Swen Gestermann, Martin Heusler, Hans-Peter Neuwald,
Bayer MaterialScience AG
Modern plastics allow making light-weight cars with low fuel delivery. Besides it, advanced materials together with completely new technological concepts give ground for numerous ideas concerning plastics in the cars of future. Latest products of Bayer MaterialScience give bright evidence to this
“Ecology safe automobiles should not turn into “declarations on wheels” but first of all give joy of driving” – following this motto the quaintest car of the present-day was created. Having power of 150 hp, it weighs 750 kg only and requires 6.3 l of E85 bioethanol for 100 km (it’s equal to 4.5 l of petrol) – these are only some of the peculiar features distinguishing eXasis, the third fully transparent concept-car made by Bayer MaterialScience AG and Rinspeed design bureau in alliance. Considering that ethanol is almost CO2-neutral, this yellow two-seater roadster, emitting only 20 grams of carbon dioxide in one km, is a truly ecology friendly subcompact automobile. Comparing to a 4x4 with big-volume engine emits 300 grams of carbon dioxide for 1 km.
All the best from BMS
Some peculiar features belonging to eXasis – just as in case with preceding zaZen and Senso – were brought to life with the help of Bayer MaterialScience products. The cigarette-like two-seater car body and bottom side and made of Makrolon® transparent polycarbonate. Other eye-catchers in the passenger compartment are transparent instrument and functional panels. Driver’s tools are soft and warm, and thus are pleasant to touch. This effect is achieved by means of Soft Feel polyurethane cover based on Bayhydrol® and Bayhydur® paint and varnish materials. Metal parts inside the compartment are coated with chrome effect varnish based on Desmodur® and Desmophen® polyurethane varnish. Bends of both seats, placed one after another, are also made of Makrolon® and swifted with a noble metal net. Head restraints and armrests are filed with Technogel®, light-weight, resilient plasticizator-free polyurethane gel, giving a soft and warm feeling. Cables under bonnet are coated with Desmopan®, flexible, wear and chemical-resistant thermoplastic polyurethane. Transparent body parts are made by thermoforming from Makrolon® polycarbonate.
The new concept-car, on the one side, gives impulse for new research and developments. and on the other side is supposed to demonstrate that Bayer MaterialScience already makes materials opening fields for high-quality construction elements mass production. This refers, for instance, to Makrolon®, already being known as a new material for car window glasses and sunroofs.
With its area of 1.2 sq. meters, this polycarbonate sunroof of the new Smart Fortwo is the biggest sunroof presently produced in series. It is made of Makrolon® AG2677 and Bayblend® DP T 95 MF, specialty material brands by Bayer MaterialScience for car glasses. The sunroof itself is produced and supplied by Webasto AG, Schtockdorf, near Munich.
The roof is made by two-component molding in a rotating plate molding machine. By the first injection the transparent outer surface from Makrolon® AG2677 is made, and by the second – the broad frame from Bayblend DP® T 95 MF. The latter is black bulk-colored PC+ABS blend, it is developed by Bayer MaterialScience together with Webasto, and was created specially to be the second component in the described production. Among its advantages is behavior at shrinkage, which makes it possible to produce this module part with small release stresses and almost avoiding sagging, achieving perfect surface quality, despite its size.
The sunroof weight is over 40% lower compared to its glass counterparts. This favors lower fuel consumption, better road stability, and cornering ability, gives huge freedom for design, unreal for glass, and the possibility to integrate fixture elements in parts of construction. As for sunroof size, big potential is still seen here. Modern materials and technologies enable making sunroofs with surface area of up to 1.7 sq. meters. Besides it, there exists a perspective for roof spoilers, highly set lights, pulpit and splashing plates integration.
In the car compartment two promising PC+ABS blends from Bayer MaterialScience are used: Bayblend® T65 XF and T85 XF (XF=ExtremeFlow). They are aimed to make articles resistant to high as well to low temperatures, and also parts supposed to guarantee driver’s and passengers’ safety in the airbag action zone to protect knees from impact effect (produced by airbag cover or frame, anglet trimming and glovebox cover). Compared to standard blend types characteristics, Bayblend® T65 XF and T85 XF, demonstrate flow properties improved almost by 15%. This gives mainly economic profits to the processor. Thus, he can bring down processing temperature, reducing cooling time, and, consequently, processing cycle length. As an alternative, it’s possible to reduce injection pressure, which will give freedom to use smaller molding machines with lower clamping force. Besides, lower die filling pressure, allows producing molded articles with extremely precise geometry using low-damage technologies with lower tension stresses. Prolonging time of exposition to pressure, sagging can be reduced further on. In some cases simpler molds can be used, since due to gating way lengthening, the number of mold channels can be reduced.
Other advantages of new Bayblend® XF are exquisite ageing resistance, high viscosity at low temperatures, and also resistance to severe atmosphere impact. The latter guarantees perfect crack resistance caused by internal stresses at atmosphere effects. This is particularly important at such stages as varnishing, gluing and additional foaming. And finally, both PC+ABS blends are stiffer, then standards counterparts. Together with improved rheology all this gibes opportunities for making light-weight articles with thinner walls without any detrimental effect on their mechanical stress resistance.