Research subject: Non-soap-based greases formulated with bentonite are widely considered suitable lubricants for demanding industrial applications due to their high thermal stability and resistance to harsh environmental conditions. However, the inherent structure of natural bentonite can limit its lubrication performance. Acid activation is one of the effective strategies to enhance its functional properties.
Research approach: In this study, Iranian bentonite was activated using sulfuric acid at two concentrations (0.25 M and 3 M) and then incorporated as a thickening agent with SN180 base oil. The synthesized grease samples were evaluated using FTIR, XRF, FESEM, Four-Ball Wear Test (ASTM D2266), and Dropping Point Test (ASTM D2265).
Main results: The FTIR and XRF results indicated that acid activation reduced aluminum and structural water content while increasing the silica content in bentonite. FESEM images confirmed increased porosity and surface heterogeneity as a result of acid treatment. The four-ball wear test showed that the grease containing bentonite activated with 0.25 M acid exhibited superior anti-wear performance compared to other samples, whereas the 3 M acid-treated sample demonstrated weaker performance due to structural degradation. All samples showed acceptable thermal performance in the dropping point test, with values exceeding 272 °C. These findings suggest that the proper control of acid activation conditions plays a crucial role in optimizing the structural and functional properties of non-soap-based greases.