Mercedes-Benz A-Class engine cover in bio-based polyamide from DSM. (Photo: DSM Engineering Plastics) Click to enlarge.

The engine cover, used on turbocharged gasoline-engine versions of the new A-Class, has to meet demanding performance specifications, which are complicated by its large size. With dimensions of 575 by 550mm, and operating in an environment that can reach temperatures more than 200 °C, resistance to warpage and high dimensional stability are important.

In addition, the engine cover is required to resist high dynamic loads deriving from engine vibrations, and it needs to be light. Mercedes-Benz’s target was to develop the new A-Class with better fuel-efficiency than the previous generation; overall consumption has been improved by 26%. On top of this, the beauty cover is the most visible component in the engine compartment, so when the customer opens the hood, surface finish is paramount.

EcoPaXX Q-HGM24 has very good heat resistance, demonstrated by a deflection temperature under 1.8 MPa load (DTUL) of 200°C. The cover, which weighs just 1.32 kg (2.91 lbs), can survive continuous-use temperatures of 200 °C, with short term peeks of 235 °C. The compound, which contains glass fiber and mineral particulate reinforcement, produces a better surface appearance than any other polyamide currently used for this type of application, DSM says.

This is the first time that EcoPaXX Q-HGM24 has been used for high volume mass-production, and according to Kees Tintel, EcoPaXX business manager at DSM, more will follow.

Mercedes-Benz states in the Life Cycle Environmental Certificate for the A-Class that production of an engine cover in bio-based polyamide results in only around 40% of the quantity of carbon dioxide emissions that would be necessary in order to produce the same component from a conventional polyamide. The difference per component is around 6.5kg of carbon dioxide emissions.

BBP Kunststoffwerk Marbach Baier GmbH is the supplier for the engine cover. BBP build the production tooling including optimization and process fine tuning which is needed to reach the requested dimensional and surface requirements of Mercedes-Benz.

Since the launch of EcoPaXX, DSM has developed a full portfolio of polyamide 410 grades tuned to the needs of the automotive and other specialty industries.