Tough polymer at heart of green valve

The bobbin actuator on a valve that cuts smog-forming NOx emissions from exhausted fuel is made from a polymer that is strong, stable and does not creep at operating temperatures up to 240 C.

DuPont’s Zenite LCP is used to injection mould the bobbin that carries the coil for the electrical operation of the solenoid at the heart of the exhaust gas recirculation (EGR) valve developed by Siemens Automotive.

In addition to operating performance, the material keeps assembly costs to a minimum. Unlike a brittle thermoset, it accepts heatstaked metal parts. Low creep ensures that press-fit terminals are held firmly in place. Dimensional stability is crucial to an accurately wound coil that controls EGR valve operation.

The EGR reduces NOx by recirculating some of the gas back into the combustion chamber. Unlike vacuum-operated valves, an electrically operated EGR valve is controlled directly by the car’s on-board computer, giving faster, more effective valve response, as well as valve diagnostics.


Materials company Carilon, part of Shell Chemicals, is helping car makers to meet US emissions rules introduced at the start of the year.

Onboard refuelling vapour recovery valves (ORVRs) that cut hydrocarbon emissions at the petrol pump 30-fold to 0.2g/gal must be fitted to all new light vehicles on US roads by 2003, starting this year with 40% of new cars.

Carilon supplies GT Products, patentee of the ORVR device, with the unspecified polymer material used to make it. This is said to be more robust than polyesters commonly used in fuel systems, less brittle than acetal and more resistant to hydrocarbons than other materials tested.

GT says its ORVR, when fitted to fuel tanks, reduces emissions beyond the legal mandate.


A multi-layered sandwich material offers customised sound absorption and retention in areas of vehicles where conventional solutions would not work.

Vasco (vehicle acoustic shield composite) supplied by Salex Acoustic Materials is moulded to shape using low cost aluminum forming tools.