THE WONDERS OF AUTO GLASS

How many of us ever look through our cars’ windshields and ask ourselves, “How is this made?” or “What exactly does this do besides allow us to see the scenery when we are driving?” Many of us probably don’t give it a second thought, but auto glass is an integral component of a cars’ safety systems and warrants a closer look at how it is manufactured and the safety properties it offers.

When a car company produces ads heralding their vehicles’ new safety features in the Mississauga auto glass area, they rarely talk about, or even mention the windshield or other windows. It is a little known fact that this type of glass was designed and fabricated with the safety of passengers in mind. The function of this remarkable combination of materials, such as silica sand and chemicals, is far different from regular household glass despite their similar appearances.

Let’s first examine the daily encounters of your vehicle as it travels through its’ lifetime. We all know that the road conditions today can be perilous at times. Your car will no doubt encounter a wide assortment and number of things such as potholes, rocks, debris and fender benders in its’ lifetime. If your auto glass was manufactured out of a standard type of glass, such as household glass, it would shatter into large and dangerous shards when you encounter the first pothole! This is a direct result of the strain put on the glass during your normal every day driving. Because of this, using standard glass would be an extremely dangerous practice.

You may be asking by now, “What really prevents auto glass from shattering at the slightest chance meeting with a pot hole?” The answer is quite simple. Automotive glass is manufactured by using two different processes that yields two different types of safety glass. This safety glass thus protects the structure of your vehicle and also the precious cargo inside.

The first type of safety glass is called laminated glass. This is used in the windshield of your car. The second type of safety glass that is used for the side and back windows is typically known as tempered glass.

These two types of glass have different functions and properties, but when used together, they merge to become an integral factor in keeping you inside the vehicle during an accident, shield you from flying shards of glass and projectiles, maintain the vehicles’ rigidity in a rollover and allows the passenger side airbags to protect you when it is deployed.

What is the role of laminated glass in an accident? First of all, without laminated glass, the passenger side air bag would not be able to deploy correctly and function as it was designed to do. When a passenger side air bag deploys in the Mississauga auto glass region, it bounces off the windshield and then towards the passenger. It releases in a time frame of approximately 1/30^th of a second and can exert up to 2,000 pounds of force. Can you imagine the damage this force can do to a human body if the force was not absorbed before it came into contact with the passenger? Since it bounces off the windshield first, the laminated glass has to absorb both the speed and the force in order to protect the passenger. If the force and speed was not absorbed, then a passenger side air bag would surely prove fatal to a passenger instead of saving them, thus defeating the purpose of the air bag.

Laminated glass also serves to keep occupants inside a vehicle during an accident. In the past, there were many instances and fatalities where occupants were ejected from a vehicle through the windshield because the glass simply wasn’t strong enough. Today’s laminated glass is strong enough to keep occupants inside, and thus, provide more security.

In addition to absorbing the force of air bags being deployed and keeping occupants inside the vehicle, laminated windshields also add to the strength and rigidity of a vehicle’s roof. It helps to prevent the roof from buckling down completely on the occupants during a roll over.

Tempered glass is just as important to a car’s safety system as laminated glass, but it differs greatly in both form and function. This type of glass is used for the surrounding glass and the back window, namely the sidelites and backlite. When tempered glass breaks, it shatters into small, dull pieces. The tempering process significantly adds to the strength of this glass, thus producing a glass that does not break each time you hit a pothole or close the door.

Now that we have looked at the various functions and safety features of auto glass in the Mississauga auto glass district, it is time to discover the different manufacturing processes of laminated and tempered glass.

Laminated glass, simply put, is a layer of polyvinyl butyral (PVB) sandwiched between two pieces of glass. These are then sealed by a series of pressure rollers and then heated. This combination of pressure and heat mechanically and chemically bonds the PVB to the auto glass. The mechanical bond occurs through the adhesiveness of the PVB, while the chemical bond is created through hydrogen bonding of the PVB to the glass.

It is the sandwiched layer of PVB in laminated glass that allows the glass to absorb energy in an impact and gives resistance to the penetration of flying projectiles. The PVB also deflects up to 95% of the ultraviolet rays from the sun.

Tempered glass is created by heating and then rapidly cooling the glass to room temperature by quickly ushering it through a system of blowers. The surface of the glass cools much faster than the center and contracts, which causes compressive stresses. At the same time, the center of the glass expands because of its’ temperature. This produces what’s known as tensile stresses. In simple terms, picture a piece of glass that could be stretched to a certain length (tensile stress), while being pushed down and compressed (compressive stress) simultaneously. By creating both of these stresses, manufacturers are able to produce a glass that has 5 to 10 times the strength it originally had. Bear in mind that the tempering process leaves the edges on a typical piece of tempered glass very weak. This is caused mostly by the rapid release of heat during the cooling phase of the tempering process. To help compensate for this, the glass is ground down on the edges.

Now that you have discovered the safety features of auto glass and the manufacturing processes, it would be a difficult chore to look through your car’s windshield ever again and think that the only use is to allow us to see where we are going. On the contrary, auto glass is so much more!!!