Silicone Vacuum Grease Explained
Grease is a lubricant in a semi-solid state. It is generally applied to those machinery parts where liquid lubricants would not stay and need to be applied only occasionally.It also works as a sealant to keep out moisture and other unwanted materials from the system.How is grease made?Grease is made with a base oil or lubricant mixed with a thickener. The quality and properties of grease are therefore primarily determined by the following factors-
- The base oil
- The thickener
- Special purpose additives, if any
How is the base oil in grease important?We all know that lubricants can oxidize. But do you know that greases can oxidize too? That is because of the base oil that makes up the grease.Good base oil = Good greaseLow Quality base oil = Low Quality greaseOxidized base oil = Oxidized grease
Hydrocarbon base oil in grease, when oxidized, will produce carbonization leading to progressive hardening and crust formation. This can lead to substantial damage to the moving machine parts as well as permanently ruin the o-rings and seals.What is the Drop Point in grease?Generally, grease breaks down when subjected to temperatures that exceed its melting point or the Drop Point. This is that critical temperature where the gel structure of the grease breaks down and turns into liquid form. The base oil, thickener and the additives separate. This transformation is always irreversible. On cooling, it regains neither its consistency fully nor its former performance. When heated beyond its Drop point, grease softens, leaks and bleeds into the system. For vacuum systems this spells disaster.So does it mean that the Drop Point of a grease is determined by its base oil’s boiling point?Yes, primarily. It also depends to an extent on the proportion and quality of the thickener used. How a particular grease will behave under extreme conditions like high pressure and temperature depends upon the properties of the base lubricant in it.Does the grease have a low temperature too?Yes, just like the melting or Drop point, grease has a low temperature too at which it stiffens. At this cold or low temperature grease becomes too hard to be of any use for the moving components. Instead of lubricating them, hardened grease can damage the o-rings and seals or the moving parts like bearings etc. by stiffening and jamming them.Again, the base oil determines the lowest temperature of grease.
Are all greases alike?No, the difference in the components makes greases differ from one another. There are hydrocarbon greases as well as silicone greases. Then there are synthetic multi-purpose greases. Within these 3 categories too, greases differ based on the type and grade of the base oil used. Different industries require grease that caters to their specific needs. For example, Dielectric grease is used by the electrical industry; special automotive greases are used by the automotive industry;Food grade grease is required in machines where it is likely to come in contact with edible ingredients and so on.As the name suggests, the basic difference lies in the type of base oil in both. Hydrocarbon based greases are mineral oil based while silicone grease has silicone oil as the base oil. Hydrocarbon based grease is used primarily by the automotive industry and mechanisms requiring high frictional lubrication which makes use of grease’s thixotropic property. Silicone grease on the other hand is most suited for lubrication as well as a sealant because of its water resistant property.