Lite, Part II
Polycarbonates Offer Many Possibilities for the Automotive Industry
by Leslie Shaver
This is the second in a two-part series about NHTSA’s study of automotive glazing trends. In this installment,
AGRR evaluates polycarbonates—a form of glazing that has the potential to revolutionize the glass industry—and looks at what NHTSA will do next.
The National Highway Transportation Safety Administration’s (NHTSA) search for an answer to the riddle of occupant ejection has gone beyond mere windshield glass. The agency is also studying the potential of other forms of glazing—primarily polycarbonates and bilaminates.
To many observers, polycarbonates are the future of automotive glazing. Not only do they have the potential to reduce the weight in automobiles, but they also can offer unlimited styling potential.
And, of course, there are the occupant retention issues that NHTSA is studying.
One company working to address these issues is Detroit-based Exatec. In 1998 Bayer AG and GE Plastics developed Exatec to make mass-produced polycarbonate windows a reality.
Polycarbonates weigh less than glass, making it possible for them to reduce the weight in an automobile significantly, thus increasing gas mileage.
There is “a 40-50-percent weight-savings versus glass … lowering the vehicle center of gravity, further systems weight reduction (i.e., liftgate and door assemblies), and improved assembly ergonomics,” said James Staargard, marketing manager for Exatec.
Increasing Style Options
The styling possibilities with plastic would also give automotive engineers many more design options than they currently have, according to Staargard.
“Complex 3D shapes are easily accomplished, where glass has been a limiting factor historically. Also, due to the engineering thermoplastic properties of polycarbonate, multiple parts can be integrated to achieve a more modular glazing solution resulting in lowering the systems cost,” Staargard said.
However, most of those interviewed for this article said the technology is still over the horizon.
Some critics claim polycarbonates have higher head-impact values. However, these are not a major concern for NHTSA. “While polycarbonates had the highest head impact values, they were still well below the likelihood of injury levels,” said Steve Summers, an engineer with NHTSA.
Another hurdle is the structural stability of polycarbonates: are they stiff enough, or does stiffness even matter as much as thickness does? This issue can be addressed by placing polycarbonates in areas where their stiffness is less of a factor or by increasing their thickness, according to some industry insiders. However, increased thickness means increased weight, effectively negating one of their advantages over glass.
Staargard has another answer to this issue.
“While polycarbonate does have a lower modulus than glass, the injection moulding process allows for localized stiffening of the part,” he said. “Along with utilizing curvature we have been able to demonstrate adequate stiffness for a wide variety of designs.”
Also, the issues of yellowing and abrasion still exist, though Staargard says these problems have been addressed adequately.
“Exatec’s proprietary plasma coating has resolved the abrasion issue and achieved Taber abrasion levels of less than 2-percent haze validated by several glass companies,” he said.
One of NHTSA’s main issues with polycarbonates is sharding. While glass breaks into tiny pieces, NHTSA is trying to determine how polycarbonates break when they are broken.
“We don’t know what they do and we don’t know if they don’t break,” Summers said. “We don’t really have a good test for sharding. Until we get more research, we are not allowing rigid plastics—except in limited areas.”
In spite of these concerns, plastics still have long-range potential to be a viable solution in automobiles. “Plastics is a rapidly-evolving field,” Summers said.
“If we could find a plastic that did not brade, that you could grab around the periphery, and that had protection equivalent to curved tempered glass, I would be very much encouraged,” said C. Thomas Terry, director of safety affairs and regulations for General Motors of Detroit.
Yet Another Option
While trilaminates and polycarbonates dominate the talk of alternative glazings, the third option—bilaminates—receives scant mention.
“We are testing them to be sure that we evaluate the full range of materials that are being used or may be used in the future for passenger car side windows,” Summers said. “Government regulations try to avoid specifying materials, and stick to performance criteria. Thus, it is preferable for us to test all likely materials and provide information to the manufacturers so that they can make informed decisions.” A bilaminate sidelite has a piece of glass on the outside to weather the elements and a layer of plastic on the inside. While the glass protects the plastic from the occasional rock or tree limb from the outside, there are other things it can’t stop—namely an accidental scratch from someone on the inside. “A person can hit it with their ring and scratch it,” said Glenn Davis, marketing manager for PPG Industries in Pittsburgh.
Where to Now?
As NHTSA continues to evaluate various types of side ejection prevention devices, some members of the glass industry have become anxious for the agency to issue a mandate to car manufacturers.
Both glassmakers and PVB-makers have begun a campaign to impress the benefits of laminated sidelites upon the public through the Enhanced Protective Glass (EPG) Automotive Association—a coalition designed to inform the public of the benefits of protective glazing.
However, some members of this group are also strongly encouraging NHTSA to mandate laminated side glazing. Included among this group is St. Louis-based Solutia Inc.
“I want to help save lives,” said Robert Esposito, manager of automotive product development for Solutia, explaining his company’s stand. “Some 8,000 fatalities per year in the United States continue to be caused by ejection. EPG technology is available commercially today. By NHTSA’s own estimate, this technology would save 1,300 lives per year.”
While PVB-makers would profit from replacing tempered glass sidelites with a laminated glass that contains their plastic, glassmakers would also benefit.
“There is a lot of opportunity for us to add value through sidelites,” Davis said.
“Right now we are trying to get some pull with the auto manufacturers [to put laminated sidelites in vehicles].”
|Back to the Future:
Auto Glass Techs
Have Seen Laminated Sidelites Before
|While alternative side glazing may be one of the newest innovations the auto glass and repair technician has to deal with, it really is not that new.
Technicians who worked on cars in the 1950s were well-acquainted with laminated sidelites. But tempered sidelites soon took over, limiting laminated glass to windshields.
Now occupant retention and safety concerns have pushed laminated glass back into sidelites.
Many technicians interviewed for this article had yet to deal with laminated sidelites, because they are now limited to higher-end cars such as BMW and Volvo. But the ones who did had mixed reactions.
Brad May, a supervisor with Klein-Dickert Co. in Green Bay, Wis., says one of the nice features of laminated glass is that it sticks together when broken.
“When they [laminated sidelites are broken] you don’t have all that glass rattling around inside the door and sticking to the grease,” he said. “It makes cleanup a lot easier.”
Mounting the window to the door may also be different, say some glass dealers, but it won’t force major changes. They say the laminated glass will not be bolted into the door, like tempered, but instead will be placed into tracks inside the door. In some cases, the laminated glass will also be wider.
While it is possible the auto glass technician’s job will be easier with laminated sidelites, there could be some negative ramifications as well, including the auto glass industry’s favorite word—liability.
Laminated glass could be installed into cars to prevent occupants from being ejected and this would put a different kind of pressure on the auto glass installer, said one industry insider who declined to be identified for this story.
“Now we will talk about this as a safety issue,” said the insider.
And, by doing this, the technician could suddenly face liability if one if their customers is ejected during a rollover—much like he would if a windshield gave out.
However, the advent of sidelites with an interlayer similar to windshields could change this.
“I would think that laminated sidelites would present new opportunity for the windshield repair community,” said Dave Taylor, secretary/treasurer of Cindy Rowe Auto Glass in Harrisburg, Pa., and president of the National Windshield Repair Association.
Further adding to the appeal of repairing laminated sidelites is their cost. They are currently estimated to cost anywhere from $20 to $50 more than the average sidelite. “They are very pricey,” said Walt Gorman, owner of A-1 Windshield Doctor in Seekonk, Mass. “We get many calls during weekends and Monday mornings for side window replacements because of auto break-ins.”
However, not all in the industry are of this opinion. Dave Shores of Glas-Weld Systems in Bend, Ore., points out that laminated glass is already on the side of some vehicles and it does not generate a large number of additional repairs.
“I don’t think that laminated sidelites are going to have much effect on the repair industry,” he said. “Busses currently have laminated sidelites and we repair a small number of them. I don’t see sidelites in cars being a higher percentage than that of the busses.”
Paul Syfko with Glass Medic in Columbus, Ohio, agreed.
“It will not be a big deal because there is not that much damage on sidelites from stones,” he said. “And in smash-and-grab situations the laminate will be fixable.”
However, with high-tech gadgets like stereo systems and global positioning systems, glass and PVB-makers have to wait in line to get their product in cars, according to Davis.
This leaves NHTSA as their main avenue from trilaminate sidelites. “If NHTSA would mandate it [trilaminate sidelites], we would not object,” he said.
On the other side of the fence is the General Motors Corp., which is urging NHTSA to evaluate other products such as side airbags before it mandates trilaminates. Terry, relying on his arguments of the additional strain occupant retention windows will put on doors and the unknown side effects of putting laminated glazing in windows, says it will be best for NHTSA to proceed cautiously.
“Given what we know today, I think it would be premature to require these types of things [laminated side glazing],” he said.
As further evidence of the cold feet General Motors has about laminated glass in automobiles, Terry has asked NHTSA if it mandates trilaminate sidelites, to essentially give the company three extra years to roll out vehicles with laminated windows.
“We want to get a sample out there and assure ourselves there is not a misbenefit before we make the commitment [to trilaminates sidelites],” Terry said.
In the middle of these two opposing forces is NHTSA.
In a recent report the agency declined to mandate laminated side glazing, essentially saying that it needed more time to test side airbags to see if they offer the same benefit as laminated glazing.
So far the agency has done lots of crash tests and developed a procedure for evaluating occupant retention among various types of glazing. However, it has not developed a test to properly gauge the effectiveness of side airbags.
This leaves NHTSA with a choice: it can mandate laminated glazing with the option of making changes once it has properly evaluated side airbags or it can do nothing and wait for testing of side airbags.
So far, it has chosen to wade out more testing before it decides whether or not to issue a mandate. This will probably be the agency’s approach until it is issued an edict from Congress.
Until then, NHTSA expects to continue what it has been doing.
“We owe it to society to do a thorough evaluation [of ways of reducing side ejections] and to determine what it means,” Summers said.
Leslie Shaver is a contributing editor to AGRR magazine.
Laminated Glass, Front and Sides: Get Ready for
the Newest Development in Adding Value to Automotive Glass
by Marcel Bally
There is a new way to add value to automotive glass, and it is becoming increasingly important. As you may know, many European luxury cars today feature coated and laminated sidelites, as well as coated windshields and this trend will inevitably spread to the rest of the world and eventually also down to more modestly-priced vehicles.
However, in other, and more fortunate, neighborhoods, comfort concerns such as avoiding solar radiation burn on the skin of the occupants and reducing the outside noise, are more important. For this market radiation reflective coating, similar to the low-E sputter- or “soft” coating on architectural glass, is the answer. This coating, consisting of several layers including metals such as silver, is a delicate surface and it cannot be applied unprotected to the outside of the glass. Therefore, the sidelites need to be laminated, similar to windshields, with the coating on the No 2 or 3 surface of the unit. Further, laminated sidelites represent a good noise isolation, and of course there is the protection against smashing-in the lite at the first blow. The logic of coating sidelites as protection against heat radiation applies of course even more so for windshields.
Laminated sidelites are increasingly requested for safety concerns. Coated laminated glass, sidelites, as well as windshields, offers enhanced occupant comfort and a reduced load on the air conditioning system as a side effect.
The coated surface can be damaged easily. That surface should not be touched during the entire process, and the equipment must be designed so that the glass is only handled from below. Where the glass absolutely has to be held from the top, the material of the touching tool must be selected with extreme care and any rotation or tilt movement is not permissible.
Even though the coating is microscopically thin, it permits migration of contamination. Therefore, the coating must be removed in the edge zone, so the laminate will form a lasting seal, otherwise the unit would delaminate long before the warranty expires.
And, of course, by design, coated glass shields against radiation. However, one of the consequences is that the increasingly popular automatic toll-paying devices installed behind the windshield (E-Z Pass for you New Yorkers) do not work due to the metal layer in the coating. For the toll-payers to work, a “window” in the coating of the windshield must be removed.
A loading system, picking glass one at a time from a rack and depositing it on a horizontal conveyor, only touching and handling the glass only from the uncoated underside. In case of a windshield line a station where the “window” in the coating for the toll-paying device is ground off. The material of the grinding wheel is comparable to a hard ink-eraser.
A station where the contour of the final part is being ground off. In theory, the above two grinding operations could be performed on one station. However, the resulting long cycle time would force too slow a pace on the entire line.
A station (or several stations) where the contour is scored and the trim broken off. Note that the grinding-off of the coating, or the “edge deletion,” must be performed before scoring the shape, otherwise the cutting oil would mess up the grinding wheel.
A station where the broken off edge of the glass is being ground. Modern bending processes for windshields require a No. 1 “pencil” edge to improve the yield in the bending oven. Sidelites need to have a No. 1 ground edge anyway.
All these process phases are CN- controlled and require highly accurate transfers from one station to the next, and high repeat accuracies for the processes themselves. Typical accuracy requirements for edge deletion and cutting are ±.08 in. (±.2mm), and for grinding, i.e. the size of the finished part, ±.04 in. (±.1mm).
Subsequent process stations include a washing machine with special soft-bristle brushes to clean the coated glass, and the bending and laminating equipment similar to laminating lines as traditionally used for windshields.
At present, and due to the still limited application of this technology, only fabricating centers of the vertically-integrated primaries process coated, laminated glass.
So, the next time you go to Europe, look at the more expensive cars one of the large Mercedes, for example, or even at a Renault, and check out the windshield. Perhaps you may be able to make out the toll-payer window somewhere above the rearview mirror. Check also to see if the sidelites are laminated, as one does not necessarily go with the other. Or, should you drive in an up-scale European car at home, you may find that the E-Z Pass, mounted at the top left corner of your windshield, does not work.
And then you may wonder: how long it will be, before your business will have to think about how to fabricate coated, laminated glass? Now you already know how.
Want More Info?
If you would like more information about what the National Highway Transportation Safety Administration is doing with alternative glazing, visit their website at http://www.nhtsa.dot.gov. The site has a search function allowing the user to type in words such as “alternative glazings” and find information.
To understand many of the issues from the glass, automotive and plastic manufacturer perspective, as well as that of highway safety advocates, visit http://www.dms.dot.gov. If you press the search button and type in “7066” as the docket number, you can find valuable comments about the laminated sidelite program.