Polyamides are being widely used in the automotive industry as a base material for under-the-hood applications, such as engine covers, inlet manifolds, radiator end-caps, oil-pans, etc. Main polyamides employed are polyamide 6 and 66. These polymers are being made from monomers such as caprolactam, adipic acid and hexamethylene diamine. All of these materials are derived from crude oil, and do have significant carbon footprints. In order to decrease the influence on climate change and global warming, there is a lot of interest in bio-based materials with reduced or zero carbon footprint, which at the same time can bring the high performance needed for the under-the-hood application.
Mercedes-Benz has chosen a high performance polyamide largely made from renewable resources for the engine beauty cover of the Mercedes-Benz A-Class cars. Around 70% of the raw materials used to make the polyamide 410 in DSM’s EcoPaXX® Q-HGM24 reinforced compound are derived from the beans of the castor plant (Ricinus communis).
The engine cover, used on turbo-powered petrol-engine versions of the A-Class, has to meet very 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 warping 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 A-Class with better fuel-efficiency than the previous generation, and in fact, overall consumption has been improved by 26 percent. 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 beauty cover, which weighs just 1.320kg, 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.
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.
DSM launched EcoPaXX in 2009 in answer to increasing market demand for high performance durable bio-based engineering plastics.
In the Mercedes-Benz Life Cycle Environmental Certificate for the A-Class it states that the production of an engine cover in bio-based polyamide results in only around 40% of the quantity of carbon dioxide emissions that would be otherwise necessary in order to produce the same component from a conventional polyamide. The difference per component is around 6.5kg of carbon dioxide emissions indicating that this technology can make a significant contribution towards climate protection.”
Implementation and benefits
Although EcoPaXX is 70% bio-based, it is performs as well if not better than conventional materials used for engine covers. It combines mechanical properties with excellent chemical resistance and has the highest melting point of any bio-based aliphatic polyamide, making it very suitable for applications needing high heat resistance, such as engine covers for turbo engines and crank shaft covers.
The fact that it can be used in so-called beauty covers in cars made by a company like Mercedes-Benz, which puts so much emphasis on the perfect combination of form and function, speaks volumes for the surface finish of the product.
BBP Kunststoffwerk Marbach Baier GmbH is the supplier for the engine cover. BBP built the production tooling line including optimizing and fine tuning the processes which are 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.
Mercedes-Benz concludes in its Life Cycle Environmental Certificate:
“The Mercedes-Benz A-Class not only meets the highest standards in terms of safety, comfort, agility and design, but also satisfies all current requirements with regard to environmental compatibility. This environmental certificate documents the major progress which has been achieved in comparison to the preceding model of the A-Class.
Moreover, a higher proportion of high quality secondary raw materials and components made from renewable raw materials is used. In all, the 2012 model year A-Class has a significantly improved Life Cycle Assessment compared to its predecessor model.”
Bio-based EcoPaXX is a material which is very suitable for demanding automotive (under-the-hood) applications. Next to the Mercedes A-class engine cover, EcoPaXX is also being used for BMW and Bentley engine covers. VW uses the material for a crankshaft cover in their Golf models, which is an even higher demanding application.
Castor oil and its derivative sebacic acid are readily available raw materials, and DSM has ample capacity for further increase of production. Many projects are in the pipeline and are expected to be commercialized in the coming years.
Regulations on the use of biobased plastics in cars would further help to grow EcoPaXX and other biobased plastics in automotive applications. This will lead to further reduction in carbon dioxide emissions during the production phase of the used plastics and thus will help to fight climate change.
DSM feels that there is high potential for the use of this bio-based material in many applications in the future.”
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“EcoPaXX is 70% bio-based, but its “green” credentials come at no cost to performance,” says DSM’s
Tintel. “It combines superb mechanical properties with excellent chemical resistance in various media. It also has the highest melting point of any bio-based aliphatic polyamide, making it very suitable for applications needing high heat resistance, such as engine covers for turbo engines and crank shaft covers.The fact that it can be used in so-called beauty covers in cars made by a company like Mercedes-Benz, which puts so much emphasis on the perfect marriage of form and function, speaks volumes for the surface finish it makes possible.”