Thermal and Rheological\nBehavior of the Organogelators\n12-Hydroxystearic Acid and Its Calcium Salt

12-Hydroxystearic\nacid (12-HSA) is widely used as a low-molar-mass\norganogelator (LMOG), especially in the field of lubricants. This\nstudy aims to compare the effectiveness of a technical grade of 12-HSA\nand its calcium salt (12-HSCa) as a gelling agent for different commercial\noils. Their partial or full melting is required for the crystallization\ninto fibers to occur upon cooling. The organogels were mainly investigated\nusing rheological and DSC measurements. In agreement with the literature,\nlow concentrations (<2 wt %) of pure or technical grade 12-HSA\nallowed us to obtain strong organogels with negligible thixotropic\nbehavior. The oil gelation process is very simple and robust and is\nachieved by heating the oil above the melting temperature of 12-HSA\nto complete dissolution and then cooling to ambient temperature. 12-HSCa\nwas less efficient as an organogelator than its fatty acid, requiring\nmuch higher concentrations (>15 wt %) to obtain organogels. Moreover,\nit exhibited a peculiar behavior requiring a very specific temperature\ncycle for gel preparation. This was explained by the polymorphism\nof 12-HSCa, leading to different dissolution–precipitation\nand growth kinetics. The impact of the addition of common surfactants\nin lubricant formulations and the nature of the oils were studied.\nThis information is particularly relevant to the manufacture of greases\nand lubricants. Both LMOGs effectiveness decreased in the presence\nof a surfactant or by increasing the degree of oil refinement due\nto a lower content of polar heteroaromatic components.