Abstract
Objectives: To study the viscosity index for oil used as biodegradable lubricant using tree methods. Methods: Viscosity index for oil used as biodegradable lubricant (coconut oil, soybean oil, corn oil, rapeseed oil) was determined using a set of Schott Ubbelohde-type viscometers selected according to the values of their constants, so that the margins of the uncertainty, inherent in the Hagebach–Couette correction, does not exceed the error allowed for the measurements. The measurements were carried out at 40 ± 0.1 and 100 ± 0.1 °C, according to the recommendation of ASTM D2270. Findings: The viscosity index of soybean oil is the highest and the viscosity index of rapeseed oil is the lowest. The viscosity index determined with the calculator for coconut oil is one unit higher than that obtained by the formula (1). The viscosity index of corn oil determined with relation (1) is 151, and the one determined by computer is 25 units higher. The viscosity index of rapeseed determined with relation (1) is 143, and the one determined with the computer program is 23 units higher. The viscosity index determined for soybean oil determined using the program has a negative value. The viscosity oils used as biodegradable lubricant were determined using tree methods: ASTM D 2270 and method graphically using ASTM D 341. Viscosity index calculation was performed with a computer program using kinematic viscosity at 40 °C and 100 °C. The viscosity-temperature coefficient for oils used as biodegradable lubricant can vary by a factor of 10 depending on the temperature. The viscosity of oil oils used as biodegradable lubricant is dependent upon temperature. Viscosity decreases as temperature increases because the molecules vibrate more, and interact less. Application: The three methods for determining the viscosity index can be applied both to vegetable oils used as biodegradable lubricants and to oils of SAE class. The term biodegradable lubricant includes a wide range of lubricants, such as: vegetable oils; hydrogenated vegetable oils; vegetable oils with high oleic acid content; synthetic esters produced from vegetable oils. Keywords: Viscosity Index, Viscosity-Temperature Coefficient.
Highlights
The value obtained for the viscosity index of oils coconut, oil soybean, oil corn, and oil rapessed in Table 1, together with their kinematics viscosities at 40 and 100 °C and viscosity-temperature coefficient
The viscosity index determined with the calculator for coconut oil is one unit higher than that obtained by the formula (1)
The viscosity index of corn oil determined with relation (1) is 151, and the one determined by computer is 25 units higher
Summary
The main characteristics of environmentally friendly lubricants, called biodegradable lubricants are as follows: they conserve energy; longer operating time: less waste; low consumption: less throwing; they are recyclable; they are biodegradable; have low ecotoxicity; have low pollution risk for water, soil, and air. Advantages and disadvantages of biodegradable lubricants: lower air, water, and soil pollution; minimal risks to health and safety; easier destruction due to their biodegradability. VI of the biodegradable lubricants is calculated from the kinematic viscosities at 40 oC of the three oils, the reference and the one whose index must be determined, using – according to ASTM D 2270-93 [1] – the relation: VI = L L −U −H ×100 (1). The relation is used to determine the viscosity indices of the oils with values less than or equal to 100, for which the value of U is between L and H
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