High-Pressure Thermophysical Properties of Eight Paraffinic, Naphthenic, Polyalphaolefin and Ester Base Oils

• Published in: Lubricants Vol. 11; no. 2; p. 55
• Main Authors: Villamayor, Antía, Guimarey, María J. G., Mariño, Fátima, Liñeira del Río, José M., Urquiola, Francisco, Urchegui, Raquel, Comuñas, María J. P., Fernández, Josefa
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-01-2023
• Subjects: Analysis; Atmospheric pressure; Compressibility; Contact angle; Contact pressure; Density; Equations of state; Falling bodies; high pressure; Hydraulics; isothermal compressibility; Kinematics; Lubricants; Lubricants & lubrication; Lubricants industry; Lubrication and lubricants; Mineral oils; Petroleum products; Pressure effects; synthetic oils; Temperature; Temperature dependence; Thermal expansion; thermal expansion coefficient; Thermal properties; Thermophysical properties; Vegetable oils; Viscometers; Viscosity; Wetting; Austria
• ISSN: 2075-4442; 2075-4442
• DOI: 10.3390/lubricants11020055

In this work, the thermophysical properties of four mineral (paraffinic and naphthenic) and four synthetic (polyalphaolefin and ester) base oils are measured. Knowledge of these properties is of vital importance for the correct and optimal formulation and design of lubricants, and for the development of equations of state and transport models that adequately represent their properties. Density, isothermal compressibility, thermal expansion coefficient, dynamic viscosity, pressure–viscosity coefficient, and contact angle were determined. To carry out this work, a pρT apparatus, a rotational viscometer, a falling body viscometer, and a contact angle analyzer were used. Highest densities were found for the polyalphaolefin and ester synthetic oils, increasing around 5% from 0.1 to 100 MPa for all the base oils. The density of the synthetic oils is less dependent on temperature changes. For the expansivity and compressibility of all the base oils, decreases with pressure of up to 35% and 45% were observed. From the contact angle measurements, it was observed that base oils with a higher viscosity grade have a worse wetting. The greatest effect of pressure on the dynamic viscosity was obtained for the naphthenic mineral oil and the lowest effect for the polyalphaolefin oil. Paraffinic and naphthenic oils present the highest universal pressure–viscosity coefficients.