DuPont Performance Polymers: one stop for essential plastics and elastomers solutions in air management
DPP offers the industry's broadest range of plastics and elastomers for key air management applications including air intake manifolds and gaskets, air ducts, turbocharger hoses and resonators, exhaust gas recirculation seals, hoses, valves, bushings, and sensor seals.
The global recession has presented the automotive industry with one of its greatest challenges, but also with opportunities for the most innovative to flourish. In such a period of change, automakers look to new technologies and better materials to meet the new market forces, driven by economic and environmental needs.
Engine downsizing, lightweighting, turbocharging, direct injection, and exhaust gas recirculation are all responses to the drive for greater fuel economy, higher engine efficiency and lower CO2 emissions. But these advances come at a price. They generate more heat, and involve more aggressive gases, fluids, and acidic gas/air mixtures, often under high pressure. Many traditional materials of construction can no longer perform in the much hotter, confined and stressed environments created by the modern engine.
This article focuses on automotive air management - a critical engine system undergoing particularly rapid change - and reviews the latest solutions in plastics and elastomers for air management components.Air management systems integrate many components, including the turbocharger, resonator, intercooler, air intake manifold, exhaust gas recirculation and closed positive crankcase ventilation systems with air ducts, hoses, seals, gaskets, bushings and membranes to connect and seal these components.
Air management systems integrate many components, including the turbocharger, resonator, intercooler, air intake manifold, exhaust gas recirculation and closed positive crankcase ventilation parts. |
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These vital components require exceptional materials to withstand the high mechanical stresses, extremes of heat and cold, and aggressive chemical environments for the lifetime of the vehicle. They must also be sustainably produced, and help automakers meet ever more stringent global evaporative emissions legislation - including US PZEV Phase III, LEV II, and Euro 5 and 6 - by demonstrating low to zero permeability to engine gases and fluids.
Who does the automotive industry turn to in its quest for plastics and elastomers designed specifically to perform in the tough service conditions? Among several leading materials suppliers, DuPont Performance Polymers (DPP) stands out by offering the industry's broadest portfolio of products for automotive applications.The company delivers cost-effective solutions in vehicle systems that lower CO2 emissions, reduce oil and fuel consumption, use alternative energy, and enhance performance so automakers can create the cars consumers want to buy.
DPP is currently the only company able to supply one-stop rubber and plastic solutions for many key air management components like air ducts, integrating from one side Vamac® AEM acrylic rubbers and Viton® fluoroelastomers, often reinforced by Kevlar® para-aramid fiber or Nomex® meta-aramid fiber, and from the other side the stiffer Zytel® PA6, 6 and PPA polyamides and the softest Hytrel® TPC-ET thermoplastic polyester into welded, injection or blow-molded parts that can save up to 50% in weight, and over 20% in cost compared with metal parts.
Chart shows relative heat and oil resistance of the key rubber materials used by the automotive industry, illustrating the high performance of fluoroelastomers like Viton® at the higher end of resistance. |
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The company is also at the forefront of materials development and testing to resist acid condensates in exhaust gas recirculation (EGR) systems, with the objective of helping OEMs reduce weight, and meet legislation requiring particulates and CO2 emissions reduction. DPP has become a key supplier to the auto industry OEMs, providing elastomer and resin solutions in air management. Following is a review of the the DPP products best suited to key air management system components - (1) by product selection and (2) by application - and reports on some notable commercial programs.
DPP product families most widely specified for air management applications range from rigid high performance plastics - Zytel® nylon resins and high performance polyamide, and Vespel® polyimide parts and shapes, through Hytrel® thermoplastic polyester elastomer offering the flexibility of rubber and the strength of plastic, to the VSolutions flexible elastomers - Vamac® ethylene acrylic elastomer, and Viton® fluoroelastomer.
DPP resins and engineering polymer products Hytrel®, Vespel® and Zytel® offer the highest performance in lightweight materials enabling innovative metals replacement, dependable mechanical properties, low friction and low emissions characteristics to help reduce oil and fuel consumption while improving auto performance. |
Click to enlarge the Picture / Chart grades are engineered for extremes and retain stiffness, strength and mechanical properties despite exposure to high temperatures, long-life coolant, chemicals and moisture. The high performance polyamide can help reduce weight and cost, and enhance performance of components in automotive air management systems.
nylon maintains excellent performance levels much longer than traditional nylon despite exposure to hot oil, hot air, calcium chloride and other aggressive automotive chemicals. It is intended to take out weight and cost by replacing metal, and contributes to engine weight reduction.
Zytel® is broadly specified for air ducts and turbo air ducts, air intake manifolds and gaskets, resonator housings and charge air coolers.
and shapes provide stiffness, tensile strength, and resistance to friction, wear and hot exhaust gases at temperatures up to 220°C. Its very low coefficient of thermal expansion and its excellent formability during injection molding permits thinner-wall constructions, and its considerably lower density than brass or steel can result in components of significantly lighter weight.
Vespel® can be found in turbocharger hose and EGR valve bushings.
provide the flexibility of rubbers, the strength of plastics, and the processibility of thermoplastics. Hytrel® HTR4275, a specially-modified blow-molding grade with an increased melt viscosity, a hardness of 55 Shore D and a relatively high stiffness of 170 MPa at 23 °C and 60 MPa at 100 °C, combines good mechanical properties at high temperatures – a prerequisite for air ducts – with high elasticity across a broad temperature range. All Hytrel® grades offer long-term resistance to hydrocarbons and other automotive fluids and gases.
Air ducts of Hytrel® are specified as standard equipment by virtually all OEMs worldwide, and have been fitted to over 80 million vehicles to date, including Audi, Fiat, Ford, GM, Jaguar, Land Rover, Nissan, Porsche, PSA, Renault, Saab, Seat, Suzuki, VCC, and Volkswagen.
(AEM) are high performance heat and fluid resistant elastomers for flexible automotive seals, hoses, gaskets and molded goods offering significant performance advantages over low temperature standard ACM and HNBR, including better low and high temperature resistance up to 175°C, and offer substantial cost savings compared with HNBR.
Vamac® is widely specified for molded turbo air ducts, turbocharger hoses, intercooler seals and other flexible sensor hoses, seals and connectors like closed positive crankcase ventilation systems, and, in the future, for low pressure EGR systems.
Seals of Viton® fluoroelastomers retain sealing force over a temperature range from -40°C to +230°C even during exposure to hot air, gasoline and diesel fuels. |
(FKM) are the most specified fluoroelastomers for tough automotive sealing applications. Seals of Viton® retain sealing force over a temperature range from -40°C to +230°C even during exposure to hot air, gasoline and diesel fuels.
Viton® is the elastomer of choice for air intake manifold gaskets, and offers the lowest permeability to fuel of all elastomers used commercially. Viton® is the best choice for an elastomer to meet LEVII and PZEV emissions regulations.Viton® is also specified extensively for turbocharger hoses, sensor seals, air intake manifold gaskets and other flexible hoses, seals and connectors where heat, fuel and acid exposure requirements are severe.
Today's trend to smaller, more fuel efficient and higher performing engines owes much to turbocharging. The latest turbocharged engines, both diesel and gasoline, deliver superior performance and transform more of the fuel energy into power than normally aspirated engines. Modern turbocharging is an efficient way to meet Euro 5 and 6 emissions legislation, reduce fuel consumption and improve vehicle economics.With increases in engine power and performance come big hikes in temperatures and pressures. Turbocharged diesel engines expose hot side turbo hoses to higher temperatures above 165°C up to 220°C and pressures of 2.5 bars. And the trend towards higher compressed air pressure is expected to lead to even higher operating environments in the next few years.
This temperature evolution is causing turbo hose manufacturers to switch to higher performing elastomers. Traditional CM, CR, ECO or NBR/CR materials have been rapidly displaced by standard AEM, HT-AEM and HT-ACM. However, even these polymers fail at continuous exposure above 185°C.
Turbocharger hose construction offering |
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High performance specialty fluoroelastomers like Viton® can withstand temperatures up to 230°C in aggressive engine oils for the lifetime of the vehicle. DPP has developed a range of formulations based on Viton® for FKM/silicone turbocharger hoses that combine excellent extrusion properties and processability with optimum balances of heat and oil aging resistance, as well as low temperature flexibility and opportunities for silicone adhesion.
The turbo revolution is also becoming a major success story for high temperature Vamac® HT AEM— a key material of construction for turbocharger hoses, particularly in replacement of silicone rubber (VMQ) and polyacrylic (ACM).
Vamac® is specified for turbocharger hoses for continuous temperatures as high at 175°C, peaking as high as 190°C. |
Fiat is using HT-AEM including new Vamac® Ultra HT (=VMX 3038) for the class F (continuous temperature = 170°C) of their new turbo hose material specification Fiat 9.02132/01.
Air ducts operate in a hot and stressful environment involving heat, pressure/vacuum, engine oil and blow-by-gases - conditions that can induce rapid heat aging in many plastic and rubber materials.Specific grades of Hytrel®, Vamac®, Viton® and Zytel® are available for turbo air duct components. The selection of product and type depends on function and operating conditions. For example, is the duct positioned on the hot or cold side of the intercooler? What degree of flexibility is required? Will it integrate with other materials?, etc. Our engineers help OEM’s select and develop the best solution for a specific application.
Stiff yet elastic DuPont™ Hytrel® HTR4275 is being used in a new two-component air duct from system supplier Mahle of Stuttgart, Germany, that connects the intercooler and throttle body of BMW’s three liter, six cylinder twin-turbo engine. Reducing the part to just two basic components has led to lower weight, more efficient production and assembly, and a significant cost advantage over the earlier model of glass-fiber reinforced nylon and elastomers. Used on the cold side of the engine, the innovative air duct consisting of two Hytrel® sections is one of the first mono-material solutions of its kind in Germany.
New two-component air duct of DuPont™ Hytrel® from Mahle for the BMW three liter, six cylinder twin-turbo engine consists of lower duct section A, and upper duct section B. The integrated bellow counters any movement between the vehicle and engine, and permits flexibility for assembly. |
The stiffness, strength, temperature, chemical and load-bearing resistance of Zytel® makes it a prime candidate for air duct development. Several major OEMs are currently developing air ducts of Zytel®.Key auto applications for Vamac® and Viton® include molded air ducts before the turbo, and hot and cold side turbo hoses after the turbo and intercooler.
Charge air coolers, also known as intercoolers, cool engine air from the turbocharger before it enters the engine. Components in this unit must accommodate wide temperature variations, hot air under pressure, vibration and mechanical stresses.Zytel® glass reinforced nylon 66, Zytel® HTN and Zytel® PLUS are proving ideal candidates for this demanding air management application, enabling weight and cost reduction in replacement of traditional materials.
New DuPont™ Zytel® PLUS nylon helps reduce weight and cost in charge air coolers, exhaust mufflers, turbo air ducts, engine mounts, resonators, cylinder head covers, oil pans, EGR coolers, oil modules, thermostats, transmission components and radiator end tanks, while maintaining excellent performance levels much longer than traditional nylon despite exposure to hot oil, hot air, calcium chloride and other aggressive automotive chemicals. |
Vamac® is often used for intercooler seals, while Viton® has been specified for more severe technical requirements.
EGR systems, designed to reduce oxides of nitrogen (NOx) from exhaust emissions, recirculate already combusted exhaust back into the air intake to dilute the incoming air/fuel mixture, thus reducing combustion temperatures well below the 1300+°C peak at which NOx is formed. However, recycling exhaust gases back into the engine results in gas compositions that are very aggressive to many sealing elastomers.
Vamac® ethylene acrylic elastomers and Viton® fluoroelastomers are at the forefront of developments in flexible hoses and hose-end seals, providing long-term temperature and acid resistance for these key EGR applications. |
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Vamac® and Viton® can meet demanding flexible hose, seal and connector specifications for low pressure EGR system applications. Standard recipes based on Vamac® and optimized recipes of Viton® both demonstrate excellent resistance to exhaust acids and gases.
Vamac® provides a cost-effective EGR hose and sealing solution at peak temperatures up to 150°C, while Viton® can be considered the primary candidate for highly concentrated acid environments at peak temperatures up to 225°C.
In rigid EGR applications, valve bushings of Vespel® TP polyimide have replaced metal components because of its stiffness, tensile strength, and resistance to friction, wear and hot exhaust gases at temperatures up to 220°C. The valve bushings, made by Gustav Wahler GmbH and Co. KG of Esslingen, Germany, for an EGR system used in four and six-cylinder stratified-charged petrol engines, position and guide the cylindrical operating rods of EGR slip-in valves, supporting their smooth operation during millions of openings and closings.
Low wear, low friction injection molded bushings of Vespel® TP polyimide for EGR valves manufactured by Gustav Wahler for four and six cylinder petrol engines, offer increased design freedom, reduced weight, elimination of contact corrosion and increased resistance to aggressive exhaust gases when compared to similar metal bushings. |
The air intake manifold (AIM) distributes air into the cylinders of a direct injection engine, or an air/fuel mix in a non direct-injection engine. It is an increasingly difficult sealing challenge for the automotive designer in view of more stringent emissions requirements, demands for longer fuel system life, higher engine temperatures and new manifold materials. AIM units were typically made of aluminum or cast iron, but the trend is to plastics and elastomeric sealing.Viton® AL, the fluoroelastomer type best suited for AIM gaskets, excels in low permeability far surpassing that of HNBR, VMQ (silicone) and FVMQ (fluorosilicone), and compression set resistance, ensuring long-term retention of sealing forces. It offers the lowest permeability to fuel of all elastomers used commercially, in compliance with LEVII and PZEV emissions regulations.
Figure 1. shows rate of permeation of fuel through gasket elastomers, and clearly indicates the superior resistance of Viton® AL and F types compared with HNBR and silicone. In Figure 2. Viton® AL exhibits essentially no elongation loss after heat aging at 3000 hours at 150°C versus silicone and HNBR. |
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Viton® GAL-S and Viton® GLT-S are the fluoroelastomers of choice for better low temperature performance, and especially for higher resistance to aggressive biodiesel and acid exhaust gas fumes recirculating in the air intake manifold via the EGR high pressure loop.
AIM gaskets and O-rings of Viton® (blue) offer the lowest permeability to fuel of all elastomers used commercially, in compliance with LEVII and PZEV emissions regulations, and enable simplified AIM constructions. |
AIM seals made of Viton® remain resilient and retain sealing force over a temperature range from -40°C to +230°C even during exposure to hot air, gasoline and diesel fuels, including blends with methanol, ethanol and oxygen-containing additives. Retention of sealing force at very low temperatures (-40°C) helps prevent air in-leakage.
The trend to smaller and less complex AIM structures and higher temperatures and pressures has also favored Zytel® for rigid AIM components.
Turbocharger resonators act as mufflers to reduce the pulsating turbo whine from the turbocharger and change the frequency of the sound to a lower, more pleasant register. Resonators operate under high pressure and temperature, conditions suited to Zytel® HTN.
Hot turbocharger resonator housing of Zytel® HTN, developed and molded by Umfotec GmbH for 1.6 and 2.0 turbo-diesel engines produced by a major German OEM. |
Zytel® HTN has been specified for a hot turbocharger resonator housing developed and molded by Umfotec GmbH, and fitted as standard equipment to 1.6 and 2.0 liter turbo-diesel engines produced by a major German OEM.
Oxygen sensor (or lambda sensor) seals play a key role in engine performance and pollution reduction by monitoring the level of oxygen in the exhaust so the air/fuel mixture can be regulated to reduce emissions. The unit is mounted in or near the exhaust manifold downpipe ahead of the catalytic converter and is exposed to hot, aggressive exhaust gases.Viton® fluoroelastomers - and sometimes Kalrez® perfluoroelastomer parts - are used for oxygen sensor seals because of the requirements: excellent long-term sealing performance coupled with resistance to hot exhaust gases and temperatures over 225°C to 300°C.
DuPont Automotive offers more than 100 materials and products to the global automotive industry and through its global applications network is committed to delivering cost-effective solutions to help reduce vehicle weight for better fuel economy and CO2 emissions reductions, to integrate part functionality to simplify assembly and eliminate cost, and help bring invention to market quickly, cost effectively.For more information, contact us.
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