Highly-filled polyamide-PBT blend provides stiffness in VW Touran air vents

  • Long slats with good surface finish and optimum dimensional stability
  • No additional paintwork needed
  • Blend of polyamide and PBT, 60% glass fibre reinforced
  • Part can be produced at mould temperature below 100° C

The German company Key Plastics Löhne, supplier of complete assemblies to the automotive industry, has developed a new air vent for the VW Touran that features longer slats than in any other vehicle type. The plastics distributor K.D. Feddersen provided material and support for this application.

Long slats with good surface finish and optimum dimensional stability

The material for the new slats had to have a good surface finish yet still possess a high degree of stiffness, while also offering good value for money. For all other models, Key Plastics already used a 50% glass fibre reinforced PA 6 compound with reduced moisture absorption from AKRO-Plastic. In this case, however, the stiffness was inadequate.The Hamburg-based plastics distributor K.D. Feddersen consequently recommended increasing the level of reinforcement to 60 percent, and the very first test using Akromid B3 GF 60 4 RM-M satisfied the customer’s requirements.

VW Touran air vent slats

Low moisture absorption results in good dimensional stability, thereby ensuring consistent operating forces during adjustment of the longer slats

Blend of polyamide and PBT

Akromid RM-M (mechanical types) is suitable for components subject to high mechanical stress. This product range offers only reinforced compounds with varying glass fibre content in three versions: standard, surface-modified (“9”) and with increased chemical resistance (“4”). The material is a blend of polyamide and PBT, combining the favourable properties of both polymers: the high degree of stiffness and low water absorption of PBT and the large processing window and very good surface finish of the polyamide. Precisely these properties were of key importance for the implementation of the new design with significantly longer slats. The reduced moisture absorption (1 %) is on par with partially aromatic blends. A further advantage of the material is that the tensile modulus is only slightly reduced and the slat therefore exhibits a consistently high degree of stiffness under a wide range of climatic conditions.

No additional paintwork needed

A very good surface finish with a high glass fibre content of 60 % is not easy to realise. Quite often the glass fibres are clearly identifiable on the surface. In this compound, the glass fibres are optimally bonded to the matrix and are hardly perceptible on the surface, thanks to the blend technology. The article and mould design also play an important role in ensuring that the ensuing component has a good surface finish despite the high degree of reinforcement. The material meets Volkswagen’s requirement of producing the component without additional paintwork and at a mould temperature below 100° C. The blend is thus a cost-effective alternative to partially aromatic polyamides.

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