When we think about the function of a windshield most people typically think about the glass in the front of their car as being there to protect them from the elements, flying debris and bugs when they drive. In today’s day and age though your vehicle’s windshield is so much more than that!
As a fundamental safety feature, your windshield contributes up to 45% structural strength to the roof of your car, and in a rollover, up to 60%. If you get caught in a rollover, the windshield in the car works as a supportive beam and prevents the car roof from caving in and collapsing on you and your loved ones. It also acts as a backboard for your airbags, ensuring proper and safe deployment and aids in preventing passenger ejection from the vehicle in the event of an accident.
Suffice it to say, having the right windshield adhesives (the material used to adhere the glass to the car and keep it safely in place) plays a crucial safety role. The poorer the adhesive, the less reliable the bond between the glass and the vehicle body, which could result in the windshield separating from the car body in the event of an accident.
The Difference Between Windshield Adhesives
The top most common windshield adhesives are as follows:
Butyl
As described by Car Glass Guru: Butyl is a common sealant that was also used as a windshield adhesive back in the day. Butyl is a black tacky substance that works well to seal holes but doesn’t get used as a windshield adhesive anymore. That is because Butyl tends not to cure to a fully solid-state. This caused the windshield to have a very weak bond with the car so that during frontal collisions, the glass would actually eject out from the vehicle. Because of this, when adhering the windshield to the car today, manufacturers now use Urethane. Despite this, Butyl is still a good sealant and can be used to seal small holes. It holds up well against shock and temperature extremes.
Silicone
Although it may be a good sealant for water leaks in some parts of the vehicle, but it is NOT suitable to be anywhere near a windshield. Silicone does not bond to urethane is a big no no in the auto glass industry. Silicone should not be a windshield adhesive and shouldn't be used to bond auto glass parts.
Urethane
As described by Car Glass Guru: Urethane is also a black substance, but it cures full and is flexible. Once Polyurethane is cured, it has a holding strength of 10,000 PSI. This is extremely strong and is more than enough to keep any windshield glued to the vehicle. Polyurethane also works so well as a windshield adhesive because it is flexible. When a car is cornering, it inevitably flexes, and you need a windshield adhesive that can absorb that flex so that the glass doesn’t break.
Today and in the Future, Windshields will be Bonded with Polyurethane Adhesives
Polyurethane is the best choice when it comes to strength, quality and safety. That’s why Aaron’s AutoGlass uses Dupont Xpress30. A 30 minute safe drive away time urethane manufactured by Dupont.
In comparison to other windshield adhesive, DuPont aftermarket products are subjected to the most rigorous OEM testing conditions, including long-term settings such as weatherometers and outdoor exposure.
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