Infrared Absorption Enhances Comfort
Smart fortwo Features Heat Absorbing Panorama Roof of Fracture-Resistant Polycarbonate
Webasto SE in Stockdorf, Germany, supplies the fixed panorama roof for the third generation of the smart fortwo. The 1.2-m2, transparent roof panel is made of the lightweight material polycarbonate (type: Makrolon, manufacturer: Bayer MaterialScience, Leverkusen, Germany). The roof system admits a lot of light into the interior, creating a pleasant, generous sense of space for the passengers. Visually, it is a perfect extension of the front windshield.
The technical highlight of the roof system is its ability to absorb solar energy and thus prevent the interior from heating up too much. This is made possible by infrared absorbers integrated into the polycarbonate. For the first time, the product Makrolon AG2677 is being used for the new smart in the color- and temperature-stable, heat-absorbing color 771079.
The infrared absorption is also beneficial from an ecological point of view. If the interior heats up less, there is less need for cooling from the air-conditioning system. And this reduces fuel consumption.
The polycarbonate material is extremely impact-resistant, weatherproof and lightweight. A roof made of polycarbonate can be up to 50 % lighter than a glass equivalent. The plastic panel on the new smart fortwo weighs only 9.8 kg. Not only does the low weight reduce the fuel consumption of the car. The roof also has a favorable impact on the driving dynamics, as it shifts the vehicle’s center of gravity further down.
The roof is manufactured by means of two-component injection compression molding. In addition to the transparent Makrolon AG2677, the black-colored polycarbonate ABS blend Bayblend T95 MF is used as the second component. It enables the integration of additional functions such as screw bosses on the bottom side of the roof. Attached to them is the infinitely adjustable fabric roller blind used to control the brightness of the vehicle interior.
A coating layer makes the panorama roof resistant to scratching and weathering impact. The roof system is the world’s largest injection-molded, transparently coated car roof with an infrared absorber.
Translated from Kunststoffe 3/2015, p. 13.
Covestro Deutschland AG
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