Thesis (M.Sc.)--Chulalongkorn University, 2009

The lubricants produced from petroleum base stock are generally toxic to environment and difficult to dispose after use. Vegetable oils can be used as an alternative base stock for lubricants besides petroleum base because of their excellent lubricity, biodegradability, viscosity characteristic and low volatility. The hydraulic lubricants from vegetable oil were manipulated in this research. Their physical properties including viscosity, viscosity index, flash point and four- ball wear were investigated comparing with those of commercial hydraulic lubricants. OIL-HR, lubricants produced from rice bran oil was exhibited excellent lubricity and viscosity–temperature properties in the same level as commercial industrial lubricants. The oxidation stability of manipulate hydraulic lubricants from soybean oil and rice bran oil under the tested conditions of oven oxidation test in the presence of 0.5% diphenylamine exhibited excellent antioxidant property. The copper corrosion behavior of hydraulic OIL-HC, OIL- HP, OIL-HSF and OIL-HR, lubricants produced from coconut, palm, sunflower and rice bran oil, revealed these blended oils were classified into 1a class, which showed good anticorrosion. The hydraulic lubricant from rice bran oil displayed good anticorrosion and viscosity-temperature characteristic.