New Nylons Boost Performance under the Hood

The first major application for a new DuPont nylontechnology is an engine cover for a new-generation turbocharged engine used inthe 2010 Cadillac CTS.

The result is a cost savings of up to 30 percent and animproved appearance. DuPont has filed more than 20 patent applications forvarious aspects of the new nylon technology.

A longtime workhorse engineering plastic, nylon is thetarget of a research renaissance, much of which was on display at K 2010, a German tradeshow held Oct. 25through Nov. 3.

Much of the research is focused on boosting the thermalperformance of nylon in under-the-hood applications, where resistance to hotoil, engine coolant and road salt is also required.

"One of the most prevalent trends in the automotivemarket is the use of turbocharged engines for smaller cars," says Mike Day,DuPont Automotive Performance Polymers marketing director-Americas.

A turbocharger is a gas compressor that increases thedensity of air entering the engine to create more power. The compressor ispowered by a turbine driven by the engine's own exhaust gases rather than a directmechanical drive.

The result is that thermal specifications for the GMengine cover are 180C for continuous use and 200C peak with exposure to hotoil, coolants and road salt. The new nylon grade works at 210C continuoustemperature and 230C peak.

"We find most often in our turbo charge and otherhigh-temperature applications that the continuous temperature range is higherthan what standard nylons may be able to tolerate," says Shawn Owen, seniorproject engineer for the GM Power Train Air Delivery Group.

"So typically, we have been using polyphthalamide (PPA)materials that come with cost, appearance and processability concerns. For sometime, we've been looking for a replacement."

FastProcessing

GM materials' engineers also require plastic for the newapplication to have excellent surface finish with potential for flame-retardantapplications. To meet part economics requirements, the plastic must also moldin cycles under 60 seconds. Total cost savings to GM are as high as 30 percentwith the new material.

The engine cover was recognized as the materials' categorywinner in the 2010 Society of Plastics Engineers Automotive Innovation Awards Program. Winners wereannounced Nov. 9 in Livonia, MI.

The nylon used in the engine cover is Zytel Plus PLS95G35DH copolymer - extended HS. It's based on "Shield" technology which DuPontintroduced at K 2010 in Dusseldorf, Germany.

DuPont describes Shield as its most important nylondevelopment in 30 years. A DuPont scientist named Wallace Carothers inventednylon in 1935. Outside the U.S., nylon is called polyamide.

There are three components to Shield technology: newpolymer backbone, polymer modifications and a new set of additives.

DuPont officials feel the GM engine cover is the tip ofthe iceberg. Oil pans are another target. Oil pans have been slow to convert toplastics because of tough stone-impact requirements.

Another new Zytel Plus grade is designed specifically tomeet aluminum stone impact and heat-aging requirements. Its designation is ZytelPLS 95G40DH1t. The new grade may also create opportunities for plastics inautomotive exhaust systems. Other targets are transmission pans, oil filtermodules, rocker covers and other transmission components.

DuPont also introduced two new PPA grades at K 2010 thatuse Shield technology. The new Zytel HTN92 Series PPA resins feature strengthafter 1,000 hours air oven aging at 230C that is double that of standard PPA,according to a DuPont spokesperson at K 2010.

NewHR Grade

BASF nylon technology is also making news.

A new engine-mounted oil filter module is enabled by asuperior hydrolysis and heat-aging resin. The part is used on the 2011 ChryslerPentastar engine. The resin is a 35 percent glass-filled Ultramid optimized forhydrolysis resistance. The HR resistance is improved by a specialized coatingon the glass fiber.

Thermal requirements for cooling systems have been risingdue to higher under-hood temperatures - the same factor affecting engine coversand other components. Testing temperatures have increased to 130 to 135C. Thenew module is directly mounted and packaged in the engine. The previous systemwas remotely mounted in a cooler environment. Like the DuPont material, thebase resin is also modified to increase chemical resistance.

First use of the new module by an American OEM is on the 2011Dodge Challenger and the 2011 Jeep Grand Cherokee.

In another development, nylon composites are used asweight-saving engine mounts in the BMW 550i GT and 750i. Force-transmittingcomponents of engine mounts have been made of metal, first steel and morerecently, die-cast aluminum.

Use of glass-reinforced nylon reduces weight 50 percent,eliminates one supplier, and reduces noise levels. In a presentation in AuburnHills, MI, Scott Bykowski, manager R&D for ContiTech North America, said theBASF application represents the first use of injection molded nylon for achassis cross member.

The transmission cross beam is a structural component designedto withstand high load and is the direct link to the engine-transmission mount.

BASF also announced major nylon innovations at K 2010.

One example is a new fast-flowing nylon 6 compound,Ultramid B3WG6 High Speed. In spiral flow tests, the new grade flows at least50 percent farther than its conventional predecessor, according to BASF.

"The benefits associated with good flowability canbasically be exploited in two different situations," says Dr. Anka Bernnat, anautomotive product development specialist for BASF in Ludwigshafen, Germany.One is reduced wear on tools. In another benefit, more complex geometries inmolds can be filled more easily. The new chemistry will also target enginecovers as well as intake manifolds and pedals.