Dispersion stability analysis of vegetable oil-based ionanolubricants

Recently, environmentally acceptable lubricants (EALs) developed from vegetable oils are more widely used in the field of lubrication technology as an alternative to mineral and synthetic oils. The homogeneous and long-term stability of additives in base lubricants is a crucial requirement for potential applications of vegetable oil-based ionanolubricants (INLs). In this study, the INLs have been formulated with two vegetable oils, rice bran oil and sesame oil containing TiO2 nanoparticles (NPs) and two ionic liquids IL1, 1-ethyl 3-methylimidazolium dicyanamide [EMIM][DCN] and IL2, trihexyltetradecylphosphonium bis(24,4-trimethylpentyl) phosphinate ([P66614][BTMPP]) with surfactants. The main objective is to find the suitable surfactant among sodium dodecyl sulfate (SDS), Tween 20 (T-20), and Triton X-100 (TX-100) and its optimum additives to surfactant ratio. Dispersion stability of INLs has been investigated by using visual monitoring and dynamic light scattering. The analysis showed that additives start agglomeration and make larger clusters on the 10th and 20th days of formulation, respectively. On the 30th day of formulation, the larger clusters settle down in the bottom due to gravity. However, in spite of this pattern, the additives remain stable in vegetable oils at particular optimum additives to surfactant ratio. Four stable samples were recorded on the basis of dispersion stability analysis. Rice bran oil and IL1-based INLs having additives to TX-100 of 1:2 have found long-term stability. Additives to SDS ratios of 1:6 was found optimum for rice bran oil and IL2-based INLs. Similarly, for sesame oil-based INLs, the additives to T-20 ratios of 1:4 and 1:2 are found optimum for IL1 and IL2, respectively.