Polymer fuel tanks to meet emission standards
Fuel tanks that help motorcycle manufacturers meet stringent emission standards in the USA are on their way thanks to research conducted at the Polymer Processing Research Centre (PPRC) at Queen’s University Belfast, UK.
International polymer suppliers Total Petrochemicals and Arkema Inc, both headquartered in the USA, approached researchers at the PPRC to investigate rotational moulding of new types of polymer materials for use in fuel tanks.
High fuel barrier materials are required to meet regulations passed by the US Environmental Protection Agency (EPA) in 2002, in accordance with the federal Clean Air Act. From 2008, all new motorcycles and recreational vehicles, such as snowmobiles and dirt bikes, must have fuel permeation rates of less than 1.5g/m2/day. Conventional blow-moulded high-density polyethylene tanks have rates greater than 8g/m2/day.
The new Petro-Seal technology creates multilayer tanks with an inner barrier layer of Rilsan polyamide 11 resin and an outer shell of metallocene polyethylene. Both resins were developed to enhance adhesion between the layers.
Mark Kearns, Moulding Research Manager at the PPRC, says, ‘We optimise the processing of the tank materials – what you can and cannot do. There are subtleties in the required temperatures for each material, the addition of the second layer [using a drop box] and the overall part cooling.’
The result is a tough, low-cost machineable tank that, Arkema claims, meets the new emission standards.
Kearns explains that although many manufacturers in Europe still use metal tanks, in North America, the trend is towards polymer tanks, and manufacturers are not keen to return to the ‘heavier’ metal varieties. ‘There is a push away from metal tanks because if there is a crash, there may be sparking. Polymers also improve impact and corrosion resistance, and are more cost effective,’ says Kearns.
He adds, ‘I would not be surprised if these new tanks were used in Europe in three to five years.’ Motorcycle emission regulations are not as stringent in the UK. Yet, according to the EPA in the US, ‘motorcycles produce more harmful emissions per mile than a car’.