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Automobiles enhance use of plastic for fuel tanks but are slow in adapting it for fuel lin ...
 
Plastic fuel tanks in automobiles are gaining usage globally. Blow moulded or injection moulded multi layer HDPE fuel tanks are most common. The automotive industry has made significant developments to meet the recent emission standards.

However this trend has not been increasing globally in a geographically uniform pattern. Europe has almost fully converted to these plastic fuel tanks, with 92% automobiles of European origin fitted with plastic fuel tanks. North America, with 75% usage, is lagging behind. However, the Asian region is lagging far behind, due to problems of economies. One of the possible reasons is the smaller number of car produced in different parts of Asia as compared to Europe and North America. The use of plastic fuel tank does not become economical at lower production levels of an individual automobile company.

Another development in the auto segment has been plastic fuel lines that convey fuel from the tank to the engine compartment. Compared with existing rubber and steel fuel lines, plastic fuel lines are lighter in weight, lower in cost and often less permeable. They are also available in many colors, which make it easier to place, track and connect fuel supplies. Interestingly, the automotive companies are very slow in making the switch to plastic lines. The slower pace stems from concerns by auto companies over the ability of plastic fuel lines to meet strict air emission standards, and to resist electrostatic discharges (ESDs), which could ignite flammable fuels. Automakers also need to be convinced that fuel lines made of plastics can withstand the impact of crashes at low winter temperatures and can resist degradation from alcohol fuels. But polymer suppliers and Tier One auto manufacturers have developed new fuel line materials and designs, which they believe can meet these challenges.

The most common polymer used in plastic fuel lines is polyamide, often combined in multilayer structures with fluorocarbon polymer barrier resins. Another low-permeability material that has been paired with polyamide in multilayer structures is polybutylene naphthalate (PBN). Aliphatic polyketones have also been promoted as fuel line materials. Some polymide based fuel line formulations include low levels of carbon nanotubes, which enhance ESD properties without harming physical properties.

Complying with increasingly stringent antipollution regulations is the biggest challenge faced by developers of plastic fuel lines and other plastic fuel components such as tanks, pumps, vapor recovery systems, filter pipes and fuel rails. Of most concern to the global auto industry are regulations in the U.S. state of California that limit the levels of hydrocarbons auto fuel system can release into the air. Among them are the ZEV (zero emission vehicle), PZEV (partial zero emission vehicle), and the CARB (California Air Resource Board) LEV (low-emission vehicle) II standards. Some of these rules have already taken effect; others will be phased in over the next few years. Because California has traditionally set the pace for air pollution regulations in the rest of the U.S. and elsewhere, most of the world's car manufacturers are striving to meet the standards in that state.

To meet the new air quality standards, plastic fuel line manufacturers have developed structures that reduce vapor permeation through their walls.
Atofina Chemicals Inc. has developed tubes made from Rilsan line of polyamide 11 and 12, with barrier properties enhanced by coextrusion with Kynar PVDF (polyvinylidene difluoride). The layers are held together with an adhesive tie resin. Features of Atofina's new conductive grade of the Rilsan polyamide 12 polymer include a surface resistivity below 105 ohms which meets the conductivity requirements of SAE standard 2260, and impact resistance down to -40° C.
Dana Corp. has commenced production of new multilayer plastic fuel line systems for automotive applications in Europe, North America and South America. The five-layer tubes have a PBN middle layer, two adhesive layers, and nylon 12 internal and external layers.The PBN-based materials are lower in permeation rates, cost and weight than polyamide/fluoropolymer multilayer fuel lines, and help in ahieving 2006 PZEV requirements.
In Japan, Ube Industries and Asahi Glass, have jointly developed a two-layer fuel line material composed of nylon 12 and a ETFE (ethylene tetra fluro ethylene ), a barrier resin. The two layers in their resin system adhere strongly without the need for adhesive tie layers, which can deteriorate over time and cause delamination, and are reported to remain intact and undetached even after 1,000 hours of immersion in alcohol-based fuel. Other features include little fuel permeation or vaporization, and excellent machinability and chemical resistance.
DuPont's product line known as Selar RB amorphous nylon can be dry blended with polyethylene to create monolayer fuel tanks, fuel lines, filler necks and filter housings that meet LEV II emission requirements.
SRI International is offering for license a high-performance aliphatic polyketone, tradenamed Carilon, that combines good chemical and permeation resistance with superior impact strength and high-temperature performance.

New ways for improving the ESD properties of fuel lines are also emerging. The typical approach for making a plastic fuel line static dissipative is to add graphite fibers to the resin formulation. But this can degrade the polymer's properties, particularly its impact strength. A newer practice is to make fuel line resins conductive with much smaller particles (carbon nanotubes).

Will these new material/product innovations accelerate the use of plastics in fuel lines?

 
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