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How are plastics made?
Most plastics are made using the hydrocarbons from natural resources such as oil and natural gas and also other
chemicals.
In technical terms plastics are produced by chemical bonding of monomers into polymers. The size and
structure of the polymer molecule determines the properties of the plastics material allowing huge variety and
versatility.
There are two basic types of plastics - thermoplastics and thermosets. Thermoplastics soften on heating and then
harden again when cooled. Thermosets never soften once they have been moulded.
The appeal of plastics
Advocates of the revolutionary approach, however, stress the advantages of plastics as a more radical
lightweight alternative to steel. Plastics are more than twice as light as aluminum and can be formed into a much
wider variety of shapes. Moreover, the equipment used to manufacture plastics costs much less than the heavy
stamping equipment required to make metal parts. These qualities have attracted automakers' interest since the
1960s.
Today the industry has incorporated plastics in a variety of uses; they form the interior components of most cars,
for example, as well as bumper covers and fenders. Manufacturers and designers have also used polymeric
composites--plastics reinforced with either glass or carbon fibers--in the bodies of race cars and some
commercially produced vehicles. In the 1980s, as automakers looked for new ways to reduce vehicle mass, many
in the industry began to investigate the use of polymeric composites to substitute for steel in automobile bodies.
Like aluminum, composite materials have their disadvantages. For one thing, they are more expensive than other
automotive materials. The plastic resin mixture costs between $1 and $10 per pound and glass fiber prices start
around $1 per pound. Glass fiber polymeric composites are price competitive with aluminum or steel only when
used in small quantities or in complex shapes that are prohibitively expensive to form from metal.
In addition, ordinary plastics are between one-thirtieth and one-sixtieth as stiff as steel, while reinforced plastics
are about one-fifteenth as stiff as steel. The traditional uses of plastics in automobile interiors capture the
advantages of light weight and ease of formation without requiring a high degree of stiffness. Unibodies,
however, have to be stiff to perform effectively. Structural panels composed of reinforced plastics must therefore
be much thicker than their metal counterparts, offsetting the reduced weight and raising costs even further.
Carbon fiber composites have drawn the industry's interest as an alternative to glass fiber composites because
they are stiffer. Panels composed of these materials can be made thinner--and thus lighter--than their glassreinforced counterparts. However, carbon fiber composites are prohibitively expensive: carbon fiber prices start
at $20 per pound and rise dramatically with increases in fiber strength and stiffness.
Polymer-based unibodies are also difficult to manufacture. Although bodies made of reinforced composites
would require only one-third as many parts as conventional metal bodies, these parts would have to be made to
fit together exactly--something that is beyond the state of assembly art today. Since plastic resin and carbon
fibers contract at different rates as they cool, the parts are bound to warp and shrink slightly in ways that vary
unpredictably from piece to piece. That's not unusual--steel changes shape as it cools, too--but materials like
steel can be bent and twisted into shape. For instance, assembly-line workers use wooden mallets and two-byfours to make sure steel car doors hang properly and seal when closed. Reinforced plastic components cannot be
deformed in this fashion--plastic will break sooner than bend--so there is no easy way to compensate for slight
imperfections in the way parts fit.
Finally, producing an affordable vehicle requires large-scale production, with volumes of at least 30,000 units
per year and possibly an order of magnitude higher. While nonstructural plastic components can easily be
manufactured on this scale, processing technologies for reinforced plastics are better suited to lot sizes of
hundreds or thousands rather than hundreds of thousands. The cheapest way to shift to mass production of
polymeric materials would be to speed up the process, making many more parts with the same equipment. But
the processes involved in manufacturing and shaping reinforced polymer-based materials are not particularly
amenable to this kind of straightforward scale-up.
The critical problem is that processing these kinds of plastics is inherently slow. The parts are formed by
preparing a mixture of ingredients and waiting for them to cool or react chemically. For parts the size of
automobile body panels, this process can take a minute or more. By comparison, steel parts can be stamped in
less than 10 seconds. It is hard to find ways to increase the rate of chemical reactions or the rate of heat transfer-if plastic cools too rapidly it becomes brittle, and if chemical reactions are sped up they become difficult to
control.
To make a large number of plastic parts, then, automakers would need to buy multiple machines and set up
parallel production lines--steps that would more than offset the capital advantage of plastic production and
increase administrative overhead. While parallel production lines may sound feasible in theory, they are very
difficult to coordinate in practice. As a result, automakers have tended to avoid processes that require more than
two parallel production lines.
Ultralite = Ultracostly
How much weight could a plastic unibody save, and at what cost? The most radical polymer system is the
Ultralite, a "concept car" based on carbon fiber composites that was developed by GM researchers given a
mandate to obtain the highest possible gas mileage. The car, which was built by hand, incorporated a variety of
weight- and fuel-saving technologies. Although the car was capable of getting more than 100 miles per gallon, it
cannot be considered a prototype for a mass-market vehicle: it did not contain the space or safety features most
consumers would consider essential and was never road- or crash-tested. Nevertheless, at 308 pounds, it
represents the lightest auto body yet built of polymeric materials.
Although the Ultralite weighs about the same as an aluminum space frame, it would cost significantly more to
produce in large volumes. At production volumes of 100,000, for instance, each Ultralite-style unibody would
cost about $6,400. This estimate is based on the assumption that carbon fiber prices will remain at about $20 per
pound. Proponents of polymeric materials have argued that the price of carbon fibers will decline as demand
rises. But even if the price of carbon fibers fell to $5 per pound--a trend we do not foresee, since the production
of carbon fibers is not necessarily amenable to economies of scale--the plastic unibody would still cost $3,500,
compared with $2,500 for a steel unibody and $2,800 for an aluminum space frame at comparable production
volumes. Moreover, at higher production volumes, the price of a steel or aluminum unibody will fall
considerably, while the price of a polymer-intensive unibody will fall much less, making it an even less
economically sound choice.
It is unlikely that the increase in fuel economy attributable to the body alone would make up for the higher cost
of a polymer-based body. At prices of $1.20 to $1.50 per gallon of gasoline, the Ultralite body would still cost
some $4,500 more than either a steel or an aluminum unibody over its life cycle. In fact, carbon fiber-reinforced
polymer-intensive bodies would still cost about $4,000 more than steel bodies even if gasoline prices rose to
$4.00 per gallon, as is the case in Europe.
What manufacturers are doing now
The automobile industry is also attempting to develop production techniques to put plastics on mass-produced
vehicles (notably GM's Saturn car lines), but even here the plastic components are not critical structural elements
of the vehicle. All Saturns, for instance, use plastic body panels to cover a steel space frame. Because they have
no structural role, the panels are made not of reinforced composites but of ordinary plastics, which can be
produced in quantities of hundreds of thousands. The choice of material is governed less by weight
considerations than by cosmetics: plastic panels give the vehicle its distinctive shape and resist dents and
scratches. In fact, the weight saving achieved by the use of plastic panels is at least partly offset by the need to
use more steel in structural components to maintain the expected level of performance.
Automakers have found that, with an aggressive effort, they can substitute polymers for steel in a handful of
major nontraditional applications, such as roofs, hoods, floor pans, and engine cradles, but many are also
discovering that the costs are too high and the weight savings unimpressive. GM has also experimented with
glass fiber composites on the body panels of its APV vans for a number of years but recently concluded that the
material is just too expensive. The company plans to return to using steel.
While they continue to experiment with glass fiber-reinforced polymers in niche-market vehicles--a wellestablished platform for innovation--automakers appear to have decided that these materials are not useful in
applications with production volumes over 80,000, because at these volumes the benefits do not justify the costs.
Moreover, it appears that the industry is already using plastics in most of the applications that are best suited to
the material's strengths. Further substitutions of plastics for steel will be much harder to accomplish, because
these are the uses that capitalize specifically on the properties of metals.
The Program for a New Generation of Vehicles, meanwhile, is investigating the potential uses of advanced
steels, plastics, and aluminum, as well as such exotic--and expensive--substances as magnesium and titanium. At
this early stage, researchers are trying to identify the technologies that could make up the platform for an
affordable advanced vehicle. They appear to be focusing their efforts on the concept of a hybrid diesel-electric
engine, for instance, and on aluminum as the dominant material for structural applications (although the vehicle
will undoubtedly incorporate a variety of advanced materials for other uses.) Whether or not the program
ultimately succeeds in developing a vehicle that is affordable--and there are rumblings that insiders believe it
won't--the effort will give the auto industry valuable experience with new materials and technologies.
Plastics vs Automobile Industry
Plastics’ use reaches record levels in automotive sector
A report published today shows a steady increase in the use of plastics by Europe’s car manufacturing industry
since the 1970s, rising to nearly two million tonnes today.
By volume, plastics are now the most widely specified material. However, plastics’ low weight means they
account for about 10 per cent of the total weight of a modern car.
The study, carried out by Mavel on behalf of the Association of Plastics Manufacturers in Europe (APME),
examines the use of plastics in cars over the last three decades in Europe with specific reference to France,
Germany and Italy.
The report shows that this increase in the use of plastics is particularly dramatic in certain types of cars. For
example, some of the cars surveyed registered a four-fold increase in their use of plastics between the 1970s and
1990s.
It is estimated that, on average, 100 kilograms of plastics replaces 200-300 kilograms of conventional material,
reducing fuel consumption by 750 litres over a life span of 150 000 kilometres.
Additional calculations across all cars suggest that this cuts oil consumption by 12 million tonnes and reduces
CO2 emissions by 30 million tonnes per year in Western Europe alone. Twelve million tonnes of oil equates to
approximately 10 per cent of passenger fuel consumption in Western Europe in 1996.
Plastics to build lighter cars
There are many examples in a modern car of weight savings made possible by plastics: plastics-made bumpers
are up to 10.4 kilograms lighter, engine covers 4.2 kilograms lighter and plastics fuel tanks five kilograms lighter
than those made of conventional materials. In turn, chassis, drive trains and transmission parts can all be made
lighter as a result of having to support a lower overall car weight.
These figures show the vital contribution plastics will make to help the automotive industry meet environmental
challenges. They confirm what was already highlighted in a study, ‘The car of the future, the future of the car’,
carried out by IPTS and published by the European Parliament, European Commission DGXII and the STOA
Panel in 1996. The authors report: "The automotive industry is approaching an era that may revolutionise its use
of materials. The major aim of the industry is to decrease the weight of the automobile in order to reduce fuel
consumption, and consequently emissions."
The industry’s move toward lighter vehicles means plastics consumption in the automotive sector will increase
dramatically. For example, a study carried out in Japan by MITI predicted that beyond 2000, use of plastics in
the average car could increase by 17 per cent from 115 kilograms (nine per cent of average car weight) in 1989
to 220 kilograms (26 per cent).
Plastics: reducing pollution and saving fossil fuels
Relatively little oil is needed to produce plastics. Western Europe consumed over 26 million tonnes of plastics in
1996, of which 7 per cent - nearly 2 million tonnes - were used in the manufacture of new cars during that year .
These plastics represent just 0.3 per cent of oil consumption - just one hundredth of the oil used as fuel by the
transport sector as a whole over the same period. Yet they are constantly helping to reduce the amount of fossil
fuel and resources consumed. These savings will rise as plastics’ consumption in the automotive industry
increases.
Commenting on the results of the study, Patrick Peuch, director at APME’s Technical and Environmental
Centre, said: "In today’s average car, there are already more than 1000 plastics parts of all sizes and shapes all
providing fine examples of the many benefits of plastics’ light weight, durability and versatility. With plastics
consumption set to rise steadily, cars in the next Millennium will be lighter, safer and even better designed for
people and the environment through their whole life cycle."
To obtain a free copy of the report, please contact APME’s communications Director (see below).
Plastics in Automotible Manufacture
Plastics in Automobile Manufacture - Environmentally Friendly and
Economical.
High-grade plastics are indispensable in the automobile industry today. Their use reduces the weight of vehicles
- and that saves fuel. And with greater stability, driving becomes safer. It is therefore essential to be able to
process plastics efficiently.
At BMW, they recognise the advantages of plastics. In their Landshut works in Germany, the cars are fitted with
components made of polyurethane. The components are manufactured on-site: Four compact tanks made by
H&S Anlagentechnik GmbH/Sulingen, Germany take care of storage, conditioning and transport of the plastic
components. The result is that production is always environmentally friendly; it is economical, and the products
are of a consistently high quality.
Additional advantages of polymers working in BMW's favour: plastics can be installed quickly and easily saving in commissioning time, more than 30% for plant start-up, and makes for a much tidier plant, clarifying
system design throughout the field. That's why BMW is sticking with Siemens in Germany.
The rubber and plastics industry, initially focused on automotive sub-contracting, has successfully diversified its
activities in other industries such as electronics, home-appliances, bottle extrusion for perfumes and cosmetics,
plastic furnishings and food packaging.
A full-fledged plastics technology sector has thus emerged in Sarthe, with some 90 companies employing 4,150
persons, accounting for 7% of the industrial workforce and achieving US$ 300 million sales.
These companies cover the full range of plastics technologies: injection, extrusion, thermoforming, calendering,
rotational moulding, compression, expansion... Leading national and international groups are present in Sarthe:
Demo Tableaux de Commande, ELF-Alphacan, Hutchinson, Framatome Connectors, Freudenberg, Inovac,
ARIES Industries, Raclet, Teleplastics Industries, AMS Europe...
Plastics technology industries benefit from the presence of some twenty local sub-contractors producing moulds,
patterns or prototypes. Education and training in the plastics industry runs from vocational high school diplomas
up to top-level engineering diplomas.
Car interiors
Plastics suppliers step up to the design table
It’s logical, it’s useful – and it may eventually spell doom to a whole range of plastic parts currently needed for
interior wiring.The development exemplifies a noteworthy trend in interior plastics, and it spells bad news for
any plastics supplier with a buggy-whip mindset. In the early 20th century, whip-makers, faced by the emerging
automobile industry, refused to recognize that technology was about to bypass them, and instead railed against
change and demanded protective legislation. Any plastics supplier finding itself in this position must adapt or
face extinction.Foam-in-place wiring could render some significant tooling and production methods obsolete. It
may also reduce the amount of manual labor associated with wiring harness manufacture. In addition, it may
reduce or eliminate several different kinds of automotive plastic products, including tape, tubes, straps, troughs
and grommets.Today’s interior systems integrators and their material suppliers can’t afford to be fearful of that
kind of change. They’ve learned that ignoring progress, or even just standing still waiting for orders to come in,
can turn them into road-kill.UT’s harness concept is just one of many that shows how plastics suppliers, Tier
One suppliers and the OEM customer are having to work collaboratively from the earliest stages of product
design. In UT’s case, it was the Tier One that brought together existing foam and a new application, but Tim
O’Brien, UT Automotive advanced engineering manager for instrument panels, says if the idea had come from a
materials supplier, it probably would have received the same fast-track treatment.
"I think we would have developed it just as aggressively with them, assuming they were willing to do a jointdisclosure kind of thing, so we could gain a leg up on our competitors," O’Brien says.
In fact, UT is currently evaluating polyurethane foams from Bayer, BASF and Dow for the application. But
today, plastics suppliers are expected to lead in the materials selection process, even helping automakers specify
for cast metal or hydroformed steel interior systems where the economics don’t favor an all-plastic solution.
Today, many molders are facing market trends that demand them to lower part costs, consider recyclability in
part design and reduce part weight. At the same time, they must also improve the soft look and feel of IP trim,
work in tandem with Design For Assembly (DFA) driven productivity strategies and increase product quality to
reduce buzz, squeak and rattle.
The resins help reduce part costs with no-paint, low-gloss, molded-in color surfaces. High-quality aesthetics and
UV stable parts provide consistent build quality.
In some applications, low-gloss resin savings can run upwards of 30% per part.
Doors
A PC/ABS resin has been specified for the 1997 Cadillac DeVille front door interior trim panel. This PC/ ABS
resin was chosen for this application due to its ability to take higher loads and higher heat than ABS or
polypropylene. This material advantage led to the specification of resin over competing materials. The PC/ABS
resin offers a unique balance of stiffness and ductility that meet these material requirements better than more
traditional materials such as ABS or polypropylene.
This door trim panel application exemplifies how engineering thermoplastic resins can contribute to not only the
aesthetics of a vehicle's interior, but also to the functionality that automotive designers now require from interior
components as they design vehicles to satisfy consumer demand for safety and comfort.
Molded-in hooks, which hold the trim panel tightly to the door itself to prevent rattles, were a functional feature
that required the higher performance characteristics that resin offered over competing materials. The door panel
is also made functional by the fact that it carries a speaker, has molded- in support for the arm rest, and is
delivered to the assembly plant with sound barrier material attached.
More and more, Tier One suppliers like Manchester Plastics look to their material suppliers for valuable
technical support throughout the product development cycle.
The one-piece thermoplastic Super Plug™ door module, a manufacturer of engineering thermoplastics, has made
its on-car debut with the launch of the 1997 General Motors minivans.
These minivans, sold as the Chevrolet Venture, the Pontiac Trans Sport, the Oldsmobile Silhouette, and in
Europe, the Opel/Vauxhall Sintra, sport a Super Plug designed specifically for this vehicle platform, but the
design can be translated to virtually any other production car or truck. In fact, a forthcoming midsize GM sedan,
to be sold as the Chevrolet Malibu and the Oldsmobile Cutlass, will soon launch with its own version of the
Super Plug door module.
Though vehicle owners may never actually see this new plastic component because it's positioned inside the
door, it will offer very good quality over conventional systems, along with serviceability that has already been
ranked "best in class." To consumers that means fewer squeaks and rattles from the door, and maybe even fewer
trips to the service department.
A traditional car door typically houses a complex array of parts that perform many functions vehicle owners take
for granted, such as wires and tracks for accommodating the windows and stereo speakers, components for the
door locking system, and the frame that provides structure to the door itself. The many intertwining parts make
the door an area in a car that is time-consuming and costly to assemble and often dissatisfies customers due to
squeaks and rattles and a high incidence of warranty claims.
The Super Plug integrates the function of many of these door components into a single thermoplastic part,
reducing the number of parts inside the door by up to 75%. With fewer parts inside the door, assembly time is
greatly reduced, and servicing the door system is made simpler. However, since the Super Plug's design will
differ from one vehicle platform to another, parts integration, assembly improvements and serviceability will
also differ from platform to platform, depending on the complexity of a vehicle's door system.
External applications
In automotive exterior applications is used resin, polybutylene terephthalate (PBT), polycarbonate because it's a
material solution that offers design and styling flexibility while meeting stringent OEN requirements: color and
property retention upon weathering precess abitily and mechanical and heat performance.
The air / fuel injection module
Thanks to new technical plastics, which withstand high temperatures and make optimum use of new processing
techniques, more and more of functional engine parts are being produced in composite materials. Solvay was
among the first in Europe to set up an industrial production line for thermoplastic parts using the fusible-core or
the vibration-welding injection technique. This allows the production of parts with complex shapes and
compliance with very severe specifications.
Driven by a fully integrated system approach, Solvay Automotive companies provide their customers with a
complete plastic module for the air intake function. Made using sophisticated technologies, this module is fully
equipped with air intake manifold, resonator, air filter, air ducts, fuel rail, injectors, etc.
This system has major advantages : better design, better engine output, lower weight and thermal conductivity,
fewer components, and less assembly work by the car maker. All of this amounts to lower costs and less material
waste.
The reasonator on the 1996 Dodge Neon is blow molded from NORYL GTX® resin manufactured by GE
Plastics. NORYL GTX® resin gives the application high heat and chemical resistance, and the blow molded
design helps reduce engine noise.
NORYL GTX resin is part of a family of engineering thermoplastics manufactured by GE Plastics that cover the
spectrum of performance requirements in the demanding environment of powertrain applications. Along with a
polyester polybutylene terephthalate resin and a polyetherimide resin, NORYL GTX resin fills a niche role in the
powertrain segment.
One recent example of NORYL GTX resin's performance is the resonator on the 1996 Dodge Neon. Both the 2.0
liter double overhead cam and single overhead cam engine options for Neon utilize a blow molded resonator.
The decision to specify this resin was based in part on its chemical resistance properties, hydrolytic and
dimensional stability characteristics and its ability to withstand temperatures from -40 to 300°F. GE Plastics
optimized the blend of polyphenylene oxide and polyamide resins to give a competitive performance advantage
over nylon resins. To meet the specification, the part was also required to pass automotive chemical resistance
tests for automotive fluids such as oil and antifreeze.
Of primary concern to underhood and powertrain engineers are high heat and chemical breakdown of component
materials. Resins are a cost effective material that is engineered to meet these specific challenges. With a heat
deflection temperature of 363°F, they can withstand the elevated temperatures that can be generated by a high
performance engine. Additionally, very good resistance against chemical breakdown from automotive fluids
makes resins a logical choice for applications such as engine resonators.
Another factor in the material specification were resins impressive processing capabilities versus nylon that
allow it to be injection molded or blow molded. Steere Enterprises of Tallmadge, Ohio, chose the blow molding
process because it was quicker to manufacture and less expensive than injection molding. Tooling cost savings
were approximately 15%, and 10 to 20% faster cycle times were achieved versus competitive materials in the
application. Blow molding provides the resonator application with important sound-absorbing properties that can
help minimize the engine noise that reaches the passenger compartment.
NORYL GTX resin was specified for the resonator application because it combines good mechanical properties
with overall system cost savings in automotive powertrain applications, and resins are a versatile material that is
engineered to perform in the demanding environment of powertrain applications.
NORYL GTX Resin Advantage:
Dimensional stability
Chemical resistance
Noise reduction
Low coefficient of thermal expansion
Weight savings
High heat resistance
Blow moldability
Surface appearance
The fuel management module
Plastic tanks feature major advantages over their metal counterparts. They are lighter, make optimal use of
available space, offer greater safety, better resistance to corrosion and are produced at a lower cost.
High-Density Polyethylene (HDPE) tanks, completely equipped with an electronic gauge, pump, filter, filling
tube and cap, are delivered by Solvay, ready to be assembled into the car body.
Furthermore among Solvay's plastics, Polyvinylidene Fluoride (PVDF) is the best barrier material: it withstands
high temperatures and corrosive acids and offers excellent barrier properties against fuels, additives and
alcohols. It is one of the materials which will be used for the new fuel lines in accordance with recent legislation,
in particular the Clean Air Act in the United States.
Under the hood
Small tanks (for windshield wiper fluid, for example) and battery cases are often made of polypropylene (PP).
Battery separators are made with PVC.
PVDF is one component in the electrodes of the latest generation of lithium batteries, which have substantially
increased the range of electric cars.
Cylinder-head covers, which must resist severe mechanical stresses, are made of polyarylamide or PPS
compounds, as are clutch master cylinders.