Aluminium stearate (aluminum tristearate) is a white coloured powder, wax-like powder (metallic soap) that dissolves well in vegetable oils upon heating. It is soluble in glycol, alkali, BTX, chlorinated hydrocarbons. If aluminium stearate is in high concentration, gelling can be seen upon cooling. It exhibits the following properties: good gelling and thickening action, excellent water repellence, transparency and a synergistic effect with zinc stearate or calcium stearate. Aluminium stearate exhibits a relatively high solubility in hydrocarbon solvents (such as mineral spirits) when compared to other metallic stearates. It is insoluble in water, alcohol and ether; but when hot, it is readily soluble in benzene, acids and common solvents.
Aluminium stearate is synthesised via the precipitation process using high quality stearic acid. This is done by adding aluminium isopropoxide to stearic acid in anhydrous pyridine, inducing the precipitation of the pyridine complex. Pyridine is then removed under vacuum to give the aluminium stearate.
Aluminium stearate is used as an emulsifier in cosmetics. They are used for their lubricating properties. The stearate salts also increase the thickness of the oil portion of cosmetics and personal care products. Hence, finished cosmetics products are typically not transparent.
Aluminium stearate is used as lubricant in the plastic industry. It is used in the production of polyamides and thermoset plastics.
Aluminium stearate is used as a thickener in Varnishes/Lacquers, an anti-settling agent for pigmentation, as a pigment suspension, and an agent to improve water resistance and gloss. It is useful as a water repellent agent, a hydrophobic agent, and a waterproof agent in the paint industry.
Aluminium stearate is used as lubricant for wire drawing in metal industry and as a de-foaming agent in oil industry. It is also used as a waterproofing agent in the textile industry and as an anti-caking agent in pesticides. Aluminium stearate is used in rubber industry for preventing stickiness.