Technical Topic: Saturated Synthetic Esters

SATURATED SYNTHETIC ESTER BASIS HYDRAULIC FLUIDS

Synthetic Esters - HEES (Hydraulic Oil Environmental Ester Synthetic)
Due to technical and environmental capability HEES products currently lead in the category of biodegradable hydraulic fluids. Group HEES further splits into 2 sub-categories:

1. Unsaturated / Partially saturated synthetic esters (iodine number >10)Their technical applicability in high demanding applications depends on composition of the mixture.
2. Saturated syntetic esters (iodine number <10) currently provide the most sophisticated, environmentally acceptable solution for hydraulic systems. Technical advantages of saturated esters are performance benefits, extreme stability, wide temperature range, compatibility, high levels of biodegradation and renewable resources.

Like with conventional hydraulic fluids HEES products can vary in quality and technical parameters. The wide variety of hydraulic fluids available under the HEES classification can perform quite differently. This is primarily dependent on ester base composition; unsaturated, saturated or their mixture. When considering which HEES fluid to use it is therefore important to verify ester base oil. HEES based on Saturated esters are the highest performing products.

Whats is the difference betwen Saturated and Unsaturated Esters? Synthetic Esters are formed by a process called esterification (condensing or combining an acid with an alcohol). The saturation of a fluid is based on the chemical bonding within the fluid itself; where bonds can be open or closed. Fewer open bonds means the esters are better protected against oxidizing and ageing.

The easiest way to identify the number of open bonds within a fluid is to compare Iodine number. The higher the Iodine number, the greater the number of bonds that can interact and oxidize. Saturated Esters have an Iodine number < 10.