| Lubricant is one of the most important petro-chemical products and has been widely used in the industry and civil sectors. Howerver, the traditional mineral oil-based lubricant has great hazard on the environment. Many countries have established laws and regulations to confine the use of the lubricant which can not meet the requirement of biodegradability in the areas sensitive to environment. In the meantime, the petroleum resource is decreasing. In order to alleviate the energy stress and protect the environment, the development of a new biodegradable lubricant replacing the mineral oil has important social and economic significance.Di(2-ethylhexyl)sebacate was prepared by the esterification of sebacate acid, the cracking product of castor oil. The synthesis conditions of di(2-ethylhexyl)sebacate were studied systematically, and the physical and chemical properties of castor oil and di(2-ethylhexyl)sebacate were tested. Tribological property and oxidation stability of the lubricant were investigated by four-ball friction and oxidation tube method, the responsibility and compatibility of various additives in the biodegradable base oil were investigated and selected carefully, and the effect mechanism were also discussed. These studies were expected to provide some basis for rational development of the biodegradable lubricants.12-Phosphotungstics acid(PW12) supported on SiO2 were prepared by the sol-gel method, and were first used as catalyst in the synthesis of di(2-ethylhexyl)sebacate. The optimum synthesis processing using PW12/SiO2 as catalyst was following : 1/2.5 of sebacic acid/ iso-butanol, 4 wt% of PW / SiO2, 135℃of the reaction temperature ,5 h of the reaction time. It gave 81.7% of yield.The physical and chemical properties of mixed base oil of d(i2-ethylhexyl)sebacate and castor oil were analyzed. In the case of 60/40 (w/w) of di(2-ethylhexyl)sebacate/castor oil, the 40℃and 100℃kinematical viscosity were 34.99 mm2/s and 5.99 mm2/s, respectively. It also gave 121 of the viscosity index, -41℃of the pour point and 217℃of the flash point. The base oil obtained was appropriate. Moreover, the viscosity of base oil was improved by adding viscosity index modifier and the quality of there of base oil was achieved the standard. The oxidation stability is a leading factor limiting to the popularization and application of the biodegradable vegetable oil-based lubricant. The effect of antioxidant (T202 and T501) on the oxidation stability had been studied. The results showed that the oxidation stability of castor oil was bad because of the double bond, and the oxidation stability of the mixed oil was improved by the addition of T501.The responsibilities of the antifriction additive (T305 and T306) and their compounds in the mixed oil had been investigated. It was found that both of them could improve the load-carrying capacity and antifriction ability. when was added , the PB was 588N and the WSD was 0.305mm in the case of T306 as antifriction additive; the corresponding values were 490N and 0.32mm for T305.The effect of the compounding additives was better than that of single additive. At the level of 1% T306 and 0.5% T305, the antifriction effect was the best, and it gave 784 N of the PB and 0.35mm of WSD. Especially, the antifriction ability under long-time friction was better than that under short-time.
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