Study on the interface and morphological control mechanism of a calcium sulfonate grease thickener

Abstract In this study, lauric acid was introduced during the growth of a thickener of calcium sulfonate grease, and the low-temperature fluidity and drop point of the grease were greatly improved by regulating the morphology of the thickener and the oil-fixing ability of the surface. The aspect ratio of the thickener was increased from 1 to 5, and the specific surface area was increased by 40.12%. Similarly, at low temperatures, the viscosity decreased by 11.63%, and the drop point increased by nearly 100 °C. A comparison of the effects of lauric acid, amines, and alcohols with different polar end groups on the surface adsorbability and wettability of the thickener revealed that the adsorption qualities of the three molecules were similar, but only lauric acid and amines significantly improved the lipophilicity of the surface of the thickener and increased the drop point of the grease by nearly 100 °C. Through molecular dynamics simulation, the alkyl chains of linear acid and amine molecules adsorbed on the surface of the thickener are found to be almost perpendicular to the surface of the thickener, which makes the interface base oil difficult to slip, increases the adsorbed oil content and the effective radius of the thickener, and effectively increases the drop point of the grease. The long alkyl chain of the linear-chain alcohol molecules is almost parallel to the surface of the thickener, which has little effect on the physicochemical properties of the grease.