By on July 12, 2011

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 BMWToyota, 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.

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40 Comments on “Are You Ready For: Plastic Windows?...”

  • avatar

    How scratch and marring resistant will the material be? How often do we see the “clear” poly-carb headlights that are severly scratched to the point of looking like ground glass. Seems like a safety issue to me.

    • 0 avatar

      The current auto glass replacement companies would move into the windshield polishing business.

    • 0 avatar

      On my cars, polycarb headlights never were all that scratched, but they became yellowish over time. I had one replaced after an accident and then it became very apparent. The yellow tint seems to be in the material as it gets older. It cannot be buffed out.

      • 0 avatar

        3M’s system claims to fix yellow headlights:–

        Apparently, yellowing is limited to a minimal distance below the surface.

  • avatar

    So now our windows can look as nasty as your headlights in a couple of years. Oh yes, I am soooooooo ready for that.

    • 0 avatar

      you can’t compare that to a “fish eye” Ford Taurus headlight that is yellow and scratchy after 2 months… My 2005 Mazda 3 headlight still looks as new.

      Scrape resistance and noise reduction likely are problems besides cost. cost could be reduced if they gain savings from the modular design that was talked about.

  • avatar

    Sabic (Formerly GE Plastics) has been working on these for at least 15 years. I am not sure what the issues have been. Maybe it is simply cost. I suspect that UV stabilization is the biggest issue though. Tints and dark colors really improve the UV stabilization by preventing UV rays from penetrating as far into the plastic. Clear material is the most difficult to stabilize.

    Sabic and Bayer would love to find a new home for Polycarbonate since CD and DVD volumes are down dramatically. These were a huge market for PC.

  • avatar

    Sorry, EN, but this sounds like a story from the 1970s. The utility of plastics is well-established.

    Producing windows from it makes sense, but the cost, abrasion, thermal, and chemical resistance issues will be difficult. Performance specs at -40C are exceptionally limiting.

  • avatar
    Toy Maker

    The 2004 Toyota Rav4 uses (ABS?)plastics for their sunroofs, so this is certainly another step in the right direction.

    The techie in me welcomes the idea, it might even serve to increase side impact protection if used as side windows.

    It could also mean an end to crooks busting windows and stealing things out of our cars.

    However, the movie watcher in me worries about if it will make escaping from an overturned burning car harder.

    As long as they won’t complicate rescue efforts during emergencies I say bring it on.

  • avatar

    I have no problem with the rr 1/4 windows in my 2004 Smart ForTwo.

    The 1st gen ForTwo’s tempered glass panarama roof (prone to shattering when nicked with a stone) was replaced with a polycarb version in the 2nd gen vehicle… this seems to be a net improvement.

    That said, I don’t think polycarb is suitable for any other window on the vehicle … Windshield: Scratches from wipers; Backlite: same; Door Sidelites: Scratches on the inside and outside from the inner and outer belt-line door to glass seals….

    Without the proper stabilizers, or coatings, the material would (as others pointed-out above) be succeptable to crazing, and clouding due to sun damage … bad enough with headlamp covers, potentially fatal, or unaffordable in window/windscreen applications…

    • 0 avatar

      Its an interesting point you bring up, the unsuitability of polycarbonate in window/windscreen applications.

      BayVision, the Bayer polycarbonate windows used in the Smart, is sold for only non-windscreen applications. And don’t expect polycarbonate windshields anytime soon; NHTSA doesn’t allow for it.

      The great hope for polycarbonate windows used en masse are the expansive panoramic roofs seen in dozens of concepts throughout the years. Weight savings and looks pretty. Bayer themselves have been involved with several concepts, including the roof on the Bugatti Veyron Grand Sport.

      However, being that IIHS seemed to be now focused on roof strength for their safety evaluations, don’t expect these panoramic roofs to be used extensively anytime soon.

  • avatar
    Greg Locock

    Interesting that there is no mention of noise. Glass thickness is critical for windnoise in particular, and road noise to a lesser extent. The behaviour of platic as a barrier will be different to glass, and 5cents to a dollar it is worse.

    However, Lexus originally launched with a double glazed side windw, an astute manufacturer might think that a double glazed plastic system might work, especially with different wall thicknesses for the two panes to reduce coincidence effects.

    I am very dubious about scratch resistance in the long term.

    • 0 avatar

      What is the size stability like with temperature variance? Would it be like with plastic body pieces, where panel gaps tend to be huge to allow for expansion? I wouldn’t think that would be desirable with windows that need to seal for weather and wind noise resistance.

    • 0 avatar

      Actually plastic is a far better barrier to noise than glass. Ever see anyone at a wedding hold up a plastic champagne glass and ‘try’ to ping it to raise a toast? Not going to happen. Glass is great at transmitting sound as it tends to vibrate with the sound. Most modern companies touting sound proofing for home windows use plastic instead of glass.

      As for what this will do to the shape of cars in the future, I expect when this type of window is developed and cheaper it will change the shape of modern cars and make the ones that came before them look very dated. As the article states, it can be shaped in many more ways than glass. Given body panels will be heading towards carbon fiber and aluminum (and aluminum blends) cars will get a lot more exciting to look at IMO.

  • avatar

    Can u imagine scrapping ice off the side glass, scratch, scratch, scratch…

    side impact, auto glass shatters into “safe” chunks, poly carb shatters into dangerously sharp pieces.

    Combine with the fogging and yellowing… don’t see it happening anytime soon.

  • avatar

    Sounds like it’s time for someone to invent transparent aluminum. Where’s Scotty when you need him? “Hello, computer.”

    • 0 avatar

      You stole my line! :-)

    • 0 avatar

      Actually, transparent already exists… it’s the synthetic sapphire used in expensive watch crystals. Very scratch resistant… but more shatter prone than regular glass.

      • 0 avatar

        I totally disagree with this comment about aluminum. The military has developed a transparent aluminum using Aluminum oxynitride that can defeat 50 caliber rounds.

        So its here, and it doesn’t shatter.

        But…I imagine its expensive.

        Also how has no one jumped on the idea that polycarbonates (a la lexan) are extremely hard to break, so no more smashing windows with rocks in a sock?

      • 0 avatar
        bill h.

        Guys, transparent aluminum METAL is not the same as sapphire (single crystal aluminum oxide) or Al oxynitride. The latter are compounds of the metal. Transparent Al is still a SF dream, and given the atomic structure of metals, not likely (yeah, famous last words). Oh, and the AlON for transparent armor is still in the development stage–very expensive and difficult to produce with the kind of crystalline structure that makes it transparent and yet holds up to ballistic impacts.

      • 0 avatar

        Aluminum Oxynitride, as of 2005, is $10-15 per square INCH to produce as opposed to bullet resistant glass which is $3 per square inch. AlON would be great for A-pillars and C-pillars, though.

    • 0 avatar

      Yeah. But you first have to find the one missing part of the formula he took out when they left!

      As far as the comment about Lexan windows, Amtrak did that in the 1970’s on their passenger cars and that resulted in nothing but problems with varying degrees of visibility due to scratching and essentially becoming “frosted” and yellowed and they were eventually replaced with glass. I experienced riding in those passenger cars with Lexan outer windows – the inner panes were glass – and they looked terrible and made viewing scenery unpleasant. Not good. I can’t imagine plastic windows in cars, especially windshields.

      Cars will be more “throw-away” vehicles than ever – maybe that’s the plan ater all. Goodbye future restoration and any cars to be considered “classics” – phooey, we’re already there now, aren’t we?

  • avatar
    Robert Schwartz

    How about smaller cars with less electronic crap?

    • 0 avatar

      Won’t sell. The kind of people who like them buy used anyway.

    • 0 avatar

      Less electronic crap means more mechanical and electrical crap. Tens of feet cables that snag, wiring harnesses as thick as a tree trunk and miles long when stretched out, linkages, etc, etc.

      Electronics are good for keeping weight down and reliability up.

      If you want to do something about mass, size is a good start. So is sound dampening, big wheels and throne-like seats.

      • 0 avatar

        Ridiculous gadgets like nav systems and backup cameras count as superfluous electronic crap that mostly just add complexity (and fuel consumption- that electricity has to come from somewhere!).

  • avatar

    Polycarbonate is tough, but is it rigid enough? The windscreen on a modern car is also a load-bearing component, some cars have been known to develop windscreen cracks because of a combination of wear/chips and lots of hard cornering.

  • avatar
    M 1

    This is why the government shouldn’t be in charge of consumer product design.

  • avatar


  • avatar

    Anybody remamber the “Graduate”? What was that one word? “PLASTICS”

  • avatar

    For places that don’t need glass, this is a great idea.

    Have you ever noticed how massive the hatch of, say, a Saab 900, Mazda6 or any minivan is? Much of that is glass. I know I lived in fear of my 9-3’s hatch struts failing. Aside from the front windshield, this could work quite well. You’d need to polish it, but perhaps only a little more frequently than glass** and not at a huge expense.

    ** which does pit and streak; it’s just less obvious in daylight but very, very obvious at night and in a city.

  • avatar

    The Hueys and Cobras I flew in the Army all had plastic windscreens and windows and there was never a problem with visibility. Of course there were two enlisted guys who would polish them on a daily basis. The Cobras had a special hand hammer that could be used to shatter the canopy plastic if you needed to exit post haste.

  • avatar

    I still prefer transparent aluminium.

  • avatar

    Saturn had plastic body panels. It wasn’t a success.

  • avatar

    Well, plastic windows may be harder to break than tempered glass ones, but if any manufacturers start using plastic even just for side windows we can look for a huge replacement market as soon as the local hoods and bored teenagers discover the potential for scratching their foul slogans and graffiti into the plastic wiindows.

  • avatar

    Am I ready for plastic windows? I’ve been living with them for a few years already. The stock plexiglass side and rear windows in my KV Mini 1 and my HMV Freeway have held up okay to a little over thirty years of use with only minor scratching and crazing. They’re showing their age but don’t require replacement. The KV has a glass windshield, so that doesn’t count, but the original Lexan windshield in the HMV is doing remarkably well (much better than the adjacent plexiglass, as one would hope), despite no special treatment. I’d like to think that a properly developed modern polycarbonate could do even better.

  • avatar

    Forget plastic windows- where the heck are the all plastic pick-up truck beds?

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