High heat resistant polyamides and polyesters for under the hood applications

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DSM recently introduced the world’s first plastic air intake manifold (AIM) with integrated charge air cooler (CAC) made of high temperature resistant Stanyl polyamide 46. Reason enough to talk to Mr. Joost d’Hooghe, Segment Sales Manager Automotive Europe of DSM, to learn more about high heat resistant polyamide grades for under the hood applications, and a high performance polyester that challenges established engineering plastics in high precision parts.

PA46 – the material that withstands peaks up to 250°C

The world’s first high-heat plastic air intake manifold with integrated charge air cooler goes now in series production at a German OEM. Here high temperatures and high internal pressures are major challenges. To cool down the air stream, the engine developer made use of one of the latest developments in turbo charging systems: a liquid cooled charge air cooler (CAC) which is integrated into the air intake manifold and delivers higher efficiency than an equivalent air-to-air cooler.

air intake manifold

Air Intake Manifold made of Stanyl polyamide 46 (source: DSM)

Integrating the CAC into the AIM reduces the air duct length, improves engine responsiveness and delivers higher performance while still meeting the latest gas emission requirements. However, integrating the cooler into the AIM drives the internal air temperature up to 220°C in continuous use, with peaks up to 250°C. This increase in pressure and temperature puts additional demands on the manifold material. Stanyl Diablo OCD2100, a 40% glass fiber reinforced polyamide 46, is able to meet these temperature and pressure requirements.

The finished part, featuring a weight reduction of about 40% versus aluminum, is assembled from several moldings using hot gas welding (other welding technologies such as vibration welding can also be used). Even with a 40% glass fiber reinforcement and higher melting point, the material can be processed on standard machines, and the same moulds as for other polyamide grades can be used.

PA6 – the material oil sumps are made of

Oil sumps offer great potential for weight reduction. But they do also present a special challenge: their exposed position under the engine means that they have to withstand considerable mechanical stress caused by, for example, stones flying up from the road, and impacts from curb stones if the vehicle is driven off the road onto the pavement.

The French Tier One supplier Steep Plastique has developed a special design fot the oil sump for the new 2.0 liter diesel engine of PSA that is 60% lighter than the previous used metal version and that withstands the high impact requirements of this application. The grade used for the oil sump is Akulon K224-HG7, a 35% glass reinforced, heat stabilized polyamide 6 with the necessary oil resistance.

Oil Sump (source: DSM)

Oil sumps made of polyamide 6 offer great potential for weight reduction (source: DSM)

Another Tier One supplier, German BBP, has developed an oil sump for Mercedes-Benz which is around 50% lighter than the metal version it replaces using the AkulonUltraflow K-FHG7 grade. In order to guarantee the performance of the part, the two companies subjected it to some very demanding application tests, including vibration, stone impact, and an engine drop test.

Biobased Materials – the alternative for temperatures up to 200°C

A thermoplastic crankshaft cover can be considered as a masterpiece of engineering design: Fiber orientation, the number and position of gating points, and the design and integration of the various inserts have all to be considered in order to minimize warpage and ensure tight seals between the cover and the engine block and oil sump. The cover also has to resist tightening of bolts fixing it to the engine block and the sump (each of which is built to different tolerances).

Crankshaft cover DSM

Crankshaft cover made of biobased polyamide (source: DSM)

The company KACO has developed such a multi-functional crankshaft cover in bio-based polyamide 410 for the latest generation of diesel engines of the Volkswagen Group. It will be used on Volkswagen’s new MDB modular diesel engine platform, implemented across its Audi, Seat, Škoda and VW brands. Weight has been reduced significantly as the EcoPaXX grade is 45% less dense than aluminum. Compared to covers made from aluminum, system costs for the thermoplastic cover are considerably lower, partly due to the use of an integrated, fully automated and highly energy-efficient production cell. The production cell does not only mould the crankshaft cover, but also integrates two separate seals: the first, in PTFE, is placed into the mould by a robot, and EcoPaXX is over-moulded onto it; the second, in LSR, is then moulded directly into the part using a 2K process. This results in reduced energy consumption during production, as well as zero material waste: “The part comes out of the injection moulding cell ready to be assembled onto the engine block. No trimming is necessary at all” says Andreas Genesius, head of project management at KACO. EcoPaXX polyamide 410 is 70% derived from renewable resources, and the polymer is certified 100% carbon neutral from cradle to gate.

Other examples made of EcoPaXX are sensor housings or the engine cover of the Mercedes B class where the material has to withstand continuous temperatures of up to 200°C. The good thermo stability and very good chemical resistance makes this biobased polyamide a good alternative for a wide range of applications under the hood.

PET – The material for dimension-critical automotive parts

Temperature and humidity as a challenge: Electronic components in vehicles do operate under a wide range of temperature and humidity conditions. Therefore, there is a need for materials to retain key properties such as strength, stiffness and impact strength under demanding hot-humid conditions. About one year ago, DSM launched Arnite A-X07455, a 50% glass reinforced PET (polyethylene terephthalate) engineering plastic which is highly resistant to hydrolysis.

Injection moulded parts from conventional PET lose as much as half of their tensile strength after 1,000 hours at 85°C and 85% relative humidity. Parts made from the Arnite A PET keep around 90% of their initial strength under the same conditions. This was proven in simulated conditions in DSM laboratories. And due to its very good dimensional stability it can be used for a variety of automotive under the hood applications where temperatures are around 150-170°C, including throttle valve bodies, sensors, air control valve housings, electronic throttle control (ETC), exhaust gas recirculation (EGR) covers, and ignition systems. With a tensile stress at break of 200MPa (according to ISO 527), the material enables substitution of metals or higher cost engineering plastics such as polyphthalamides (PPA) and polyphenylenesulphide (PPS) in automotive parts that require high dimensional accuracy.

(based on an interview with Joost d’Hooghe, DSM Segment Sales Manager Automotive Europe on 14.08.2014, Main picture: Joost d’Hooghe)

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