(photo: [59]) From Rubber Tires to Plastic Cars · 2010. 11. 28. · more as of the 1930s. The DKW/Auto Union in Zschopau/Zwickau, Germany, used compression molded phenoplastic components

56

1 00 Y EARS O F KUNST S TOFFE

© Carl Hanser Verlag, Munich Kunststoffe international 5/2010

GÜNTER LATTERMANN

This article provides an overview ofsynthetic polymer-based materialsin the automotive industry. Some 71

years ago, a similar retrospective of theInternational Automobile and Motorcy-cle Exhibition held in Berlin, Germany, in1936 was published in the journal Kunst-stoffe back then with the title “Kunststoffeim deutschen Kraftfahrbau” (“PolymerMaterials in the German Automotive In-dustry”) [1].

Tires

The mechanical engineer Karl Benz builtthe first motor vehicle with an internal-

combustion engine [2]. The applicationfor a patent that was filed in spring of1886 was granted at the end of the year.The first public test drive of his “horse-less carriage” took place in the summerof 1886. The left Title photo shows Karl Benzsteering this first – three-wheeled – mo-torcar. It had one major advantage overits competitor, the four-wheeled, wood-en “motorized carriage” built by GottliebDaimler: its wheels were not iron-mount-ed, but were rather equipped with hardrubber tires. At this time, hard rubbermeant basically natural rubber to whicha large amount of sulfur had been added,and which received its final characteris-tics, i.e. elastic properties, during heating.This process is known as “vulcanizing”.Astire material, hard rubber was first usedfor bicycles by Thomas Hancock in 1852[3], but had higher rolling resistance andpoorer riding characteristics than the in-

flatable rubber tires introduced later(John Boyd Dunlop, 1888). These weremounted for the first time on an automo-bile, a Peugeot Éclair, in 1895 by thebrothers Edouard and André Michelinfrom Clermont-Ferrand [4] – the famous“pneus” (from the Greek “pneuma” =wind, breath) became the standard in theautomotive industry since then.

The first pneumatic tires made of ful-ly synthetic methyl rubber were intro-duced in 1910 by the ContinentalCaoutchouc Compagnie in Hanover,Germany, and even installed on the Ger-man Emperor’s car [5].

Windows

However, other polymer materials werealso of interest for the still very youngautomotive industry. For instance, withthe increasingly “fast” vehicles, it became

From Rubber Tires to Plastic CarsAutomobile. Polymer materials have been used in automobiles since the very

beginning. The first motor vehicles ran on hard rubber tires. From here it took a

long time to reach the level of use seen in today’s vehicles. This article looks back

over the first 50 years, but also casts a glance at current developments and closes

with the outlook for future use.

Karl Benz steering his three-wheeled patented motorcarriage no. 1 in 1886 (photo: [59])

Mercedes-Benz SLRMcLaren made usingcarbon fiber-reinforcedplastic, 2003 (photo:Wikipedia)

Translated from Kunststoffe 5/2010, pp. 104–110Article as PDF-File at www.kunststoffe-international.com; Document Number: PE110402

56-61_PE110402_PE5 07.05.2010 11:08 Uhr Seite 56

W 2010 Carl Hanser Verlag, Munich, Germany www.kunststoffe-international.com/archive Not for use in internet or intranet sites. Not for electronic distribution

57

>


Kunststoffe international 5/2010

necessary between 1886 and 1920 to in-stall “windshields” on the more or lessopen motor carriages. On “Landaulets”,at least the passenger compartment wasequipped with a folding roof. Fully en-closed sedans such as the RenaultVoiturette type B dating from 1889 were,from the very beginning, built to providebetter protection from the weather for theoccupants. This required a minimum offour transparent windows, but produc-tion of flat glass was a major problem fora long time. The still largely manual tech-niques used to manufacture glass for mir-rors yielded flat glass with highly distort-ing optical characteristics if it did not un-dergo very expensive polishing. It was on-ly from 1913 on [6] (in Germany, from1922 on [7]) that an improved, but opti-cally still “uneven”so-called “drawn glass”was produced industrially [8]. However,it had only a maximum thickness of upto 4 mm, i.e. was relatively thin, easilybroken and sensitive to loose chippings

on the road as well as other impact. Thislead to the search for alternatives fromvery early on.

Only after production of cellulose ac-etate began in Germany at Rheinisch-Westfälische Sprengstoff AG in Troisdorf,Germany, in 1909 under the brand nameCellon on the basis of the patents issuedto Arthur Eichengrün were “flexible Cel-lon panes” subsequently used in the“summer top” of a Daimler body in 1912as “unbreakable” glass [9]. However, theCellon windows were not successful on alonger term, because they were sensitiveto moisture and not resistant to defor-mation over time. Nevertheless, plasticwindows remained a subject of discus-sion, especially after 1935 when the new“organic glass” called Plexiglas started tobe produced industrially by Röhm undHaas AG in Darmstadt, Germany. Themanufacturing process with its easy ther-moformability and the optical character-istics were so successful that, starting in

Fig. 1. Opel Super 6 streamlined sports car, windows equipped with Plexiglas, 1937 (photo: [10])

Fig. 2. Messerschmitt Cabin Scooter with Plexiglas cockpit (photo: [12])

1937, especially spherical shapes weremanufactured for use in automotive ap-plications. These can be seen, for in-stance, in the domed windows of astreamlined sports car from Opel (Fig. 1)or those of a streamlined bus [10] andthe sunroof of an Opel Olympia car from1939 [1]. Unfortunately, even the Plexi-glas windows proved successful in only afew cases of automotive use because ofinsufficient material hardness andscratch resistance – quite in contrast toits large-scale use in airplane canopies[11], where impact from loose chippingswas of no concern. Perhaps the best-known automotive-related application,derived directly from airplane canopies,is the use of Plexiglas cockpits for theMesserschmitt Cabin Scooter datingfrom 1953 (Fig. 2) [12].

Nevertheless, the windows of mosthigh-volume production vehicles are stillnot plastic today, even though thescratch resistance of the now-favoredpolycarbonate – and thus also the price– has improved through use of variouscoating techniques. Polycarbonate has,however, been used as the material forlarge roofs in experimental versions ofsports cars, where low weight is a majorissue. Moreover, in the Rinspeed ZaZenexperimental car based on the PorscheCarrera 911, the polycarbonate roofcan, at the push of a button, be turnedmilky to provide protection from the sun[13, 14].

The other alternative for automobilewindows – safety glass – has found muchgreater success. Starting in 1927, celluloseacetate was sandwiched between twopanes of glass. The trail-blazing applica-tion of this laminated safety glass camein 1927, with its use in the Ford Model A(Fig. 3) [15 to 17]. Today, safety glass is em-ployed in every car, albeit with differentpolymers than as the intermediate layer(e.g. polyvinylbutyral).

Electrical Equipment

All electrical equipment (electric motors,capacitors and wiring) needs insulatingmaterial to serve as a separating materi-al, sheathings and coatings. Prior to 1910,moldable isolating materials were eithermica,wood,porcelain or a composite ma-terial such as compressed mica with shel-lac as binder, vulcasbestos (a vulcanizedmixture of rubber and asbestos) or moreheat-resistant, rubber-free insulating ma-terials with fillers such as asbestos, slateor marble powder, and natural resins(shellac or copal) as binder [18], while for

56-61_PE110402_PE5 07.05.2010 11:08 Uhr Seite 57


58


wire,gutta-percha, rubber, shellac and co-pal coatings found use.

In 1887, the Robert Bosch company inStuttgart, Germany, introduced a magne-to for stationary gas engines. In 1897, asimilar magneto was used for the firsttime in an motorcar engine. This solvedone of the greatest problems in early au-tomotive engineering. The years 1901/02saw the development of a high-voltagemagneto, which made it possible to buildever faster gasoline engines [19]. The typeZF4 magneto of 1911 [20, 21] containedphenolic resin – only one year after Bake-lite was first produced.A 1925 issue of theBosch Magneto, the “Newspaper for Em-ployees of Robert Bosch AG”, describedin detail which components of an auto-mobile’s electrical system are being man-ufactured from Bakelite: e.g. distributor,current pickup for the ignition coil, mag-neto cover, wiring connectors, variousconnecting plates and bushings used forthe cover [22]. Furthermore, ignitioncoils, fuse boxes and electric switches ofphenol as well as battery cases of synthet-ic Buna rubber were being manufacturedby no later than the 1930s [1]. Starting inabout 1930, production of PVC copoly-mers with good properties could be foundin the electrical industry (Mipolam,Igelit) [23 to 25].

In Germany, coating of electric cableswith an “acetate coating” made of cellu-

lose acetate (Cellit/Cellon) [26, 27] beganin 1904/05. With production of the firstsynthetic plastic by Leo Hendrik Baeke-land, the phenolic resin Bakelite, in 1910in Erkner, Germany, outside Berlin, pro-duction of electrical insulating materialswas also revolutionized. For electrical ca-bles, this led to phenolic resin coatings

[28], but also sheathing materials such asphenolic resin-laminated paper (e.g.Hares laminated paper [29], Pertinax)[23]. Starting in 1925 alkyd resins, and in1926/30 urea resins [23, 30] came into useas raw materials for coatings and lami-nates.

Interior Components

The steel pipe and wooden coaches builtat the end of the 19th century wereequipped with only a few operating con-trols and stationary interior objects. Af-ter enclosed vehicles became increasing-ly common in the 1920s (steering,gearshift and brake levers were no longermounted on the outside), attention fo-cused more on the “interior” of the vehi-cle. Over time, all operating controls weremoved to the interior, with the majoritylocated below the windshield in the “in-strument panel”. Whereas the steeringwheel and brakes were initially made ofwood and metal in the early days, the newsynthetic materials were used more andmore as of the 1930s. The DKW/AutoUnion in Zschopau/Zwickau, Germany,used compression molded phenoplasticcomponents for the interior of its auto-mobiles after 1934,e.g. for the instrumentpanel of the DKW F4 [31]. Figure 4 showsan example of a DKW F7 dating from1937 in which the instrument panel –compression molded from the (finelyveined) Hares phenolic compound (H.Römmler AG, Spremberg, Germany,

Fig. 3. Ford Model A with windows made of safety glass, laminated with cellulose acetate, 1927 (photo: Wikipedia)

Fig. 4. Interior of a DKW F7 Master Class dating from 1937. Instrument panel, switches, shift leverhandles and steering wheel made from phenoplast (H. Römmler AG, Spremberg), seats covered withartificial leather (photo: Deutsches Museum, Munich, Germany)


56-61_PE110402_PE5 07.05.2010 11:08 Uhr Seite 58


59

>


Kunststoffe international 5/2010

>

[32]) – contained also knobs, switches,gearshift handle and steering wheel [1,33]manufactured from this material. Like-wise, ashtrays (England, starting in 1936[34]), the speedometer housing and dialas well as illuminated indicators for low-and high-beam headlights shifted to phe-nolic resin at this time, while steeringwheel covers used synthetic Buna rubber[1]. After 1936, the thermoplastic cellu-lose acetate was used to manufacture doorhandles, window cranks and holders in-stead of metal (Tenite, USA) [35], and in1938 also the new polystyrene (Trolitul,Dynamit AG, Troisdorf) (Fig. 5) [36].

Along with other materials, artificialleather also came into use as a coveringfor interior surfaces. It consists of a tex-tile backing material and a film formertogether with pigments and fillers. Theearliest such film former for artificialleather was a rubber coating with a lin-seed oil varnish. Embossing gave this ar-tificial leather its leather-like surfacestructure [37]. Artificial leather contin-ued to be manufactured from celluloseacetate-based material [38, 39], and start-ing in the mid-1930s also from PVCcopolymers with plasticizers [40].

In 1939, sun visors made from thermo-plastic PVC made their first appearance[41].

The seats in the DKW F7 shown in Fig. 4[1] as well as the seats in a special bus dat-ing from the end of the 1930s (Fig. 6) [42]were likely covered with PVC-based arti-ficial leather.

Use of Resopal laminated panels forheadliners and door panels also repre-sented new applications (Fig. 6) [42]. Plas-tic grip bars in buses also debuted [1].

Technical Equipment

Various other types of polymer materialalso came into wide use for technicalparts. Steering linkage joints with bush-ings made of synthetic resin, bearingcomponents and gears made of phenoliclaminates as well as compression moldedgasoline fuel pumps were installed in ve-hicles [1, 12]. Buna seal rings were em-ployed to ensure reliable sealing of the en-gine’s crankshaft and driveshaft [1]. Bythe end of the 1930s, a variety of Bunagrades were used for lubrication-free wa-ter pumps, unbreakable and oil-resistant

fuel lines, high-pressure brakelines, engine mounts, sup-ports for universal joints, cou-plings and shock absorbers[1]. Lastly, brake linings at thistime consisted of Buna andmetal wool [1]. Today,polyamide, polypropylene,modern rubbers and manyother synthetic polymers arefound in these applications.

Exterior

Following the initial “horse-less carriage”era, the shapes ofautomobiles became more“stylish”and, for instance, fea-tured “running boards” afterthe first decade of the 20thcentury, see Fig. 3. They initial-ly had a rubber coating, butthis was replaced by PVC inthe 1930s [1]. Rubber is stillused today for windshieldwiper blades, initially natural

rubber but then synthetic rubber startingin the 1930s [1]. License plates in the1930s were manufactured from the hardyet flexible PVC grade Astralon [41].

Body

The original motor vehicles were openmetal (left Title photo) or wooden carriages.Fabric tops were added later to protectagainst the weather. Over time, the en-closed sedan became more and morepopular. This required a superstructure,i.e. a body, on the undercarriage. Initial-ly, this body was “not self-supporting”, i.e.the enclosing parts were mounted direct-ly on the undercarriage or frame. For in-stance, some of the body panels of theHanomag 2/10 HP dating from 1924/25(sometimes called the “racing lawnchair”) were made of inexpensive, gluedplywood [43, 44] (Fig. 7) [45]. At the startof plywood fabrication, that is, about1893 [46] casein glue, gluten glue and lat-er blood-albumin glue were used. Suchunmodified protein-based glues havelimited resistance to moisture and heat,are subject to attach by mold and putre-factive agents, and provide only limitedadhesive strength.Since about 1903, treat-ment with formaldehyde to initiate cross-linking of protein-containing substancesresulted in more resistant glue films [47].After 1910, phenolic resin binders, andabout the mid-1930s, aminoplast adhe-sives came into use.

For weather proofing but also for ap-pearance reason, the plywood parts werecovered with artificial leather. In the Wan-derer W10/II dating from 1928, the com-ponents of the upper body were laminat-ed with cellulose acetate-based artificialleather [39], while the luggage compart-ment at the rear used artificial leatherwith a rubber coating finished with a lin-seed oil-based varnish [37, 39].

Fig. 6. Interior of a bus with seats covered in PVC-based arti-ficial leather and Resopal laminated panels for headlinersand doors, end of the 1930s (photo: [42])

Fig. 5. Poly-styrene in placeof metal for doorhandles, windowcranks and hold-ers (photo: [17])

56-61_PE110402_PE5 07.05.2010 11:08 Uhr Seite 59


60

The alternative to the expensive steelsheet components or the relatively sensi-tive artificial leather-covered plywoodpanels was plastic. In 1935/36, the firstexperimental version of a “plastic body”was presented by the Auto Union Chem-nitz/Zwickau, Germany, [31]. This firstattempt involved the front doors of theDKW F5, made from compression mold-ed Hares phenolic resin-laminated paper-based material which were manufacturedby H. Römmler AG, Spremberg. Theclaim of company director Kuntze to beconsidered the inventor of the plastic carbody lead to patent infringement claimsinvolving the Auto Union, which, as aconsequence, turned to the competitor,Dynamit AG in Troisdorf [31]. In 1937,this company started to supply body pan-els made from an improved phenoliccompression molding resin that usedcrape instead of paper sheets. A furtheradvancement came with the moldingcompound called Pete, which contained

60 % sodium cellulose as filler. For thismaterial, Dynamit AG purchased in 1937what was then one of the largest pressesbuilt to date and having a force of 5,000 t[1, 31, 48]. In 1939, parts of an experi-mental version of the F8 sedan were man-ufactured from a phenol resin-basedmolding material (Fig. 8). Since extensivecatapult trials showed that the compres-sion molded body parts were equivalentin a “crash test” to their steel sheetequipped competitors at that time, onlythe outbreak of Word War II preventedlarge-scale production.

In the USA, the first attempts by Fordto built a car body based on phenolicresin with added, wood, flax and hempfibers was not presented to the public un-til 1941 [49].

After the war, the IFA F8 was producedat the car factory in Zwickau in the GDR(East Germany) as the successor to thealmost identical DKW F8 between 1949and 1955. Relying on the previous work

conducted by the Auto Union as regardsresin body components and because ofa shortage of steel as a raw material, thehood and roof were compression mold-ed of phenolic resin with a cotton fillerstarting in February 1953 [50]. In 1954,the first prototype of a model called theP50 was manufactured. A preproductionseries of 50 vehicles was built in Zwick-au in the year 1957, originally called theP 70, and then later the Trabant [31].Starting in 1959, the Trabant 500 wentinto volume production at what was nowthe VEB Sachsenring AutomobilwerkeZwickau (Fig. 9) [51]. The “Trabbi” wasproduced in various variations untilApril 1991.

But even in West-Germany at AutoUnion, Ingolstadt, the idea of a plasticbody had not abandoned. Experimentscontinued on concept cars (DKW STM II3-seater, STM III 4-seater) with plasticbodies until 1957 [52]. Some 230 modelsof the DKW Monza were built in 1956. Itfeatured a new body design based on glassfiber-reinforced polyester (GF-PE) (Fig. 10)[53], a composite material used for thefirst time to build the 1953 Corvette fromChevrolet (General Motors) [54].

This development marked the begin-ning of a new chapter on plastics in thecar industry, one that continues today.

Current Status and Outlook

To even attempt to document thedevelopments in the field of plastics forautomotive use after World War II wouldfar exceed the guidelines set for this arti-cle.

Individual aspects in the areas of tech-nical equipment and interior applicationshave undergone enormous expansion.Production of high-density polyethylene

Fig. 7. Hanomag 2/10 HP sedan with plywood body panels, 1924/25 (photo: Wikipedia)

Fig. 8. Body panels of the DKW F8 produced from phenolic compressionmolding compound, 1939 (photo: August Horch Museum, Zwickau, Germany)



Fig. 9. Body panels of the Trabant produced from phenolic compression molding compound withcotton filler (photo: August Horch Museum, Zwickau)

56-61_PE110402_PE5 07.05.2010 11:08 Uhr Seite 60


fuel tanks [55] as well as headlight andtaillight housings in polycarbonate can benamed as just two examples.

From the technical standpoint, it is en-tirely possible to build car bodies of plas-tic today. In addition to the relatively “ob-vious” benefits (e.g. low weight, weatherresistance, strength and freedom fromrust), the deformability characteristics ofthe high-tech plastic composites used to-day are as much as four times that of steelor aluminum sheet metal in terms of ab-sorption of impact energy [56]. Howev-er, these materials and processing tech-niques are still relatively expensive andare more likely to be found in the aero-space/aircraft sector or in spectacularshort-run vehicles, e.g. exclusive sportscars (right Title photo). The path to lighter-weight cars and thus more cost-effectiveproduction is taking shape in the form ofindividual body components such asbumper fascia, fenders, side doors, lug-gage compartment lids, rear spoilersmade from a variety of glass or carbonfiber-reinforced plastics. Foamed poly-urethane composites with glass fiber, car-bon fiber or natural fiber mats (hemp,sisal and flax) represent the current stateof development [57].

Today’s automobiles contains, on av-erage,170 kg of various plastics.Althoughthey are exceptionally light, their percent-age of the overall weight has increasedmore than tenfold in the past 50 years.The percentage of plastics in a car will in-crease further. Environmental compati-bility and recyclability will be especiallyimportant aspects of the materials of thefuture [58].�

REFERENCESThe extensive literature sources can be found atwww.kunststoffe-international.com/A023

THE AUTHORDR. DR. H.C. DIPL.-CHEM. GÜNTERLATTERMANN, born in 1943, was,from 1978 to 2008, acad. director ofMacromolecular Chemistry I at the

University of Bayreuth. Since 2007, he is chairman ofthe German Liquid Crystal Society (DFKG). In 2005, hefounded the German Society for Plastics History(dgkg) and has served as chairman ever since. He alsofounded the electronic journal for plastics history “e-plastory” (and serves as editor-in-chief).

61Kunststoffe international 5/2010

Fig. 10. DKW Monza with glass fiber-reinforced polyester body 1956 (photo: Wikipedia)


56-61_PE110402_PE5 07.05.2010 11:08 Uhr Seite 61


Documents

(photo: [59]) From Rubber Tires to Plastic Cars · 2010. 11. 28. · more as of the 1930s. The DKW/Auto Union in Zschopau/Zwickau, Germany, used compression molded phenoplastic components