People generally associate lubricants with oils but in fact there are a great many applications where non-liquid lubricants are used, with the most obvious of these being greases.
According to the ASTM (American Society for Testing and Materials), lubricating grease is a solid or semi-fluid substance containing a thickener agent and a lubricating liquid. Other ingredients such as additives and solid lubricants can also be added to give it specific properties. This definition establishes the fundamental concept that grease is not a very viscose oil but rather a thickened oil, a multi-phase system made up of two distinct components represented by a thickener agent and fluid oil. Therefore, the consistency of the product can be varied by varying the amount of thickener, something which is codified by an NLGI number (National Lubricating Grease Institute - USA). The properties of grease are therefore linked to the nature and type of thickener and lubricant it contains.
Thickeners can be soap (calcium, lithium, sodium and such like), complex soap (calcium, lithium, lithium-calcium, aluminium and so forth), bentone or polyurea based, while the oils dissolved inside the thickener can be mineral, semi-synthetic or synthetic based.
As far as production is concerned, greases are much more complex than oils. Manufacturing greases is not simply a case of mixing the individual components together, but requires a rather complex production process involving chemical reactions produced by the different components.
Greases are used for lubricating and protecting mechanical machinery as an alternative to liquid lubricants, particularly when a lack of space or problems connected with dripping make it difficult to use oil. Grease is sometimes applied continuously (in the iron and steel industry), while other times it is used to lubricate a component for its working life (rolling bearings or small reducers).
Choosing the correct product is highly complex and is best taken with the help of expert technical advice, since there are many factors that can influence the way products function and effect machinery lubricated with grease.
Eni is one of the main producers of greases and has a wide range of products that can satisfy the needs of both the industrial and automotive sectors.