is optimally designed for film formation within EV transmission oils has also been evaluated.
Maximising efficiency and biobased content in esters The properties of biobased esters having a viscosity similar to typical base fluids (group III, PAO 4) are shown in Table 1.
Conclusion
Using esters can greatly benefit the intrinsic and extrinsic properties of a lubricant. For the intrinsic properties the choice of raw materials (petrochemical vs biobased), the way they are processed and the way they are transported will influence the product carbon footprint of a molecule. Even if a material is 100% biobased it does not mean that it will be the most sustainable option over the lifetime of an oil as it must also perform in use. When evaluating a lubricant for an application, the intrinsic and extrinsic properties must both be considered to make the most sustainable choice.
Table 1: Neat base oils for evaluation.
A simple way to evaluate base fluid traction coefficient is by measuring them using a Mini Traction Machine (MTM), the test conditions for which are shown in Table 2.
Esters shown in this paper demonstrate that it is possible to improve EV transmission fluid efficiency through de- signing molecules that deliver significant reduction of traction.
Table 2: MTM Test Conditions.
Figure 1 shows the traction coefficient curves for these tests. The solid line shows the traction coefficient curve at 100°C, and the dotted line shows the traction coefficient curve at 40°C.
The first thing to notice is that the traction values at 40°C (dotted line) are higher than their corresponding lines at 100°C (Solid lines), this is because of viscosity and the general trend that the lower the viscosity, the lower the traction. At 40°C there is a large difference between the base oil types. Group III has the highest traction, next are Ester 1 and PAO. Ester 1 is a predominantly petrochemical based ester and has some branching which can give it higher traction. Esters 2 and 3 have a higher biobased content and were designed to have lower traction. This occurs at both 40°C and 100°C. Esters 4 and 5 are de- signed to have maximum efficiency and lowest possible traction as shown in Figure 1. There are two approaches to achieving this. The first is to use petrochemical derived raw materials which have a higher PCF value but have the lowest possible traction and Ester 5 which uses biobased raw materials but still has very low traction.
Figure 1: Traction coefficients by MTM at 40 and 100°C.
References [1] United Nations. The Sustainable Development Goals Report, 2022.
[2] United Nations Climate Change UNFCCC. The Paris Agreement – Publication 2018
[3] Carbon Chain ,2023. Scope 1, 2 and 3 emissions. Available at
https://www.carbonchain.com/ carbon-ac- counting/scope-1-2-3-emissions/
[4] C. Cherel-Bonnemaison, G. Erlandsson, B. Ibach & P. Spiller. Buying into a more sustainable value chain. Mckinsey & Company, 2021. Available online at
https://www.mckinsey.com/ capabilities/operations/our- insights/buying- into-a-more-sustainable-value-chain
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LUBE MAGAZINE NO.181 JUNE 2024
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