Effect of TiO2 and SiO2 nanoparticles on traction, wear, and high-shear viscosity of PAG lubricants under elastohydrodynamic (EHL) conditions for refrigeration systems

Mohd Zaki, Sharif and Ismail, Mohd. Farid and Ngatiman, Nor Azazi and Abdollah, Mohd Fadzli bin and Abd Aziz, Mohd Syafiq and Mohamad Redhwan, Abdul Aziz and Ramadhan, Anwar Ilmar (2026) Effect of TiO2 and SiO2 nanoparticles on traction, wear, and high-shear viscosity of PAG lubricants under elastohydrodynamic (EHL) conditions for refrigeration systems. Lubricants, 14 (2). pp. 1-22. ISSN 2075-4442

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Official URL: https://www.mdpi.com/2075-4442/14/2/78

Abstract

This study tests TiO2 and SiO2 nanolubricants in PAG oil using a Mini Traction Machine and an Ultra Shear Viscometer. The loads were 20 N and 40 N. The entrainment speeds ranged from 2.5 to 500 mm/s. The slide-to-roll ratio (SRR) ranged from 25 to 150%. The nanoparticle concentrations were 0.01, 0.03, and 0.05%. The ball size was 19.05 mm, and the disc was 46 mm. All tests were run at 40 ◦C. Only the 0.05% concentration lowered traction compared with PAG at a fixed SRR. TiO2 at 0.05% showed the largest drop, up to 4.89% at 20 N and 2.99% at 40 N. However, lower concentrations increased traction. All the nanolubricants reduced wear. TiO2 at 0.03% gave the lowest wear, with a reduction of about 35 µm at 40 N. Nanolubricant samples stayed between 40.2 and 40.5 ◦C, while PAG reached about 41.0 ◦C. TiO2 produced slightly lower temperatures than SiO2. Ultra-shear tests from 40 to 100 ◦C showed shear thinning. In most conditions, TiO2 at 0.05% kept the highest viscosity at 40 and 60 ◦C, up to 12% above PAG. SiO2 showed smaller changes. TiO2 delivered better friction, wear, temperature, and viscosity performance. Overall, both nanolubricants at 0.03% are suitable when wear reduction and thermal stability are prioritised over traction reduction, such as in refrigeration applications, while the 0.05% suits high-load or high-shear use.

Item Type:	Article
Uncontrolled Keywords:	TiO2/PAG nanolubricant, SiO2/PAG nanolubricant, Elastohydrodynamic lubrication (EHL), Mini traction machine (MTM), Ultra shear viscometer (USV)
Divisions:	Faculty Of Mechanical Technology And Engineering
Depositing User:	Sabariah Ismail
Date Deposited:	13 Jul 2026 06:55
Last Modified:	13 Jul 2026 06:55
URI:	http://eprints.utem.edu.my/id/eprint/29964
Statistic Details:	View Download Statistic

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