Fuel System Components and Aggressive Biofuel Environments

DuPont elastomers used in fuel system components help reduce permeation.

Global biofuel use is expected to double by 2015, according to “Global Biofuels Outlook 2009-2015” issued by Hart Energy Consulting.  With rapid population growth and a finite source of fossil fuels, the call to develop renewably sourced biofuels is clear, but that also places new demands on fuel system components. At the same time, automotive manufacturers are using technologies, including engine downsizing, direct injection, turbocharging and diesel engines, to meet more stringent emissions regulations and improve fuel economy.

But smaller, higher-performance engines, turbocharging, engine encapsulation, aggressive biofuels and more confined engine compartments generate hotter and tougher operating conditions for fuel system components, such as elastomers.

This has led to the development of a new generation of heat-, pressure- and chemical-resistant products within DuPont.

The Impact of Biofuels and Downsized Engines on Fuel System Components

Fuel system components and engine components must resist biofuels, temperature extremes and mechanical stresses for the lifetime of the vehicle. In particular, biofuels can be highly aggressive to the elastomers and plastics used in fuel system and engine hoses, gaskets and o-rings, inlet manifolds, ducts, valves and bushings — causing degradation, loss of sealing force, and eventual failure. Permeation and leakage through such components can be key sources of hydrocarbon emissions.

Ethanol-containing fuels can cause permeation, particularly in hydrocarbon rubbers such as nitrile rubber, thus increasing volatile emissions and fuel loss. Biodiesel can also attack nitrile and other rubber materials widely used in fuel-handling hose, gaskets and seals.

Meeting the Challenge with Elastomers

DuPont™ Viton® fluoroelastomers have been successfully used in seals and hoses for automotive fuel systems for over 45 years. Viton® has been shown to have broad compatibility with petroleum-based fuels and is a preferred elastomer for today’s sophisticated fuel injection systems.

DuPont and several leading fuels system OEMs have extensively tested different compounds of Viton® elastomers in pure ethanol, ethanol blended with hydrocarbon fuel, biodiesel, biobutanol and alcohol-based blend fuels.

The results indicate that fluoroelastomers offer the best permeation performance of traditional elastomeric sealing materials. Among the most dramatic findings, Viton® has been shown to be 1,000 times better than silicones (VMQ) and 100 times better than HNBR (hydrogenated nitrile butadiene rubber) in permeation resistance. It also has better heat aging and compression set resistance performance than either VMQ or HNBR.

Viton® elastomers also demonstrate excellent compatibility with biodiesel, and with ethanol; high resistance to permeation and chemical attack by alcohol, pure ethanol and blends of ethanol with hydrocarbon fuel; long-term retention of critical properties in current and emerging biofuels, and outstanding low temperature (-50°C to -65°C) static sealing performance in biofuels, (also at elevated temperatures).

DuPont™ Viton® fluoroelastomers (FKM) provide fuel permeation performance to meet new environmental regulations such as US CARB LEV II, EPA Tier II and PZEV, and European Euro 5. Viton® has long-term aging and compressive stress relaxation (CSR) performance to meet the 15-year life requirements — offering good low-temperature performance and excellent heat and compression set resistance when compared to traditional gasket materials such as HNBR and VMQ.

Stability of DuPont™ Zytel® Nylon Resins in Ethanol

Zytel® 612 nylon resins and Zytel® HTN high-performance polyamides have also demonstrated stability in ethanol and ethanol blend fuels and remain stable following immersion in E0, E10, E50 and 100% ethanol at 90°C for up to 2,000 hours, and can therefore be specified for applications requiring long-term service in fuels with ethanol content.

New Renewably Sourced DuPont™ Zytel® RS 1010 Nylon Resin in Biodiesel

DuPont™ Zytel® RS 1010 nylon can be used in diesel and biodiesel fuel lines. Debuting with Fiat, the renewably sourced long-chain nylon was chosen in preference to competitive grades of PA12 on the basis of its superior temperature resistance and long-term aging performance in biodiesel. It captured a “Most Innovative Use of Plastics” award from the Society of Plastics Engineers in the Environmental category.

DuPont Role in Biofuel Development

From seed to pump, DuPont is committed to being part of the solution for alternative transportation fuels by engaging throughout the biofuels value chain. DuPont has invested in two advanced biofuel technologies and continues to develop products to enhance the efficiency of existing corn ethanol plants, all to meet the global need for environmentally responsible, renewable automotive fuels.

DuPont’s Industrial Biosciences business is leading the way toward the commercialization of cellulosic ethanol with a fully integrated demonstration facility operating in Vonore, TN. This technology brings together DuPont’s extensive knowledge of production farming through its Pioneer® seed business, its broad applied experience in process design and engineering, and bioprocessing expertise powered by DuPont™ Genencor® science.  DuPont is designing and plans to build a commercial-scale, 28 MM gallon/year cellulosic ethanol facility in the town of Nevada, located in central Iowa. This plant will produce ethanol from corn stover collected after the annual harvest from local farms. DuPont is collaborating with corn crop producers to establish a biomass supply chain that generates agronomic value in addition to creating a high quality supply of raw material.

DuPont is partnering with BP through a joint venture, Butamax Advanced Biofuels, to commercialize biobutanol which has a higher energy density than ethanol, leading to up to 25% higher fuel economy.  Butanol can be blended with gasoline at higher concentrations in existing vehicles; it can also be blended at refineries and transported via existing fuel infrastructures.

In addition, through targeted Pioneer® hybrids, innovative enzymes and FermaSure® fermentation additives, DuPont offers first-generation ethanol plants ways to increase their efficiency in yield as well as uptime, thereby making first-generation biofuels more competitive and more sustainable.

As the industry leader in automotive materials including fuel system components, DuPont will continue to collaborate with automakers, OEMs and energy companies to find innovative, sustainable solutions to face the global challenge of reducing dependence on fossil fuels.