The application

Bethel Automotive Safety Systems, Co., Ltd., 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 lubricant solution 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.

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 manufacturer, energy loss in lithium-ion batteries is a significant concern, especially in the winter.

The solution

The MOLYKOTE® Specialty Lubricants team collaborated with Bethel’s 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 the extreme 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.