Why are car windows & windshields glass and not a kind of plastic?
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Glass doesn’t scratch as easy (from wipers or sand from the road) as plastic, it doesn’t break down in sunlight, and it doesn’t warp from high temps, wind, or temperature changes.
Your windshield is actually formed from multiple layers to make it very difficult to break. The other windows are made of tempered glass, which shatters into little beads rather than long shards when it breaks
There are several reasons for this.
First, glass is a much better conductor of heat than plastic, so it can more quickly remove the heat from the hot glass surface on a sunny day. This is important because it helps keep the interior of the car cooler.
Second, glass is much more shatter-resistant than plastic. This is important in the event of an accident, as it helps to protect the occupants of the car.
Finally, glass is a much better optical material than plastic. It transmits light more efficiently and provides a clearer view for the driver.
Airplane cockpit windows are often a type of acrylic which is designed to deal with the extreme temperatures and winds while you fly through the atmosphere. Put simply, you just don’t need that much engineering for car windows and glass can be made more cheaply and is easy to see through. With laminated windows, the risk of hurting yourself with them is low in a cash.
Plastic will cloud up due to UV and also get scratched to hell. Look at headlights of an older car.
I have plastics windows believe it or not. Let me just tell you it’s so loud on the highway that I have to blast my music to drown it out. Also they’re not able to be rolled down like a normal window. Glass is cheap and believe it or not very strong. My dads a fire fighter and has taken an axe to a window before and the window didn’t break.
In addition to the other comments they are made of tempered glass so they break [like this](https://res.cloudinary.com/dpcbzfiye/image/upload/w_1080,c_fill,dpr_auto,f_auto,q_auto,fl_progressive/v1534969351/kowuvlbs13v4vbvzd6gw.jpg) and can’t impale you.
Plastic windows do exist – they’re usually just bulletproof polycarbonate laminates. Layers of plastic sandwiched between layers of scratch resistant glass.
… which would be hard to break if you needed to escape your vehicle. And prohibitively expensive.
Glass windows are surprisingly inexpensive to manufacture compared to expensive plastics which share the same desirable characteristics – e.g. scratch, heat, and UV resistance.
Lastly, most modern windshields, not your side windows, do include a plastic inner layer which helps prevent the window from shattering completely into the cabin when it’s broken.
My plastics manufacturing professor in engineering school explained it simply like this: you’d go splat against the windshield in an accident because the plastic wouldn’t shatter. There are acrylics that would otherwise be just fine for car windshields and are used in aircraft and in layers for bulletproofing. However, safety glass breaking the way it does is a good thing in accidents where the person hits or goes through the windshield. Since it breaks, your head doesn’t get the full force of impact of you going 60 pretty much into a wall. There’s also getting out of the car in an emergency to consider as well.
my two things to point out are:
Have you looked at how bad a 10 year old car’s headlights are? faded foggy and yellow is not what you want in a windshield you’re supposed to see out of.
and for side windows how do you get out of a car in an emergency if the windows are jammed and you also not are unable to easily break them and crawl/swim out
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