As automakers face slowly diminishing returns in their attempts to make internal combustion engines more efficient (while facing huge challenges in electric, hydrogen and other alt-fuel drivetrains), they are looking ever more closely at alternative materials to improve efficiency (and, to a lesser extent, driving pleasure) through weight-savings. Perhaps the biggest emerging trend in this area, especially at the higher end of the market, is in the use of carbon fiber, which is being actively pursued by automakers like BMW, Toyota, Lamborghini and Daimler. But, as WardsAuto points out, there’s another material that’s trying to earn a place in the lightweight cars of tomorrow: polycarbonate plastics.
Polycarbonate windows weigh half as much as glass, and because they are made with injection molding they can come in shapes that can’t be imagined with glass.
However, the material is more expensive. To get auto makers to convert, Sabic and its main material competitor, Bayer MaterialScience, have to sell the idea of integrating other parts into the plastic mold that makes the window.
For example, says Umamaheswara, “on a liftgate, a lot of features can be integrated, and if the manufacturer is short of room in the factory, it can be delivered as a module.”
A modular liftgate could include the window, cladding for the D-pillar, a roof spoiler, the high-mounted rear brake light, a rear wiper foot, handles and logos. When all those processing costs are included, he says, polycarbonate is competitive with glass and metal.
These unique assemblies are just one of the growth areas for polycarbonate plastics. Already, Wards reports that the material has become standard for headlamp covers, and when it comes to high-end, cost-no-object projects, well:
Bugatti developed a targa top for its Veyron 16:4 Grand Sport roadster in both glass and polycarbonate from Bayer, and the plastic version chosen had a weight savings of 13.0 lbs. (5.9 kg)
But that’s not the only project that has seen polycarbonates used to create light-weight windows and lower centers of gravity:
The Smart Fourtwo was the first to use polycarbonate windows, with fixed rear sidelites starting in 1998. Supplier Freeglass has made about 4 million plastic windows for Smart, Mercedes-Benz, the European Honda Civic and the SEAT Leon.
But don’t expect to see many polycarbonate plastic windows or other large subassemblies in many mass-market cars for the next few years. Even though firms like Sabic are coming up with special plastics that, if used on panorama roofs, will not just lower weight but improve insulation as well, they don’t expect major-volume projects until more EVs start coming to market, in the 2014-2015 timeframe. In the meantime, if you’re already raring for some polycarbonate windows, you’ll have to spring for a high-price Euro-spec road-racer like the Renaultsport Mégane R.26.R.