It took the automotive industry about five years to develop multilayer fuel tanks that could meet California's LEV II (low-emission vehicle) regulations in the late 1990s, said Mohammad Usman, who leads the computer-aided engineering and material department of Ford Motor Co.'s Powertrain Installations Division.
Stringent emissions standards — for cars and non-automotive small-engine equipment alike — and the transition to hybrid vehicles are some of the challenges facing carmakers and their suppliers today.
And even more-aggressive rules are coming, said Ford's Usman. The California Air Resources Board is currently working on LEV III, to be phased in over model years 2015 through 2025.
“I'm pretty sure that this requirement that's coming for the next 10 years is going to be much harder,” Usman said in a presentation last month at the Society of Plastics Engineers' Blow Molding Conference in Pittsburgh.
Hydrocarbon vapors must be fully contained in a fuel system that is entirely airtight, including the filler pipe, fuel lines and gas tanks, he said. “We want to contain everything in the system and then use it when we drive.”
The move to hybrid vehicles is also “challenging plastic fuel tanks in terms of performance requirements and the need to package batteries and tanks under the vehicle,” said Joel Kopinsky, managing director of ITB Group Ltd., a Novi, Mich.-based consulting company that tracks the global fuel-system business.
In North America, Europe and Japan, virtually all of the automotive plastic fuel tanks are extrusion blow molded, according to ITB. In North America, tanks are six layers and primarily made from high density polyethylene with an ethylene vinyl alcohol layer. In 2012, ITB projects that about 13.3 million North American vehicles will have been outfitted with HDPE tanks, Kopinsky said in a Nov. 8 email.
Washington-based American Chemistry Council data shows U.S./Canadian HDPE resin sales for blow molded auto fuel tanks up 15.7 percent for the first nine months of this year— at 195.2 million pounds — vs. the 2011 period.
Small-engine machines like mowers, blowers, boats and all-terrain vehicles are being hit with tougher emissions standards right along with cars and trucks, as the Environmental Protection Agency tightens federal regulations for that equipment.
In the fragmented, small-engine market, Kopinsky said, plastic fuel-tank technologies are diverse and, depending on the application, include blow molding, injection molding, thermoforming and rotational molding.
Materials used to produce those tanks include not only HDPE, but nylon and acetal.
In an Oct. 9 session on tanks at the SPE Blow Molders conference, speakers from Ticona Polymers Inc. and Lanxess Corp. discussed materials innovations for small tanks for motorcycles and small off-road engines for items like lawn and garden equipment and snowmobiles.
Ticona's acetal copolymer, known as Hostaform S POM (polymethylene copolymer), is used in single-layer blow molded fuel tanks. Ticona modified the backbone of the polymer to make a “much more durable, much more impact-resistant material than traditional POMs,” said George Zollos, POM marketing manager for Ticona in Florence, Ky.
Hostaform S POM meets tank emissions standards, according to Zollos.
“We're really in the early stages of introduction” to commercial markets, he said.
Maik Schulte, manager of global applications development for Lanxess Corp. in Pittsburgh, said the company's Durethan blow molding grade of nylon, BC 550 Z XBL, meets hydrocarbon permeation standards for small engines.
He said nylon fuel tanks can also be made by rotational molding, but they can exhibit brittle behavior and require long cycle times. Monolayer blow molded nylon also is an alternative to multilayer HDPE, steel and aluminum for tanks.
Another Durethan application is in-liners for compressed natural gas tanks, Schulte said.