Imagine a new deck of cards on the poker table. However, when the finished oil, the base oil with these polymers, is heated up to operating temperature, the polymers uncoil and stretch out so that they interact with the layers of oil that are moving relative to two metal surfaces creating more resistance to flow, which we know as viscosity. When cold, and coiled up tight, these polymers do not significantly affect the viscosity of the base oil in which they are dissolved. Polymers are high molecular weight, or long, viscous molecules that coil up tightly when cold and stretch out, or uncoil, when heated. Let’s look at what these polymers are and how they work to understand shear’s influence on them. These polymers are not only affected by temperature but also by shear. Viscosity index (VI) modified oils contain polymers to lower the change in viscosity with respect to temperature, which is quantified by the VI as we discussed in the March 2023 TLT. Understanding these characteristics is critical for OEMs to meet higher and higher fuel economy requirements and for you to make sure you choose the right oil to protect your engine from premature wear. Two more characteristics to understand about viscosity under fundamentals of lubrication are high temperature high shear (HTHS) and permanent shear stability index (PSSI).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |