Synthesis And Lubricating Property Study Of Thiadiazole Schiff Base Derivatives

Lubricating oil is used in various mechanical transmission and hydraulic equipments toreduce or control the friction and wear between two contact surfaces,and it is a kind of lubricating material which can maintain the performance of the machine and prolong the working life of the friction pair.Lubricating oil is composed of base oil and additives,and its performance has a close relation with additives.It has been found that the active sulfur and nitrogen,respectively,is a kind of extreme-pressure,anti-wear and friction-reducing elements,which play a very important role in extreme pressure,anti-wear and friction-reducing performance of the lubricating oil.In addition,in the process of friction,nitrogen helps to form adsorption protective film on metal surface,and to relieve corrosive wear of metals caused by excess sulfur.As a kind of nitrogen heterocyclic compounds,1,3,4-thiadiazole compounds contain relatively high nitrogen and sulfur content in the molecular structure.In addition,this kind of compounds do not contain phosphorus and metal elements,no damage to the environment,is a kind of environmental protection multifunctional green lubricating oil additive with wide application prospect.In this paper,five series of 1,3,4-thiadiazole Schiff base derivatives which have not been reported in the literature were synthesized,including total thirty-four compounds.The synthetic compounds were characterized by UV,IR,and 1H NMR to determine its molecular structure.The corrosion inhibiting performance in liquid paraffin base oil of these compounds were studied.The thermal stability of six novel compounds A4,A6,A12,B9,B11,C2 were investigated,and the anti-wear,friction-reducing and extreme-pressure performances of compounds A2,A4,A6,A12,B2,B9,B11,C2,C3,D,E1,E2,E3 in 150 SN and liquid paraffin base oil were evaluated.Thermogravimetric analysis showed that the thermal decomposition temperature of the six kinds of compounds(A4,A6,A12,B9,B11,C2)is all above 250 ?,indicating the determination of compounds have good thermal stability,which can be satisfied with the thermal stability requirements of the lubricating oil additives used for the internal combustion engine oil,gear oil and hydraulic oil.The copper strip corrosion test of additives showed that after respectively adding different mass fraction of compounds in the base oil(liquid paraffin),the copper corrosion level had reduced to 1a or 1b from 1b or 3a by blank base oil,indicating the determination of compounds have favorable corrosion resistant performance.The testresults of the friction-reducing and extreme pressure properties in 150 SN base oil show that the decreased degree of the friction coefficient of sample between 30~50% after adding different kinds of additives in the base oil,and the increased degree of extreme pressure values between 40~150%.Compared with the base oil,the effect of friction-reducing and extreme pressure of the sample containing additives increased significantly.The test results of friction-reducing and anti-wear performance based on the liquid paraffin oil show that the friction coefficient and wear volume all shows the tendency of decreased first and then increased after adding different mass fraction of additives in base oil,and reach the minimum value in 0.5 wt%,the effect of friction-reducing and anti-wear is best.The reduced degree of the friction coefficient between 40~50%,the decrease of the wear volume level between85~95%,reflecting the determination of compounds possess satisfactory friction-reducing and anti-wear properties.The SEM-EDX and XPS were used to observe the surface morphology and analyze chemical composition of the surface,the results of SEM showed that the spot size and the corrosion of the grinding surface lubricated by adding the additives were obviously lower than that of the base oil.The combination of EDX and XPS test results suggest that additives adsorbed and reacted with metal surface,the adsorbed and chemical adsorption film made up of nitrogenous substances and chemical reaction film containing Fe2O3,Fe3O4 and iron sulfide was formed in the process of friction.The tribological mechanism of synthetic compounds as the lubricating oil additive was explored.