Ester Polarity

The key element that differentiates the value of Ester base stocks begins with the polarity of the Ester molecule. This polarity affects the way Esters behave as lubricants in the following ways:

Volatility<
The polarity of the ester molecules causes them to be attracted to one another and this intermolecular attraction requires more energy (heat) for the esters to transfer from a liquid to a gaseous state. Therefore, at a given molecular weight or viscosity, the esters will exhibit a lower vapor pressure which translates into a higher flash point and a lower rate of evaporation for the lubricant.

Lubricity<
Polarity also causes the ester molecules to be attracted to positively charged metal surfaces. As a result, the molecules tend to line up on the metal surface creating a film which requires additional energy (load) to penetrate. The result is a stronger film which translates into higher lubricity and lower energy consumption in lubricant applications.

Detergency
The polar nature of esters also makes them good solvents and dispersants. This allows the esters to solubilize or disperse oil degradation by-products (varnish and sludge) which might otherwise be deposited as varnish or sludge, and translates into cleaner operation and improved additive solubility in the final lubricant. Simply put Esters leave little to no deposits, but can remove deposits formed by other lubricants or fluids.

Biodegradable
While stable against oxidative and thermal breakdown, the ester linkage provides a vulnerable site for microbes to begin their work of biodegrading the ester molecule. This translates into very high biodegradability rates for ester lubricants when compared with traditional mineral base stocks.