DuPont Zytel goes on exhaust bracket

Anvisgroup of Germany, working in cooperation with Volkswagen, has developed the first catalytic converter bracket for cars to be made from an engineering thermoplastic.

Due to its close proximity to the engine with temperatures up to 175deg C, high static and dynamic forces, moisture and chemical exposure, steel plates had previously been considered irreplaceable for such applications. Yet anvisgroup has proven the opposite by developing an innovative, two-component bracket based on glass-fibre reinforced DuPont Zytel nylon and rubber. Since mid-2006, this design has proven itself at the ‘hot end’ of exhaust systems on all new vehicles belonging to Volkswagen’s Golf platform (PQ35).

Manufacture of the newly-designed bracket starts with the injection-moulding of the cross-bar in Zytel. During a second production phase, the rubber bearings, either made from EPDM (for diesel and smaller petrol engines) or the more heat-resistant silicon rubber VMQ (high-performance petrol engines) are moulded on. Finally the aluminium bushings, required to secure the bracket, are assembled by force fitting.

Mounted between the exhaust manifold and the catalytic converter, the two-component part provides flexible and attenuating support for the exhaust system in the x-direction, while absorbing static and dynamic loads in the y- and z-directions.

Comprehensive testing, carried out by anvisgroup, showed that Zytel 70G35HSL, a hydrolysis-stabilised PA66 with 35 wt percent glass fibres, can meet OEM requirements for dependability for the entire lifecycle of the vehicle.

The new design has other decisive benefits: Firstly, the polymer component weighs only 165g and is much lighter than its 300g metal counterpart, leading to fuel savings. Secondly, it provides the opportunity for cost-efficiencies during manufacture as surface protection is no longer required to prevent corrosion.