demands to dramatically improve fuel economy are putting pressure on automotive
engineers to find lighter, better-performing materials for hotter, smaller
engines and lighter power trains.
prices, increasing environmental awareness and changing political conditions
are more and more focusing attention on the energy efficiency of automobiles," says
Martin Baumert, team leader for automotive product development for BASF's
engineering plastics group.
The U.S. will
require a passenger car fleet average of 36.7 mpg in the 2015 model year, a
hike of about 40 percent from the 2010 model year.
responding with turbocharged engines in which the pressure of air entering the
engine is boosted to create more power. European manufacturers such as Volvo,
Saab and Volkswagen have made widespread use of turbocharged engines in recent
OEMs are catching up fast. For example, the 3.5-l„“ Ford EcoBoost V6 debuted in
four models, including the 2010 Flex. A 2.0-l„“ EcoBoost four-cylinder engine in
the 2011 Explorer gets 30 percent better gas mileage than the 4-l„“ V6 it
are trying to surround the new engines with plastics that can reduce weight, take
the heat and meet chemical-resistance requirements.
goal for design engineers is metal replacement," says Bill Gaines, automotive
industry manager for Solvay Advanced Polymers.
A weight reduction
as high as 50 percent can be achieved with plastic-for metal substitution,
according to industry estimates. A weight reduction of 220 lb (100 kg) cuts automotive
fuel consumption by roughly one-tenth of a gallon per 62 miles traveled.
One example of
load-lightening is a direct replacement of die-cast aluminum in mechanical
water pump housings with Amodel
polyphthalamide (PPA), a semi-aromatic polyamide (nylon).
mechanical water pumps had to be made of die-cast aluminum because of their
size," says Brian Baleno,
a global automotive marketing manager for Solvay
Advanced Polymers. "But now as engines are being downsized, other components
can also be downsized, reducing their loads. And now the loads allow for the
use of thermoplastics."
It's a good
fit for PPA because its semi-aromatic structure provides resistance to moisture
absorption. Hybrid cars are using electric water pumps, whose load can easily
accommodate use of plastics.
estimates that Amodel is growing organically at about 10 percent a year as a
result of new engine designs. Part of the growth is coming from Asia.
applications that typically use water and ethylene glycol are the sweet spot
for PPA applications. Hot Polyamides
but improved, polyamides are gaining ground in applications that require heat
resistance but don't require as much chemical or moisture resistance. Target
applications are intercooler caps, resonators, charge-air lines, throttle
valves and intake manifolds with integrated water-cooled intercoolers.
Motors chose a revamped polyamide technology for an engine cover in a
new-generation turbocharged engine in the 2010 Cadillac CTS. GM had used PPA in
operating temperatures for this application are higher than what standard
nylons can stand" says Sean Owens, technical leader for GM Powertrain. "We have
been looking for lower-cost alternatives."
specifications for the engine cover are 180C for continuous use and 200C peak.
He chose a new nylon grade developed by DuPont that works at 210C continuous
temperature and 230C peak.
nylons are said to reduce system costs in the range of 10 to 30 percent,
according to the nylon suppliers. One advantage over PPA is that cycle times
are shorter. PPA requires oil cooling of injection molds and is also available
in grades that can be molded in water-cooled tooling.
engineers also require polymer candidates for the new application to have
excellent surface finish with potential for flame-retarded grades. To meet part
economics requirements, the plastic must also mold in cycles under 60 seconds.
"There is a
key cluster of potential applications in the air induction system," says Klaus
Bender, global powertrain lead for DuPont Automotive. "The EGR (exhaust gas
recirculation) system is on the radar screen." The second commercial
application for Zytel Plus is an EGR system component for a turbocharged diesel
engine (inline four-cylinder).
percent glass-reinforced plastic must withstand continuous temperatures of 190C
and peak temperatures in the range of 210 to 230C. Zytel Plus is replacing
die-cast aluminum. One OEM is actively investigating the potential to use the
new high-heat nylon in a key structure of the EGR.
higher-heat, glass-reinforced polyamide was introduced at K 2010 by BASF.
Ultramid Endure easily withstands continuous use at temperatures up to 220 as
well as spikes up to 240C," says BASF's Baumert. "This extends the field of
application of polyamides into the high-temperature realm."
comparison, the previous BASF polyamide - Ultramid A3WG7 - with the same
glass-fiber content has a long-term service temperature of 170C, while heat-resistant
PA 66/6 grades (Ultramid W2 or Ultramid A3W2G6) can withstand 190C in
improvement in resistance to heat aging is achieved through stabilization
technology developed by BASF. Formation of a protective surface layer even at
temperatures up to 220C provides continuous protection against attack by
estimates that up to 3.3 lb (1.5 kg) of Ultramid Endure can be implemented into
a car near the turbocharged engine.
examples of other materials' technologies gaining traction in demanding
using Victrex polyetheretherketone (PEEK
) polymer to
replace metal in an innovative gear design that reduces weight and boosts
traditional iron and steel gears, the Victrex PEEK polymer gear gives us about
70 percent less inertia and weight," says Aaron Clark, engineering manager for
Metaldyne Powertrain Products. "That's important because lower weight and
inertia gives us about a three to nine percent reduction in power consumption
which results in improved fuel economy in the vehicle."
shaft modules in the gear design are used to cancel the inherent shaking forces
associated with inline four-cyclinder engines.
modules spin at twice engine speed - up to 15,000 rpm - polymers are not
normally used," says Clark. "The maximum operating temperatures in four-cylinder
engines are approaching 155C (311F) and most polymers can't survive in these
at 155C (311F) and also maintains its material properties including fatigue
strength, chemical resistance, high temperature resistance and strength,
according to Victrex.
they are injection molded, the Victrex PEEK polymer gears require no post
machining and this eliminates the need for grinding equipment," says Clark.Ford's Polimotor
interesting development, Torlon
first developed by Union Carbide, is making a comeback in cars.
Engineering Plastics Products describes Torlon as the highest-performing
melt-processable plastic. It can perform at severe stress conditions at
temperatures up to 500F, according to Quadrant, which is a plastics processor.
engine developed by Polimotor Research with Ford in the 1980s used Torlon for
the engine block and other important components. Use of carbon-reinforced Torlon
for the valve stems in place of steel reduced weight more than 75 percent,
according to Amoco Chemicals, which owned Torlon at that time. Torlon valve
spring retainers weighed
only 9 gm each versus about 22 gm for steel.
weighed 153 lb versus 415 lb for its iron counterpart. It was an amazing
technical advance, but it never made it to production vehicles because it was
too big a risk for mainstream car manufacturers, which had substantial
investment in the metal casting and other processes still used to make engine
companies are using the composite casting process developed by engineer Matty
for the Polimotor project. They aren't using Torlon, however.
Their composites are based on phenolic, a thermoset resin with good thermal and
chemical resistance properties.
Torlon is again in the conversation under the hood.
been making a comeback in the last four-to-five years," says Bill Gaines of
Solvay Advanced Polymers, which bought Torlon and other engineering plastics
from Amoco Chemical.
"One of the
growth areas for Torlon is in the compressor side of the turbocharger," says
Baleno. Sealing applications are the first target. Compressor wheels may also be
made of Torlon at some point and Torlon is also replacing metal in transmission
metals in cars with lighter-weight plastics is a step-by-step engineering
process, not the overnight homerun of a Polimotor type of engine. But as CAFE
standards skyrocket, engineers will be looking for a bigger role for plastics.