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Plastic Car Windows: One Way To Save Weight

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2014 Fiat 500L

2014 Fiat 500L

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Traditionally, car windows have been made from laminated glass.

It's strong, shatter-resistant, and... err... transparent. Obviously. But it's also rather heavy, and as increasingly weight-conscious car manufacturers are looking for ways to shed weight, glass could now be on the diet list.

Its replacement could be polycarbonate, says The Detroit News (via Motor Authority).

While polycarbonate has been used for some time in race cars, as well as more recently in some performance road cars, it's now set to appear on the humble 2014 Fiat 500L wagon, to help cut weight.

Glass can make up 100 pounds of a car's weight, but its equivalent in polycarbonate could be half that.

It wouldn't be used throughout, instead seeing service in rear windows or sunroofs, reducing weight where appropriate.

It could realistically be used for side windows, but there's a safety issue here. Not that the plastic is too weak, but that it's too strong--in an accident, first responders would have trouble breaking through to injured or trapped occupants. As a result, they're prohibited for use as windscreens or side windows.

Scratch resistance, hazing and cost are all cited as potential stumbling blocks. UV-protecting layers can prevent hazing under years of sunlight (something you can often see on older polycarbonate headlamps) but additional layers would be required to prevent scratching.

Polycarbonate windows can also be twice the cost of glass windows, though price could come down if the technology is more widely adopted.

Ford is just one company currently running trials, and is near to completing a 10,000-hour environmental durability testing cycle on the windows--if successful, polycarbonate windows could appear in the new Transit Connect due later in 2013.

[UPDATE: Ford spokesman Mike Levine later contacted Green Car Reports regarding the sentence above, saying that Ford has no plans to use plastic windows in the upcoming 2014 Ford Transit Connect--a fact subsequently changed in the article from The Detroit News that was originally cited by our author.]

There's another benefit of the windows, despite the extra cost: Design.

Compression moulding techniques allow the plastic to be formed into all manner of shapes much more easily than glass. Windows could be even formed into aerodynamic shapes themselves, without compromising strength or increasing complexity.

The cool hexagonal sunroofs on the Kia Cross GT concept launched at Chicago? Not difficult at all to produce in polycarbonate.

It's unclear as to how many cars will use polycarbonate windows, though it's likely to be one facet of the myriad techniques used to reduce weight in future cars.

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Comments (4)
  1. I hate clear plastics because it develops scratches just from repeated cleanings so you can't even try to keep it looking good. They can keep the glass it's steel that needs to go, so lets get the carbon fiber revolution going first.
     
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  2. Yes CDspeed, so I wonder what the coatings are that would protect from scratches, how effective they are, and their costs.
     
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  3. Jeff & CDspeed, years ago, I worked for a large supplier of adhesives/sealants/coatings and we worked on protective coatings. Back then, they weren't well developed and the push for lower emissions/better mileage was not urgent, so the push wasn't strong yet.

    I don't know where we are now, but my guess is that, like steel, you'd lose much of the savings after additional costs to improve the polycarbonate. Steel is heavier than aluminum, but also more expensive. Magnesium is lighter than Al, but again, more expensive.

    Trade-offs all around. I think this has potential is some smaller applications (meaning glass size, not vehicle size) but that's just a quick guess.
     
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  4. Most if not all headlamps are now polycarbonate and considering their location do not have a problem.The Smart cars roof has been polycarbonate for some years and certain Citroen BX models between 82 to 94 had a tinted C pillar of the stuff. Citroen had a problem with it crazing after a few years but it was early days in its development.I can see it being widely used especially in conjunction with carbon fiber bodies.
     
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