Laminated and Tempered Glass
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Laminated Vs. Tempered Glass
Ever cruise down the highway and wonder why your windshield cracks but stays put, meanwhile a tiny pebble hitting your side windows will shatter it into a million pieces? The answer lies in the clever science behind car windows – laminated versus tempered glass.
The Laminated Lifesaver
Your car's windshield is essentially just a high tech sandwich. Two layers of glass encase a clear plastic interlayer, usually made of polyvinyl butyral (PVB). This PVB acts like a spiderweb, holding the glass together even if it cracks under impact. The result? A shield for you and your passengers. Even in a collision, the inner layer stays intact, preventing dangerous shards from flying inwards.
Tempered Glass
Now, let's shift to your side and rear windows. Here, tempered glass takes center stage. Tempered glass is created from heating glass to a very high temperature then rapidly cooling it. This causes the glass to have internal stress that makes it much stronger. But if a strong enough force breaks it, tempered glass shatters into countless, small, blunt fragments.
This shattering behavior might seem counterintuitive, but it's a safety feature. Compared to regular glass breaking into large, sharp shards, tempered glass reduces the risk of severe lacerations. That's why it's ideal for side and rear windows, where the main concern is preventing accidental breakage from stray objects or during emergencies where an exit might be needed.
Why Not Have All Laminated Glass?
Laminated glass might seem like the clear winner, so why aren't all car windows made from it? The answer boils down to a balancing act. Laminated glass is heavier and more expensive to produce than tempered glass. Additionally, rolling down laminated windows requires thicker mechanisms, adding complexity and cost. On top of the cost, tempered glass is needed in case of an emergency where the car's window needs to be broken for an escape or rescue.
Tempered glass offers a good balance between safety and practicality. The windshield is going to attract almost every object on the road leaving the side windows mostly untouched. Tempered glass is strong enough to take a few blows if you wandering pebble does find its way to the side of your vehicle.
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