Safety Tips

New Developments in Safety Glass
By Scott Memmer
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Safety glass is one of those areas we hear precious little about in automotive circles.

Why is it that we get inundated with press releases about the latest shock absorber or the newest engine with 12 valves per cylinder, and almost nothing about safety glass?

You could argue that the reasons are, well, transparent. After all, glass isn't a very sexy subject, while talking about cylinders and pistons will raise the pulse of even the most jaded enthusiast.

But think about it: After brakes and seatbelts, what's more important to the safety and comfort of a car's occupants than glass?

Here in Los Angeles, where our offices are based, it's a veritable fashion show out there on the freeways. In a town where breast implants outnumber brain surgery by a wide margin, it's no wonder that we spend so much time gawking at one another in our cars.

But glass -- hard, simple, clear glass -- makes it all possible. Without glass, we wouldn't be able to stare. Without glass, we'd be running into each other.

It's common knowledge that the skin is the largest organ on the human body. So, too, glass plays a primary role in covering and protecting your car.

Recent advancements in automotive glass have paved the way for a new family of products. Volvo, an automaker long identified with safety, has now joined Mercedes, BMW and other European automakers with the introduction of Enhanced Protective Glass (EPG), a cutting-edge technology developed by Solutia Inc., a St. Louis-based chemical company. Currently available as an option on the S80 sedan and the new V70 wagon and sport wagon, EPG has a number of benefits over traditional automotive shatter-proof glass, such as:

• reduced weight
• protection from ultraviolet light
• theft deterrence
• protection from occupant ejection during accidents
• protection from outside projectiles
• reduction of unwanted traffic and highway noise

Volvo's Enhanced Protective Glass is made from polyvinyl butyral (PVB), a new kind of laminated glass specifically developed for side and rear windows of motor vehicles. Marketed under the trade name Saflex PVB, the product is made by laminating a sheet of polyvinyl butyral (PVB) between two sheets of glass under heat and pressure. This is similar to the process used in manufacturing windshields, although it is engineered to 3.8 millimeters, much thinner than a windshield. (Windshield glass typically runs thicker, between 4 and 5 millimeters, sometimes more.)

The idea for automotive safety glass goes back to 1905, when Englishman John Crew Wood received the first patent for laminated safety glass. Believe it or not, the original interlayer was made from natural tree resin. Advances followed. In 1910, an inventor named Douard Benedictus proposed using a gelatin to adhere the glass and plastic layers. His product became known as "Triplex" glass and was used during World War I for goggles, gas masks and windshields in airplanes. It also found its way into automobile windshields.

In 1938, Monsanto developed the Saflex plastic interlayer, the precursor to Saflex PVB. (In fact, Solutia Inc. was a part of Monsanto for many years, until they spun it off three years ago.) Solutia also makes a similar product for the home market, called KeepSafe glass.

According to Carl Moskowitz, director of public affairs for Solutia, traffic and highway noise is another reason -- for some, the main reason -- that automakers are using Saflex PVB. He cited Mercedes-Benz and BMW as two manufacturers that employ the technology mainly to reduce noise. Saflex PVB offers a 6-decibel reduction of highway noise over conventional side window glass, and, more importantly, this reduction comes in the frequency range of 2000 to 6000 Hertz, which is right in the middle hearing range for most human beings. Moskowitz claims the difference is audible and significant. (This would explain why manufacturers of upscale automakers have been the first to embrace Saflex PVB.)

Another potential significant benefit of the stronger glass is the prevention of occupant ejection during traffic accidents. Since up to a third of all Americans apparently haven't figured out what that fabric strap next to their seat is used for, a number of occupants, many of them young people, continue to die through vehicle ejection during a crash. Moskowitz cited NHTSA figures in the range of 1500-2000, and stated unequivocally, "More people are killed by ejection than entrapment." Moskowitz also indicated that NHTSA is conducting tests involving Saflex PVB. Frankly, this strikes us as a more sound solution than airbags that kill innocent children. And then there's the theft-deterrence aspect. While we've yet to see a technology that can stop a crook who really wants your car, as the picture on the right illustrates, this may slow him down enough to send him on his way.

All this good news is tempered somewhat by our very real concerns about entrapment. Granted, Saflex PVB offers a lot of benefits, and perhaps the good news outweighs the bad, but what about those rare instances where a person becomes entrapped in a vehicle in a canal in Florida, for instance, and can't escape?

To that question, Moskowitz indicated that Solutia engineers recently got together with a group of Emergency Medical Technicians (EMTs) to discuss extrication issues.

Here are a few quotes from a Solutia press release recapping that get-together.

"'Once we identify a side window as being EPG, we will have no problem dealing with it in an extrication situation,' says Ron Moore, a fire service instructor and nationally recognized extrication specialist from the Plano, Texas, fire department.

"'EPG is a big plus in terms of occupant safety,' says Ron Shaw, editor of Extrication.com and a member of the Plymouth, Mass., fire department. 'From the standpoint of emergency medical technicians, ejection is a bigger concern than entrapment.'

"'We know from our real-world extrication experience that staying in the vehicle in a motor vehicle crash gives you your best chance to survive,' Moore adds. 'The benefits of EPG -- protection from ejection, protection from flying glass -- far outweigh any concerns or challenges that we will experience as medical rescuers.'"

We still have some concerns in this area, and there will be occasions when a life could be lost due to Saflex PVB glass. It would appear, however, that the benefits far outweigh the disadvantages.

Virtually all of the cars currently using Solutia's glass are European automakers, some as optional equipment, others as standard. We've included a chart below detailing manufacturers and model numbers.

Moskowitz indicated that several American manufacturers are currently in the testing phase and may soon implement Saflex PVB glass in select models.