MOLYKOTE® G-5025 Boosts Performance Efficiencies in New Brake System
Case study: Rubber and plastic-compatible grease met endurance-testing needs across a wide temperature range, with as low as -40°C.
With the global push toward the adoption of electric vehicles (EVs), automotive OEMs are looking for ways to adapt their technology for complete vehicle electrification, including the braking system. Electro-hydraulic braking (EHB) – a stepping stone to fully electromechanical brake-by-wire systems of the future – replaces vacuum booster brake technology. Expected to grow by 30% market share by 2025(1), EHB systems work in a vacuum-free environment, which is a benefit in EV applications.
The Application
A global brake system manufacturer headquartered in China began developing its wire control brake system (WCBS) – a new one-box EHB system. The system, which is combined with a backup electronic parking brake as a failsafe, has the benefit of being smaller and lighter – with fewer parts than traditional booster brakes and two-box EHB systems –and can be used in both new EVs and traditional combustion engine vehicles.
The manufacturer was looking for a reliable lubricant that offered rubber and plastic compatibility and would meet system endurance tests under a wide service temperature range.
The Challenge
Initially, a competitor’s polyalkylene glycol (PAG) lubricant had been selected for the application, but it wasn’t able to meet the challenging requirements to provide sufficient performance.
The competitor’s lubricant worked well in temperatures as low as -30°C, but the brake system showed reduced output pressure when compared to the lubricant’s room temperature performance. According to the client, energy loss in lithium-ion batteries is a significant concern, especially in the winter.
Electro-hydraulic braking (EHB) is a fast-growing technology that replaces older booster brake technology. The braking unit, as shown here, is controlled by electronic actuators that activate the brake hydraulics.
The Solution
The MOLYKOTE® Specialty Lubricants team collaborated with the EHB system project manager to understand the project’s technical requirements and recommend a solution. The lubricant would need to endure millions of load cycles under service temperatures that ranged from -40°C to +120°C. MOLYKOTE® lab testing showed that one particular lubricant – MOLYKOTE® G-5025 Grease – was compatible with various rubber/elastomer substrates (e.g., EPDM) and plastics, so the team believed it would deliver the reliable protection the application required.
Lab comparisons performed in the DuPont lab showed that MOLYKOTE® G-5025 Grease could deliver much lower torque than the competitor’s product at extremely low temperatures and encouraged the manufacturer to try it in a road test. When put to the test, the MOLYKOTE® grease reduced the pressure gap, which met the manufacturer’s expectations.
The EHB system’s output pressure was more stable across temperature changes with MOLYKOTE® G-5025 Grease than it had been with the competitor’s product. The grease helped the brake unit operate safely and reduced energy consumption – especially in low temperatures – by reducing starting and running torque as demonstrated in the table below. After a clear demonstration of the operating effectiveness of the MOLYKOTE® Specialty Lubricant, MOLYKOTE® G-5025 Grease was specified successfully.
| Low temperature (-40°C) | Competitor’s grease | MOLYKOTE® G-5025 Grease |
| Starting torque | 891.3 mN.m | 110 mN.m |
| Running torque, 20 min | 169.8 mN.m | 23.2 mN.m |
Reliable Plastic-Compatible Lubrication & Low-Temperature Performance
MOLYKOTE® G-5025 Grease was developed for the lubrication of over-running clutches in starter motors, but it has been shown to be a high-performance lubricant across wide temperature ranges – not just in starter motors, but in other automotive applications with demanding durability requirements. It shows good anti-wear properties and offers resistance to oxidation and moisture that can lead to extended component life.
In addition to the specific customer application featured in this case study, MOLYKOTE® G-5025 Grease also has now been specified for similar applications by other key market players.
Typical Properties of MOLYKOTE® G-5025
Specification writers: These values are not intended for use in preparing specifications. Please contact your local MOLYKOTE® sales representative prior to writing specifications on this product.
| Standard* | Test | Result |
| Colour | Yellow | |
| DIN 51818 | NLGI class | 44228 |
| DIN ISO 2137 | Worked penetration | 295-325 mm/10 |
| IP 396-02 | Dropping point | 248°C |
| CTM 0033A | Bleed (150°C, 24 hr) | 0,0268 |
| CTM 0033A | Evaporation (150°C, 24 hr) | 0,0362 |
| DIN 51805 | Flow pressure @ -40°C | < 500 mbar |
| DIN 51802 | Emcor (7 d, distilled water) | 0 |
| DIN 51 350 pt.5 DIN 51 350 pt.4 |
Four-ball-tester: Wear scar (1,000 N, 60 sec) Weld load |
1.0 mm 4,400 N |
| Service temperature range | -40°C to +180°C | |
| *DIN: Deutsche Industrie Norm. ISO: International Standardisation Organisation. IP: Institute of Petroleum. CTM: Corporate Test Method; copies of CTMs are available on request. | ||
Source: MOLYKOTE® G-5025 Grease for automotive applications paper
