ExxonMobil Chemical Company
SpectraSyn Elite™ mPAO Extends Synthetic Basestock Performance Range

By Sandra Mazzo-Skalski, Performance Product Specialist, ExxonMobil Chemical | TLT CMF Plus November 2010

 

ExxonMobil Chemical continues to expand its portfolio of synthetic fluids and lubricant basestocks to meet the increasingly stringent requirements of the industrial and automotive markets. The latest addition to the company’s polyalphaolefin (PAO) synthetic basestocks is SpectraSyn Elite™ metallocene PAO (mPAO) 150 cSt.

SpectraSyn Elite™ mPAO basestock joins one of the industry’s broadest portfolios of synthetic basestock viscosity grades, which includes the SpectraSyn™ family of low- and high-viscosity PAO and Synesstic™ Alkylated Naphthalene (AN) basestocks.

The expansion of the company’s synthetics portfolio reflects tougher requirements for today’s lubricants, including:

• superior performance under more severe operating conditions
• contributions to greater energy efficiency
• maintaining performance over longer drain intervals
• operating at lower oil volumes

SpectraSyn Elite™ mPAO basestock introduces the advantages of metallocene catalyst technology, enabling customers to improve upon conventional PAO lubricants by providing even greater shear stability and viscosity index. These advantages are coupled with the low-temperature properties of PAOs.

While metallocene catalysts are new to the SpectraSyn™ product line, ExxonMobil Chemical has more than two decades of experience and expertise in bringing new, metallocene-based products to market.

Molecular Structure
Conventional PAOs of high viscosity possess a prominent backbone with side chains randomly arranged on either side (Figure 1). SpectraSyn Elite™ mPAO basestock is manufactured to a viscosity of 150 cSt using a proprietary metallocene catalyst. This catalyst produces a uniform, comb-like structure similar to that of conventional PAOs but without short side chains.


Figure 1.

Shear Stability
Shear stability is an important property for both automotive and industrial oils, as it indicates an oil’s ability to retain viscosity in service. A lubricant that retains its viscosity under high shear conditions will more efficiently protect operating equipment for a longer period. This can mean direct savings in operating costs for the customer.

Figure 2 shows clearly the minimal shear loss incurred by SpectraSyn Elite™ mPAO basestock. After 20 hours at 100°C, even very high viscosity mPAO shows a loss of less than 4% in the KRL shear test (CEC L-45-A-99).


Figure 2.

This is confirmed by comparing the shear loss that was experienced by two 75W-90 automotive gear oils. One was formulated with SpectraSyn Elite™ mPAO basestock, while the other was formulated with non-metallocene 150 cSt PAO. The SpectraSyn Elite™-based gear oil suffers less than half the shear loss of the non-metallocene-based gear oil after 60 hours under the KRL shear test (Figure 3).


Figure 3.

Viscosity Index
A fluid with a higher viscosity index (VI) is less sensitive to temperature and can be used in applications requiring a greater operating range. Figure 4 shows the viscosity index of several common fluids. SpectraSyn Elite™ mPAO basestock has a 100 VI unit advantage over poly-isobutylene (PIB) and a 40 VI unit advantage over conventional PAO of comparable viscosity.


Figure 4.

This higher viscosity index enables formulators to develop lubricants that provide better protection at higher temperatures and improved fluidity at lower temperatures. These characteristics may reduce energy losses during operation.

Generally for fluids of similar structure, the higher the viscosity, the higher its viscosity index. So it is not surprising that the VI of SpectraSyn Elite™ 150 cSt mPAO basestock would be greater than that of a conventional 100 cSt PAO. What is surprising is the magnitude of the difference, more than 30 VI units (Figure 5).


Figure 5.

For formulators trying to produce lubricants with improved efficiency and greater wear protection, Spectra Syn Elite™ mPAO may prove to be the base stock of choice. Two examples of ISO VG 460 gear oils blended with SpectraSyn Elite™ mPAO base stock illustrate the higher viscosity index that can be achieved versus blends of conventional 100 cSt PAO (Figure 6). The 20-unit increase translates into better performance across the entire operating temperature range.


Figure 6.

A similar result is seen when Spectra Syn Elite™ mPAO base stock is used to blend an ISO VG 460 gear oil (Figure 7).


Figure 7.

Low-temperature Properties
SpectraSyn Elite™ mPAO basestock provides improved protection at higher temperatures, but it also allows formulators to blend lubricants with improved fluidity at low temperatures. This may translate into better cold-start capability and the ability to meet increasingly demanding specifications.

Looking again at an ISO VG 460 circulating oil, Figure 8 demonstrates that at 0°F and at -20°F, oil blended with Spectra Syn Elite™ mPAO base stock has a consistently lower Brookfield viscosity than the circulating oil blended with conventional PAO. The advantage of Spectra Syn Elite™ mPAO base stock is especially pronounced at -20°F.


Figure 8.

This superior low-temperature capability is further reflected in its pour point. Figure 9 clearly demonstrates that Spectra Syn Elite™ mPAO base stock has pour points about 20°C lower than poly-isobutylene fluids and about 5°C below conventional PAOs of similar kinematic viscosities. Even at a 50 cSt disadvantage, Spectra Syn Elite™ mPAO base stock still has a 3°C lower pour point than a conventional 100 cSt PAO.


Figure 9.

Summary
SpectraSyn Elite™ metallocene PAO basestock builds on more than two decades of ExxonMobil Chemical’s metallocene catalyst development and represents the latest addition to one of the industry’s broadest portfolios of synthetic basestock viscosity grades, which includes the SpectraSyn™ family of low- and high-viscosity PAO and Synesstic™ Alkylated Naphthalene (AN) basestocks.

SpectraSyn Elite™ metallocene PAO basestock offers formulators the following advantages:

• improved shear stability to meet the requirements of severe applications
• ability to blend lubricants with higher viscosity index
• fluidity at low temperatures while maintaining sufficient viscosity at higher temperatures

Other products in the Exxon Mobil Chemical portfolio include Spectra Syn™, high- and low-viscosity PAOs for thermal and oxidative stability; Spectra Syn Plus™, a low-viscosity PAO offering high thermal and oxidative stability; SpectraSyn Ultra™, offering viscoelastic properties from a high-viscosity PAO; and Synesstic™ Alkylated Naphthalene (AN), a leading blend stock providing stability with excellent additive solubility.

Visit www.spectrasynelite.com for more information.

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