Study On Preparation,modification And PVC Thermal Stability Of HTLCs Based On Fly Ash Extraction And Salt Lake Mg-rich Brine

Hydrotalcite compounds(HTLCs)are a new type of high-efficiency PVC heat stabilizer,which has the advantages of greenness and low cost,and has always been favored.In this paper,high-concentration fly ash leaching solution and salt lake magnesium-rich brine are used as raw materials to prepare MgAl binary hydrotalcite,and industrial wastewater waste liquid is used as a metal ion source to prepare metal ternary hydrotalcite to achieve low-cost and green products.With the aid of FT-IR,XRD,SEM and TG analysis,the effects of various conditions on the structure of hydrotalcite and the thermal stability of PVC materials are studied.The main research contents and results are as follows:(1)Using fly ash extract and salt lake magnesium-rich brine as raw materials,MgAl binary hydrotalcite was prepared by co-precipitation-hydrothermal method,and the aging time,aging temperature,n(Mg²⁺)/n(Al³⁺)were systematically studied,n(CO₃^2-)/n(Al³⁺)and other factors,determine the best preparation conditions:aging time is 6 h,aging temperature is 140?,n(Mg²⁺)/n(Al³⁺)is 2:1,n(CO₃^2-)/n(Al³⁺)is 1:1,fly ash leaching droplet acceleration is 0.3 m L·min^-1,salt lake magnesium-rich brine droplet acceleration is 0.6 m L·min^-1,reaction stirring temperature is 60?,The concentration of Na OH is 2 mol·L^-1.The prepared MgAl binary hydrotalcite has high crystallinity,significant layer structure and good thermal stability.This research lays a certain theoretical foundation for the high-value utilization of fly ash leaching liquid and salt lake old brine waste.(2)On the basis of the preparation of binary hydrotalcite,ZnMgAl ternary hydrotalcite is prepared with electrogalvanizing waste liquid as zinc source,CaMgAl ternary hydrotalcite is prepared with calcium chloride wastewater as calcium source,and acidic Cu Cl₂ etching waste liquid is used to prepare CaMgAl ternary hydrotalcite.Cu MgAl ternary hydrotalcite was prepared for the copper source.The effects of different types of hydrotalcite on the thermal stability of PVC were studied.Research shows that when n(X²⁺)/n(Mg²⁺)=1:2(X=Zn,Ca and Cu),the obtained hydrotalcite has better regularity and crystallinity.Ternary hydrotalcite can significantly improve the thermal stability and mechanical properties of PVC materials.CaMgAl ternary hydrotalcite has the best effect and can increase the heat resistance time of PVC at 180?to 140 min.(3)In order to improve the compatibility and dispersibility of hydrotalcite in PVC materials,two different surface modification coupling agents,3-aminopropyltriethoxysilane(A110)and n-octyltriethoxysilane(N308)Organic surface modification of hydrotalcite.Research shows that the hydrotalcite after wet surface modification improves the dispersibility of hydrotalcite in PVC material and the interface compatibility with PVC,thereby improving the mechanics of PVC material Performance and thermal stability.