What are disadvantages in using biodegradable lubricants when compared to “normal oils”?

This week we’re looking at the disadvantages in using biodegradable lubricants. Even though there’s a very strong case to made in favor of biodegradable lubricants, they can only come into their own if the disadvantages in using biodegradable oils are fully understood.

What are the common groups of biodegradable oils?

In order to understand where the disadvantages in
using biodegradable lubricants lie, it is necessary to review the various types of biodegradable lubricants to point out their advantages and disadvantages:
Vegetable oils; derived from corn, soybean, rapeseed (canola), sunflower, peanut, olive oil amongst others.

In their natural form the disadvantages in using these as biodegradable lubricants, are their poor thermal, hydrolytic and oxidation stability.

• For example, most natural vegetable oils cannot withstand reservoir temperatures greater than 80ºC.
• In addition, water, even in small amounts of a few hundred parts per million, is the natural enemy of vegetable oils and can cause serious foaming and degradation problems. In general, these oils also exhibit low cold-flow abilities. 
• Another disadvantage of using vegetable oil is the high pour point. This problem is often addressed by the addition of chemical additives (pour point suppressants) and/or blending with other fluids with lower pour points. 

If a high degree of biodegradability is required, then biodegradable synthetic esters are added to improve cold-temperature properties.

On the other hand, if the goal is to maintain the so-called biobased property, where at least 51 percent of the lubricant is made of natural biomaterials, then a portion of the blend could be light mineral oil with low pour points

Synthetic Esters; based on natural and renewable resources or fully synthetic esters based on petrochemical raw materials. These products have good antioxidation characteristics and seal swell properties.

Synthetic Polyalphaolefines (PAO) have excellent low-temperature properties, but tend to shrink rubber seal materials.

Synthetic Polyglycols (PAGs), can be both water soluble (ethylene-oxide) and water insoluble (propylene-oxide).

Water soluble PAGs are ideally suited for fire-resistant lubricants. Although the disadvantages in using these biodegradable lubricants is their tendency to emulsify water in certain equipment, such as gear boxes. This will cause foaming, sludge and corrosion.

Another major disadvantage of both PAOs and PAGs is their poor solubility with regard to additives.

Most of the manufacturers, depending on the application and the environmental performance, are using mixtures of the above base fluids to overcome these notable disadvantages in using biodegradable lubricants.

Esters are predominantly used as base fluids in the formulation of the environmentally acceptable lubricants.

How to overcome the disadvantages in using biodegradable lubricants.

Obviously the best procedure to follow in overcoming any of the disadvantages in using biodegradable lubricants is in the correct selection for the application.

Because of the complex nature of biodegradable lubricants it’s best to seek professional advice. Habot Synthetic Lubricants can offer you advice and a range of products that’ll steer you well away from the disadvantages in using biodegradable lubricants discussed in this article.