthesis process.The study provides the basic process parameters for the high value utilization of Mg resources and the separation of Mg and Li.Finally,a series of excellent UV-shielding Mg-based LDHs were further added to polypropylene?PP?for UV accelerated aging experiments,and their anti-ultraviolet aging effects on polymer materials were investigated.The main research contents and results are as follows:1.Preparation of Mg-based LDHs with Different Laminates and Their UV-shielding PropertiesFirstly,M^IIMgAl-LDHs?M=Mg,Co,Ni,Cu,Zn?with the same particle size and different lamellar composition were synthesized by SANS.The experimental results show that ZnMgAl-LDHs exhibit the highest UV-shielding performance in the UVA and UVB regions,and CuMgAl-LDHs exhibit the highest shielding performance in the UVC region.After adding M^IIMgAl-LDHs to PP for UV accelerated aging test,the results show that PP/ZnMgAl-LDHs exhibits the best light aging resistance.This part of the work provides a theoretical basis and technical support for the industrial application and promotion of UV-shielding Mg-based LDHs.2.Preparation of Mg-based LDH with Different Particle Sizes and Their UV-shielding PropertiesUsing different precipitants,nucleation crystallization separation method and hydrothermal synthesis method were used to synthesize and synthesize Mg₂Al-LDHs with different particle sizes and the same lamellar chemical composition.The average primary particle diameters were 63 nm⁴.5?m,respectively.The experimental results show that the optimal primary particle size of Mg₂Al-LDHs for UV shielding is 136nm²70 nm.This part of the work has certain reference significance for controlling the particle size range of Mg-based LDHs for UV shielding.3.Preparation of Mg-based LDHs from Brine and Study on Its UV-shielding PropertiesThe UV-shielding Mg-based LDHs was prepared by SNAS using the brine of East Taijinar salt lake.The process parameters such as raw material concentration,reaction temperature and crystallization time were investigated.It was found that when the brine is diluted to a magnesium ion concentration of 0.8 mol·L^-1,the reaction temperature is 120°C,and the crystallization time is 24 h,a high crystallinity,regular morphology,Mg₂Al-LDHs and ZnMgAl-LDHs can be prepared,and the ratio of Mg/Li in the recyclable liquid obtained by the reaction is reduced to less than 0.85.This part of the work provides the basic process parameters for the development of high-value UV-shielding Mg-based LDHs for salt lake magnesium resources,and provides a new idea for reducing the magnesium-lithium ratio of high Mg/Li salt lake brine.