lexan polycarbonate for automotive forward lighting

Lexan Polycarbonate for Automotive Forward Lighting Blair T. Anthony, General Electric Plastics Europe, PB 117, 4600 AC, Bergen op Zoom, The Netherlands.

Abstract Through a mutual development effort between the Ford Motor Company USA and General Electric Plastics, the introduction in 1983 of the all plastic aerodynamic composite headlamp made from Lexan* polycarbonate is revolutionising the automotive forward lighting industry. European headlamp manufacturers have been working over the last several years with the automotive companies and GE Plastics Europe to develop a European design using plastic materials. Several European car models including Ford & Volvo are to be exported in 1985 to the US with plastic headlamps and reflectors made from Lexan polycarbonate. This paper discusses the many advantages and benefits which plastic headlamps offer both the manufacturer and the consumer. These advantages include excellent optical precision, superior damage resistance, unprecedented styling, improved aerodynamics and light weight.

Introduction

Forward lighting for automobiles has undergone many changes since it was introduced on vehicles in the early 1900's. The desire to increase the usability of cars at night and during inclement weather where visibility is imperative, spurred the beginning of automotive forward lighting development.

During the early 1900's lighting for vehicles began by use of mounted oil lamps on automobiles. Soon thereafter, the oil lamp was replaced by the acetylene gaslight which gave better light output with easier serviceability.

*Lexan is a registered trademark of the General Electric Company

At the beginning of the 1920's the use of the electric light found its way onto the automobile. This was the first major breakthrough in automotive forward lighting, because of the elimination of regular service and increased design freedom. As automobiles increased in number and roads became more con- gested in the 1930's, the first lights were produced using lenses to focus the light where it was needed in order to maxi- mise driver visibility and limit the blinding of other drivers by stray light. By 1939 the first sealed beam headlamp was introduced in the US and this technology is still used today. How- ever, during the 1970's, with the in- creasing prices of fuel and worldwide desire to increase fuel economy, there

was a demand to minise vehicle weight and increase the application of aerodynamics in the automotive industry. This would involve new uses of plastics to replace metal and glass.

A significant step toward the realis- ation of an all plastic headlamp was made in 1979 by General Electric Miniature Lamp Division who began production of an all plastic sealed beam type headlamp for the US market. A diagram of a sealed beam headlamp is shown in figure 1. This halogen headlamp has a reflector and lens entirely constructed in Lexan polycarbonate with the two halves welded together. This lamp which fully satisfies SAE requirements has a weight of less than ~J of the existing glass unit. (180 vs 570

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Fig. 1 Sealed Beam Headlight Configuration

MATERIALS & DESIGN Vol. 6 DECEMBER 1985 293

grams). In addition, the lens has better optical performance since plastic in- jection moulding yields more accurate and reproducable optics enabling an accurate beam control with improved light output. The high impact strength of these Lexan lenses, more than 100 times stronger than glass lenses, is a major advantage over the glass headlamps which are frequently broken in use from stone impact.

This first generation plastic headlamp has been proven in Lexan polycarbonate since it was introduced in September 1979 on the Ford Lincoln Continental and provides a strong data base to use Lexan as a glass replacement in future forward automotive lighting. More importantly, since this first generation plastic headlight was basically a copy of the glass unit, it reduced vehicle weight but it did not take into account the many further benefits possible with the utilisation of plastics. Today, the emphasis is to extend this plastic headlamp by intro- ducing a new generation of plastic headlamps with aerodynamic styling providing improved performance over glass. The ability to mould close tol- erance precision optics, far superior to glass, enables the plastic lens to be inclined at virtually any angle. This has

been shown by car manufacturers to reduce drag and to harmonise styling. Moreover, during the early 1980's, headlarnp manufacturers became fam- iliar with the other advantages of using plastic instead of glass, such as better optics, reproducability of the prism and high impact resistance in addition to lighter weight. It was also understood and accepted that a protective coating had to be applied to protect the plastic lens outer surface against aggressive automotive fluids, abrasion and severe outdoor weathering in order to provide a headlarnp that could survive the life of the vehicle.

In Europe, headlamps have developed in a different way than in the US. For example European headlamps are much larger and complex giving more light output and therefore run much hotter. As can be seen in Figure 2, they are at present made with glass lenses, housings or extenders made in thermoplastics, metal reflectors and utilise replaceable bulbs. Furthermore, the much closer control of low beam cut-off requirements demands a radically different construction and styling. Also there is a demand for more light to reach the side of the road due to the higher number of pedestrians and cyclists. These requirements, together with the

Groupe de Travail de Bruxelles (GTB) legislation not as yet allowing plastic headlight lenses in Europe, and the heavy investment European headlarnp manufacturers have in glass processing equipment, provide both an opportun- ity and a constraint for the adoption of plastic lens materials in Europe.

Japanese regulations allow the use of plastic for headlamp lenses and in 1982 Toyota introduced into the Japanese market plastic headlamps on the Sprin- ter. This headlight has been very successful and the lens is manufactured of Lexan polycarbonate and is coated with an ultraviolet curable acrylic coating from Mitsubishi, Japan. How- ever, the Mitsubishi coating cannot be used as a coating for plastic headlamps in the US because it does not meet the current Federal Motor Vehicle Safety Standards 108 regulations regarding abrasion resistance, chemical resistance and Florida weathering. Although acrylic coatings are generally very weatherable, they are much softer than those of silicone and also have poor chemical resistance. Even with these limitations, the plastic Toyota headlamp is a huge success in Japan and other Japanese manufacturers are following Toyota's lead. A picture of the Toyota Sprinter headlight is shown in

Fig. 2 European Conventional Headlamp Design

294 MATERIALS & DESIGN Vol. 6 DECEMBER 1985

Fig. 3 Toyota Sprinter Plastic Headlamp

figure 3. In the autumn of 1983, after govern-

mental regulation changes, an all plastic aerodynamic composite headlamp moulded from Lexan polycarbonate was introduced in the US by the Ford Motor Company on the 1984 Lincoln Continental Mark VII. This headlamp is shown in Figure 4.

A common aim is shared between the US and Europe, to provide better, safer and more economical headlamps. It is hoped that through this new generation of plastic headlamp, the best of both countries' headlight technology will be combined, providing international ac- ceptance and harmonisation of an all plastic composite headlamp design with a replaceable bulb.

US Regulation change allowing plastic headlamps

On July 1, 1983 the US Department of Transportation's National Highway Traffic Safety Administration (NHSTA) amended the Federal Motor Vehicle Safety Standards FMVSS 108, via Docket No. 81-11; Notice 3, (1) to allow an all plastic aerodynamic composite headlamp. The amendment is based upon a petition from the Ford Motor Company working closely with General Electric Plastics and is pri- marily directed towards a non-fully sealed all plastic composite beadlamp design. This notice completed rule- making initiated by the NHTSA pub- lication of a notice of proposed rule- making on new beadlighting systems on January 17, 1983 (48 FR 1992).

The All Plastic Aerodynamic Com- posite Headlamp The primary problem that needed to be overcome in order to achieve an all

plastic aerodynamic composite headlamp with a replaceable bulb, was to find a way to produce headlamps that retain the positive features of today's sealed beam lamps while providing ready replacement bulbs for those that may bum out during service. From Ford emerged a headlamp design simi- lar to the European one but using plastic and an inexpensive standardised replaceable bulb. Ford engineers have

developed a composite headlamp that combines the advantages of sealed beam technology with the design flexi- bility and ease of bulb replacement developed by European technology. The basic design of Ford's Composite Headlamp ~2) is illustrated in Figure 5. The diagram shows the adjusting screws located in the headlamp housing for horizontal and vertical adjustment of the aim of the lamp. The lamp has also been designed to accommodate both mechanical and optical aiming tools. The simplicity of the design is to be compared with the sealed beam configuration in Figure 1. The composite headlamp consists of:

a clear plastic contoured lens bonded to the reflector forming an integral assembly. a plastic directly metallised reflector which includes a socket to accept the standardised bulb. a replaceable bulb.

Materials Lens

Since it is the aim of the new composite headlamp, under normal service opera- tion, to last the life of the vehicle, the contoured lens is being manufactured out of a tough, high impact resistant transparent plastic. Ford's choice was a

Fig. 4 1984 Ford Lincoln Continental Mark VII Plastic Composite Headlamp


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Fig. 5 Ford Aerodynamic Composite Headlamp Design

high temperature thermoplastic Lexan LS2* polycarbonate resin which provides more than 100 times the resistance to breakage than glass lenses while giving precision optics and the ability to mould to closer tolerances with improved light output compared to glass. The Lexan lens is provided with further protection against abrasion, severe outdoor weathering and automotive fluids by coating the outer surface with a Silicone Hardcoat system SHP 300/SHC 3000 developed especially for Lexan polycarbonate by General Electric. This lens is designed to maintain the optical performance of the lamp over the lifetime of the vehicle.

Reflector Lexan polycarbonate resin was also chosen for the reflector because of its high temperature resistance, dimensional stability and its non-corrosive high durability qualities. Also Lexan can be directly metallised with alu- minium followed by a clear coat to prevent environmental degradation of photometrics during its service life. The moulded Lexan reflector includes a standardised rear aperture and socket to accept the standarised replaceable bulb. Other engineering thermoplastics being used as metallised reflector materials are Xenoy**, Valox*** Ultem**** manufactured by General Electric Plas- tics.

*Lexan LS2 is a special type of Lexan polycarbonate developed by General Electric Plastics for optical lens applications.

**Xenoy is an unreinforced composite polymer material developed for the automotive industry offering a combination of mechanical tough- ness, chemical resistance and dimensional stability. ***Valox is a modified thermoplastic polyester resin providing properties such as chemical resistance, mechanical and thermal performance, electrical insulation and dimensional stability. ****Ultem is a polyetherimide resin providing excellent chemical resistance and excellent dimensional stability at elevated temperatures, t4}

Replaceable Bulb The standardised bulb has been designed to permit manufacturing to tolerances that accurately control the location of the bulb filament relative to the mounting base. The bulb base incorporates a silicone 'O ' ring seal which mates with a precisely controlled surface in the reflector. The use of high performance engineering thermoplastic Lexan polycarbonate resin for the lens and the reflector provides a corrosion resistant and highly durable headlamp assembly that provides long service life without the concerns of photometric degradation from corrosion as in metal reflectors. The photometric performance of the composite headlamp is equivalent to today's sealed beam headlamps.

By addition of the feature of internal sealing by means of an 'O ' ring between the bulb and the socket, the European concept of the replaceable bulb is

obtained while eliminating the requirements of venting. This needs air ex- change through a controlled path to the outside atmosphere, as well as some external method of protecting the bulb from the environment by various means which include complicated housings.

Assembly The lens and the reflector can be joined together by either the use of adhesives or vibration welding. The choice is mainly dependent on the shape and design of the headlamp lens and reflector. Tests have shown that the pressure build-up inside the sealed headlamp cavity due to typical operating conditions is approximately 0 . 3 bar. However, due to the excellent strength of Lexan, pressures of up to 30 bar can be contained within the lamp body.

The bulb is inserted into the reflector assembly via a bayonet mounting because it provides a positive "one-way only" system. A single oil impregnated silicone 'O ' ring provides the seal for the bulb. The time required to replace one of the new standardised bulbs is about one-fifth that required to replace a sealed beam unit. The procedure for inserting the bulb from the rear of the lamp is shown in Figure 6. The bulb is installed into the reflector with a straight push-in motion, only achieved after proper orientation of the respective keyways. The locking cap is rotated and this secures the bulb base to the reflector. The integral plastic sleeve protects the terminals from mechanical damage.

Other Plastic Composite Headlamp Advantages

Improved Aerodynamics It has been found that the headlamps can reduce the aerodynamic drag of the vehicle by as much as 5% via the flush mounted contoured headlamp design.

Fig. 6 Replaceable Bulb Assembly

296 MATERIALS & DESIGN VoI. 6 DECEMBER 1985

Just by a change of headlamp designs, the contribution to vehicle fuel economy could be significant. Upto half a billion dollars could be saved in annual fuel costs in the US alone.

Resistance to Breakage Currently about 10.8 million broken glass headlamps are replaced each year in the US. Since plastic headlamps made from Lexan are 100 times more resistant to breakage than glass lenses, it is estimated that the number of headlamps would be reduced to only 0.7 million if all vehicles were equipped with headlamps using Lexan polycarbonate lenses. Figure 7 illustrates the significant impact resistance advantage Lexan has over glass and acrylic. The excellent impact resistance of Lexan headlamps is shown in Figure 8 - a 1984 Ford Lincoln Continental Mark VII which has been in a severe front end collision. The front end of the vehicle is significantly damaged but the Lexan aerodynamic headlamp is undamaged.

Even though it is recognised that acrylic is not a viable candidate for use as a plastic lens in forward lighting, due to its insufficient impact resistance and low heat resistance, it is used in this paper as a comparison with polycarbonate, because of its well known properties and worldwide uses in less critical transparent applications.

For reference, wherever "Coated Lexan" is mentioned in a figure, it is referring to Lexan LS2 coated with SHP 300 and SHC 3000.

High Heat Resistance Lexan has a Heat Distortion Temper- ature Under Load (DTUL) of 137°C. Acrylic has a D T U L of only 85°C which is unacceptably low for forward lighting applications; the D T U L of

Lexan is more than sufficient for most applications.

Self Cleaning Most of the headlamps today are recessed in a cavity standing in the vertical position. This creates a potential problem of dirt and snow being trapped in front of the headlight reducing its effective light output. An advantage of contoured flush mounted aerodynamic lenses is that they tend to be self cleaning because of the "wip- ing" action of the air and water flowing over the lens during inclement weather. This helps to reduce the incidence of

dirty headlamps and therefore results in an increase in driving safety.

Serviceability The servicability of a headlamp basically requires three main functions. These are: the availability of a replacement in the case of breakage or burn out, the ease of installation and the need to realm the lamp following replacement. Due to the fact that the majority of failures of the new composite plastic headlamp will be from bulb burn out and not from breakage, availability of replacement bulbs becomes the primary concern. Since the bulb is sinai-

Fig. 8 80 KPH Front End Collision of Lexan Composite Headlamp

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ler, lighter and has a low design cost than today's replaceable sealed beam headlamps, it can be more efficiently and conveniently stocked by service stations, department stores and other typical sources of replacements. The time required to replace one of the new standardised bulbs is about one- fifth that required to replace a sealed beam headlamp unit, resulting in savings in service operations. Accur- ate control of the design tolerances of the replaceable bulb and its location in the reflector, means that replacement of the bulb will not necessitate reaiming- which gives another important advantage.

time that will demonstrate the lamps ability to withstand US driving conditions for the service life of the vehicle. These tests include photometry, abrasion, vibration, chemical resistance, corrosion, dust, temperature cycling and internal heat, humidity, impact and Florida weathering. Details of these tests in NHTSH FMVSS No. 108 docket No. 81-11; Notice 3 effective on July 1, 1983.

The behaviour of Lexan polycarbonate resin, coated with General Electric SHP 300 modified acrylic primer and SHC 3000 polysiloxane hardeoat, has been extensively studied during both laboratory and outdoor

weathering. Listed in Table II are typical product performance data of SHP 300/SHC 3000 coated Lexan polyearbonate. Taber abrasiod 6) is a function of surface hardness and is measured by the change in haze of the part before and after the grinding test. For reference, a measured haze of more than 5% is required to be noticeable to the normal human eye. The 65 °C water immersion test ~7) demonstrates the excellent adhesion that the coating has to the Lexan surface. Most other coatings will last no longer than 100 hours in this severe test. QUV weathering is recognised as the most severe laboratory accelerated weathering test for plastics,

Protective Coating for Property Retension Since lens materials are changing from glass, which is esentiaUy unaffected by natural weathering, to a plastic material, a coating must be applied to maintain the beneficial properties of the plastic material during prolonged exposure to outdoor weathering. Lexan polycarbonate resin with its impact Strength, temperature resistance, lightweight and excellent optics appear to be the ideal plastic candidate as a replacement for glass. However, since car manufacturers and consumers expect an automobile to last 10 years it is important to provide the optimum performance from the components. To ensure that a Lexan composite headlamp will satisfy these demands, a transparent protective coating system has been developed and patented by General Electric's Corporate Research and Development Centre for protecting the exterior surface of the lens. During the 5 years of continuous research and development, this advanced silicone hardcoat, SHC 3000, and primer, SHP 300, were developed especially for Lexan, which further improves and maintains Lexan's already good weather- ability, chemical resistance and abrasion resistance during severe outdoor weathering/5) In Table I is listed some of the more important features and benefits obtained by using SHP 300 and SHC 3000 - a protective transparent coating for Lexan polycarbonate.

To accept Lexan polycarbonate coated with SHP 300 and SHC 3000 for forward headlamp lenses, a number of tests have been developed in order to preserve today's levels of sealed beam headlamp performance. These performance speeifieations have been designed to subject a headlamp to severe operating conditions and for periods of

Table I SHP 300 /SHC 3000 Coated Lexan Product Features and Benefits

Products Features Potential Benefits

Ultraviolet Yellowing Resistance

Abrasion and Marring Resistance High Heat Resistance Impact Resistance

Scratch Resistance

Clarity

Solvent/Chemical Resistance

Weatherable Coated Parts

Durable Coated Parts

Easy Handling of Coated Parts

Excellent Optical Quality Parts

End Use Versatility

Table II Typical Product Data of SHP 300/SHC 3000 Cured Film on Lexan LS2

Taber Abrasion (6) Water Immersion 65°C (7) QUV Weathering (8) Chemical Resistance (9)

Delta % Haze 2 - 8 500+ Hours Adhesion 2000+ Hours Adhesion Resistant to all normal fluids found in the automotive environment. (ie. Petrol, brake fluid, oil)

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298 MATERIALS & DESIGN VoI. 6 DECEMBER 1985

simulating outdoor Florida weathering. The test subjects samples to intense Ultraviolet light as well as humidity and temperature cycling. Although it is difficult to make a correlation between QUV weatherin~ s) and Florida weathering, the QUV is an excellent and reproduceable method of ranking the performance of coated and uncoated plastic materials. It was not until the development of SHP 300/SHC 3000 coated Lexan polycarbonate that a coated plastic could survive more than 1000 hours scribed adhesion on the QUV "weathering".

Illustrated in Figure 9, is a comparison between the abrasion resistance of Lexan coated with SHP 300 and SHC 3000, coated and uncoated acrylic and glass. It can be seen that although SHP 300/SHC 3000 coated Lexan is not quite as abrasion resistant as glass, it has equal abrasion resistance as coated acrylic and very much more abrasion resistance than uncoated acrylic. The high Ultra Violet stability that S l ip 300/SHC 3000 provides Lexan is evident in Figure 10. For reference, a yellowness index of 4 is barely visible to the normal human eye.

Florida WeatheringCl°~ of SHP 300/ SHC 3000 Coated Lexan Poly- carbonate

Exposure of materials to the elements in southern Florida is recognised as a useful way to rank the outdoor performance of materials. The southern Florida climate provides a unique combination of conditions that accel-. orate natural weathering deterioration of plastics. These conditions include intense ultra violet radiation, high humidity, night-time condensation, high temperatures and wide temperature fluctuations, airborne contaminants and pollution. Of these, it is generally agreed upon that exposure to UV radiation and water are the primary weathering stresses. While Florida weathering is an excellent means of evaluating and ranking materials, it cannot be accurately used to predict actual life in an end use situation. Florida weathering results should be interpreted and used only in the context of the exposure conditions used during the test period.

Many industries have incorporated accelerated weathering in Florida into their performance standard requirements. SAE J576c, 1970, recommen- ded practice for "Plastic Materials for Use in Optical Parts, Such as Lenses and Reflectors of Motor Vehicle Light- ing Devices" specifies three years of south Florida exposure at an angle of

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45 degrees south facing, for materials that are "exposed to direct sunlight as installed on the vehicle." NHSTA has incorporated this 3 year Florida weathering requirement into FMVSS 108.

Illustrated in Figures 10 to 14 are the changes in yellowness index, light transmission, haze and impact strength after Florida weathering of LEXAN coated with SHP 300 and SHC 3000.

Even after 3 years Florida Weather- ing it is seen that all of the initial properties of Lexan polycarbonate are maintained by using SHP 300/SHC 3000 as a protective coating. There is no blistering or peeling of the coating, no colour change of the coating or Lexan, no loss in light transmission, little haze formation and no change in impact strength or chemical resistance. Lexan polycarbonate resin protected with SHP 300/SHC 3000 has many design and performance benefits when compared with glass and it is strongly believed that the future technology of forward lighting will certainly take advantage of engineering thermoplastics.

European produced Plastie Forward Lighting Lenses In July 1984 through the combined efforts of Hella, Germany and General Electric Plastics Europe, the first production of a plastic forward lens was started by Hella for the Federal Ford Merkur XR 4Ti. This lens is made of Lexan polycarbonate coated with SHP 300 and SHC 3000, and is used as the front position lamp lens. A picture of this lighting device is shown in Figure 15.

Expected Plastic Aerodynamic Head- lamp Growth Plastic aerodynamic headlamps are revolutionising the automotive forward lighting industry. In the near future it is expected that every headlamp manufacturer in the world will be producing plastic headlamps and that nearly every automobile manufacturer will have car models with plastic aerodynamic headlamps. It is expected that the annual production of plastic composite aerodynamic headlamps will soar to 20 million by 1990 in the US.

Since plastic headlamp lenses currently are not legal in Europe and most likely legislation will not allow plastic lenses until sometime in 1986, the growth of plastic headlamps will be slower in Europe since all current production must be exported to the US. However, by 1990 it is expected that European production of plastic aerodynamic headlamps will equal that of US production. Illustrated in Fig. 16


Fig. 15 First European Produced Plastic Forward Lighting Lens

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is how it is believed that the European and US plastic headlamp production will grow over the next 5 years. Taken into account is the assumption that the GTB will change legislation in 1986 which will allow plastic headlamp lenses in Europe.

Coneluslon Lexan polycarbonate resin has been used successfully for exterior automotive lighting since 1971 in lenses and housings for all types of exterior lighting applictions. These range over small licence plates to large cornering lamps and integrated stop, turn and tail lamps. Because nearly 11 million headlamps

are replaced annually in the US alone, there is pressure to change the lens material from glass to impact resistant plastic. It is estimated that about 90% of this stone damage could be thereby avoided. In 1979 the first plastic sealed beam headlamp was successfully introduced by Ford on the 1980 Lincoln Continental using Lexan polycarbonate resin for the lens and reflector.

The change in US federal headlamp standards which now permits contoured plastic headlamp lens surfaces and a standardised replaceable bulb, enabled the Ford Motor Company, in the autumn of 1983, to introduce a plastic composite headlamp on the 1984 Lin-

coin Continental Mark VII. Both the lens and the reflector are moulded with General Electric's Lexan polycarbonate and the lens is further protected against weathering, abrasion and chem- icals by an advanced Silicone Hard- coating system, SHP 300/SHC 3000, developed by General Electric's Cor- porate Research and Development Centre especially for Lexan.

This new aerodynamic composite headlamp design which takes advantage of both US and European headlamp technologies is being expanded by Ford with Lexan lenses in the 1985 Mark VII again, as well as on the Merkur XR 41i and Escort models. The Lexan polycarbonate lenses are 100 times stronger than conventional glass lenses and replacement of the standarised bulb is easier and less expensive than replacing a conventional sealed beam headlamp, requiring only about one-fifth the time and two- thirds the cost. A further advantage is the ability to mould Lexan into complex shapes that are impossible in glass, making possible the contoured design of the new plastic composite headlamp which improves the aerodynamic ef- ficiency of the vehicle, reducing air drag by as much as 5%. Another benefit is that Lexan lenses weigh less than half as much as comparable glass lenses while optically the plastic lenses are 30% better than glass as measured by light transmission. Japanese legislation allows plastic headlamp lenses in Japan and in 1982 Toyota introduced a plastic headlamp using Lexan polycarbonate as the lens material. European interest in the all plastic headlamp has been growing since the early 1980's, even though plastic headlamp lenses are not as yet legal in Europe (it is expected that a regulation change allowing plastic headlamp lenses in Europe will be passed by early 1986). However, the European headlamp manufacturers have been working con- tinuously over the last several years with the automotive companies and General Electric Plastics Europe to develop a European headlamp design utilising plastic materials. Because of these joint programs there will be several European car models, including Volvo and Ford, exported to the US in 1985 with plastic headlamps made from Lexan polycarbonate and protected with the SHP 300 and SHC 3000 coating system.

The introduction of the plastic headlamp made from Lexan polycarbonate is revolutionising the automotive forward lighting industry worldwide. The advantages of excellent optical preci-


sion, superior damage resistance, unprecedented styling, lightweight and low-cost maintenance provide the manufacturer and the consumer the headlamp performance expected from glass with many added benefits that glass is unable to fulfil. By 1990, it is expected that the production of plastic headlamps will exceed 40 million per year and that every headlamp manufacturer and automobile producer in the world will be utilising and profiting from this new and exciting technology made possible by engineering thermoplastics.

References

I. For further information contact: Jere Medlin, Office of Vehicle Safety Stan- dards, NHTSA, 400 Seventh Street, S.W., Washington D.C. 20590 United States (202-426-2720).

2. Design of Ford Motor Company North American Automotive Operations.

3. US Patents 4,278,804 4,247,475, 4,260,719, 4,263,222 and 4,373,060.

4. More information regarding Lexan LS2 polycarbonate, Xenoy, Valox and Ultem thermoplastics can be obtained from: In Europe General Electric Plastics B.V., Plasficslaan 1, 4600 AC Bergen op Zoom, The Netherlands, Telephone: 01640-32911 Telex: 78421

In the United States Plastics Group, General Electric Company, One Plastics Avenue, Pittsfield, MA 01201, USA. Telephone: 413-494-4601 Telex: 926430

5. More information regarding SHP 300 and SHC 3000 can be obtained by contacting the General Electric locations listed in footnote 4 or by cOntacting the author (Telephone 01640-32051).

6. Abrasion tests using a Teledyne Abraser model 503 standard Abrasion Tester manufactured by Telebyne Taber North Tonawanda Ny, USA, with 500 gram load on each wheel. Haze measured per ASTM-D1003-6L on a Gardner model XL-835 colorimeter.

7. Water immersion in tap water at 65°C. Samples checked daily for scribed tape adhesion. The adhesion was tested by the cross-hatch method (ASTM 3359). The coating was cut with a lattice cutting device (Erichsen, Germany) and tested with an adhesion tape (Scotch 710, USA). Only 100% retention of adhesion after the third fresh tape pull was con- sidered as passing.

8. QUV weathering data on QUV instru- ment manufactured by Q Panel Corpor- ation, Cleveland, Ohio, USA. Weather- ing cycle is 8 hours UV fight at 70°C followed by 4 hours dark condensing humidity at 50°C. Samples checked each 100 hours for scribed tape adhesion as per method described in 7.

9. Saturated cotton ball placed on coated substrate followed by a watch glass to prevent evaporation of solvent being tested. After 30 minutes exposure, coated substrate is checked for any change in properties.

10. Florida testing done at: South Florida Test Service Inc., 9200 N.W. 58th Street, Miami, Florida 33178 USA. Telephone: 305-592-3170 Telex: 25-4328

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The Adhesives Handbook is a reference book which covers the wide variety of adhesive materials in a practical manner which saves valuable design office time. It enables readers to identify bonding problems, select the appropriate adhesive and trace its source. Furthermore, the properties, processing characteristics and applications of all commercially available adhesives

are clearly tabulated in an easy to use format.

The extensive Adhesive Product Directory of the third edition has now been revised and updated to provide the most comprehensive and reliable source of information on adhesives available in

Europe today.

Hardcover 384pages 246x 189rnm Illustrated 0408013567 1984, revised 1985 £45.00

El DL-I

Order from your local bookseller, or in case of difficulty from

BUTTERWORTHS, BOROUGH GREEN, SEVENOAKS, KENT, TN15 8PH


lexan polycarbonate for automotive forward lighting

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