Polyol Esters in Lubricant Oils : lubricity, seal swell performance and oil's solubility

Used as lubricant oil and base oil, polyol esters have different functions.

Owing to the adsorption of the polar ester groups onto metal surfaces to form a lubricating film, polyol esters can effectively reduce friction and wear, improving equipment lubricity. Polyol esters can also improve the swellability of rubber seals to avoid excessive deformation.

Polyol esters have good solubility in additives and oxidation products, which can prevent precipitation and deposition, and ensure the long-term stability of the oil performance.

 

The classification of polyol esters

Based on the number of hydroxyl groups in the polyol, polyol esters are mainly ciassified into neopentyl glycol esters (difunctional), trimethylolpropane esters (trifunctional), and pentaerythritol esters (tetrafunctional), and the latter 2 are the most widely used.

According to the type of fatty acid, it can be divided into saturated fatty acid esters and unsaturated fatty acid esters. Industrial esters are often use mixed fatty acids through esterification to balance comprehensive performance.

The comparison among different base oils

 

The core advantages of polyol esters

Thermal stability: the thermal decomposition temperature of polyol ester is usually 50 ℃ higher than that of di-esters, which can keep the molecular structure complete under high temperature for long time and delay the oil deterioration.

Wide temperature-range application: synthetic polyol esters have excellent high-temperature stability and good low-temperature liquidity, working over a wide temperature range of 40 to 200, meeting the full range of operational requirements, from cold-start capabilities to continuous operation in high-temperature environments.

Excellent viscosity-temperature characteristic: polyol esters have a high viscosity index, meaning their viscosity changes little with temperature. It can keep the oil film strength under high temperature and the viscosity won't too high at low temperatures to provide stable lubricant protection for equipment under different temperatures.

Low evaporation loss: Polyol esters possess high relative molecular masses and strong intermolecular forces; consequently, their evaporative loss is significantly lower than that of mineral oils of comparable viscosity, which helps extend oil change intervals and reduce the consumption of make-up oil.

Biodegradability: Polyol esters possess good biodegradability; they can be rapidly broken down by microorganisms in the natural environment, and their negative impact on the ecosystem is far lower than that of mineral oils.

 

The main functions of polyol esters in lubricant oils:

Polyol esters in lubricant oil mainly has 3 different functions.

As the base oil

Used as the lubricant base oil, polyol esters can form an independent lubrication system. In the areas like aviation engine oil, precision instrument oil that has a strict demand for oils' performance, polyol esters base oil are the first choice.

 

Besides, polyol esters can be formulated with PAO or mineral oils. Although PAO has an excellent low temperature performance and viscosity temperature characteristic, it has a low solubility to polar additives. The addition of polyol ester complements it, combining the two allows for complementary performance, balancing low-temperature startability, high-temperature stability, and formulation compatibility.

 

Used as a lubricant additive:

Even used a small proportion in other base oils, polyol ester has prominent performance.

Improve lubricity: the polar groups of polyol esters can adsorb on the metal surface to form a boundary lubricant film to improve the comprehensive anti-wear performance.

Enhance additive solubility: the polar groups of polyol esters increase the polarity of the formulation, ensuring that polar additives-such as antioxidants and extreme-pressure agents-dissolve fully and disperse stably, thereby preventing precipitation or loss of effectiveness.

Improve seal swell characteristics: While PAOs and mineral oils tend to cause rubber seals to shrink, the moderate swelling effect of polyol esters counteracts this, maintaining seal volume and elasticity to prevent oil leakage.

Reduce volatility and improve energy efficiency: The low volatility of polyol esters can reduce oil loss at high temperatures. Their excellent lubricity reduces mechanical friction losses, to improve energy efficiency.

 

Role in Boundary Lubrication

Boundary lubrication protection: Under boundary lubrication conditions-such as low-speed, high-load operations or frequent start-stop cycles-the polar groups of polyol esters form a shear-resistant protective adsorbed film on metal surfaces. This effectively inhibits abrasive and adhesive wear, extending the service life of friction pairs.

 

Chorus-professional polyol esters application solutions

Chorus is a professional lubricant additive supplier in China, we can provide you with excellent performance polyol esters, including TMP ester 3970. Chorus TMP ester 3970 is a saturated polyol ester that is widely used as a synthetic base stock and a lube additive in a wide range of applications like air compressor oils, gear oils, and metal working fluids, with high thermal stability and oxidation stability.

The polyol ester TMP3970 effectively can inhibit the formation of sludge and varnish, extend the oxidation, and prolong equipment service life. Additionally, its high solubility allows it to effectively counteract the solubility limitations of PAO when formulated together, ensuring the overall stability of the lubricant.

 

We can also provide you with other types of synthetic base oils, such as di-ester, POE synthetic lubricant base oil, trimellitate, trimethylolpropane trioleate (TMPTO) ester oil, PAO base oil.

 

We can provide you with professional polyol ester solutions.

Contact us for more detailed information.