04-Jul-16 A new high-temperature resistant grade of its Arnitel thermoplastic copolyester elastomer (TPC) for production of flexible hot charge air ducts used in turbocharged engines has been developed by global materials supplier DSM. Arnitel HT will allow system suppliers to produce the ducts in one material using a single process step. The current standard practice is to assemble separate elements in hard thermoplastics or metal and soft thermosetting rubbers, which need to be produced in diverse operations. DSM says switching to Arnitel HT will provide producers with a significant improvement in process efficiency, cost reductions of up to 50% and weight reduction of up to 40%.
Hot charge air ducts, common features in advanced petrol and diesel engines, need to withstand very high temperatures for long periods. Furthermore, in order to handle movements of the engine relative to the cooler (which is fixed on the chassis of the car) and because they need to be easy to install, flexibility is an important requirement. These needs are normally met by using ducts with a central section in a rigid high temperature thermoplastic, such as Stanyl or Akulon polyamide, and end sections in a thermosetting polyacrylate, ethylene acrylic or fluoro rubber with a woven reinforcement. DSM says there are several disadvantages associated with this approach, the two most important of which are weight and cost. Assemblies based on these thermoset rubbers are heavy because their relatively low mechanical performance dictates the need for thick walls to be able to handle the demands of the hot charge air duct.
In addition, total system costs of rubber-plastics or metal rubber products can be quite high, for various reasons. The production process is a multi-step one: moulding of the various elements, followed by assembly. This adds costs and takes extra time and it also introduces extra opportunities for defects to be introduced, both during production and in use. Since rubber processing and plastics processing require different skills, companies producing the ducts may even buy some sections rather than make them themselves. In addition, to reduce the risk of failure due to creep at the joints in these assemblies, reinforcement rings are placed inside the tubes, another assembly step. DSM believes Arnitel HT eliminates all these disadvantages. With its ability to withstand continuous operating temperatures of up to 180°C and peaks of up to 190°C, it has high temperature resistance. Arnitel HT also has good resistance to the types of oils and chemicals found in automotive engine environments. Critically, Arnitel HT’s combination of elasticity with high mechanical strength means that it can be used to produce the entire duct in a single piece, using 3D suction blow moulding. Wall thicknesses can be approximately halved.
Kurt Maschke, global segment manager Air/Fuel at DSM, says: “Ducts produced in Arnitel HT can withstand the internal operating pressures which are demanded by car producers, not only for models in production today but also for upcoming generations. And by using a single solution based on a material with excellent mechanical performance and a relatively low density in an optimised design, it is possible to obtain weight savings of as much as 40%.” One of the first producers of hot charge air ducts to take advantage of this new material is Cikautxo, a firm headquartered in Spain which produces rubber and plastics components. The company worked with DSM on the development of the first part in Arnitel HT, and exchanged valuable information for improvements in the material, processing and part validation. Dr Urko Gurmendi at Cikautxo says: “We believe that Arnitel HT will enable us to make important cost reductions and increase consistency and reliability in our production of high performance ducts. Our new ability to make better optimised parts in a single step provides us with a tangible advantage in the market.”
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