Advancing Glass
What do the windows of some of the hotels in Las Vegas (e.g., New York, New York)
have in common with your car?
Well, while there are probably a plentitude of answers (some of which have
to do with whether one’s vehicle will start on a cold morning being a crap
shoot), the one in question relates to the glass that’s used. That is,
just as the windshield in your car is a laminate, laminated windows are being
used in these buildings. One of the benefits of the laminated glass is, of course,
that when there’s a collision, the glass generally stays in place: it cracks,
but doesn’t shatter. The side glass, which is tempered glass, shatters
into thousands of pellets when it is struck with an object.
While there is certainly something to be said for using glass that doesn’t
shatter for casino hotels, a key reason why the laminates are used has to do
with aesthetics: The glass is colored. It looks good.
Which is why both Robert Esposito, manager, New Product Application, and Tom
Laboda, market development manager, both of Solutia Inc.’s Automotive operation,
think that laminated glass has a greater potential for vehicle applications.
While there is generally a lot of attention paid to the shape of sheet metal
and the coatings applied to it, they believe that there is the means by which
colored glass can play a bigger role in design differentiation. Solutia is not
a glass supplier. Rather, it produces the material, a polyvinyl butyral (PVB),
that is the interlayer between two sheets of glass to create the laminate.
Generally, the PVB interlayer is clear. Which still provides benefits. But
as Esposito notes, while most vehicle manufacturers use laminated glass only
for the windshield (which is a safety requirement), an increasing number of
builders—European marques, in particular (e.g., Porsche Cayenne, Volvo
XC90, Mercedes E-class, Audi A8)—are putting the laminated glass in other
areas.
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| THE LINCOLN AVIATOR-like
its bigger brethren, the Navigator-uses a laminated glass for the front
side windows. A key benefit: reduced noise, a characteristic that customers
associate with high-quality vehicles. |
For example, there is the front side glass that’s used on the new Lincoln
Aviator, a laminate produced by PPG Industries (Pittsburgh, PA). The material
is called “Safe and Sound.” The safe part relates to a comparison
with the tempered glass that’s ordinarily used in these applications. That
is, according to Ernest Hahn, PPG vice president, automotive glass, the PPG
windows take up to 20 times longer to penetrate than conventional glass: “It
takes only about a second to break conventional tempered glass.” Which
means that it provides a measurable amount of benefit vis-à-vis some
miscreant breaking into one’s Aviator. But the “Sound” part is
similarly interesting. Hahn states that there is a sound attenuation of up to
6 decibels with the glass on the Aviator. As vehicle manufacturers are looking
for the ways and means to decrease NVH, glass is clearly an aid. In the case
of the Aviator application, PPG was able to produce the laminated side windows
thin enough (<4 mm) to be used as a direct replacement for standard tempered
glass.
A benefit on the Aviator—as well as in all of the automotive applications
of laminated glass in place of tempered glass—is that the material is lighter.
The rule of thumb is that there can be a weight savings of 10 to 12%. In the
specific case of the Aviator, the weight save is nearly two pounds.
Of course, the weight save isn’t as important on a building as it is on
a vehicle. Which brings us back to the colored windows in the Vegas casinos.
That same sort of effect can be achieved for vehicles. Solutia’s Laboda
points out that at the 2003 North American International Auto Show, several
of the concept vehicles were fitted with colored laminated windows—wrapped
all around. Among them were the Pontiac G6, Cadillac Sixteen, and Mercury Messenger.
These concept applications can give way to production applications.
The first thing to know about nanomaterials is just what “nano” means.
It’s billionth, as in a billionth of a meter. Yet, generally speaking,
when someone is talking about “nanomaterials,” they aren’t referencing
things that are exceedingly tiny, but materials that have constituents that
are measured on a scale of a billionth of a meter. So, for example, when Peter
Maul, president of Nanocor Inc. (Arlington Heights, IL) discusses the nanoparticles
that his company provides, he describes a nanoclay (a smectite, for those who
are in the know about materials that were created some 60 million years ago,
volcanic ash that was deposited in such places as the inland sea that once covered
what is now Wyoming, Montana, South Dakota, and Utah), one that is a platelet,
or like a sheet of paper. But this sheet of paper isn’t your typical 8-1/2
x 11 sheet. Rather, it is on the order of 300 to 500 nm in length and width.
Its thickness is less than a nanometer—which is less than the wavelength
of light.
What’s all the more remarkable about this stuff is that Maul and Dave
Foell, R&D manager of PolyOne (Cleveland, OH), a compounder of various polymers
for applications including those in automotive, are talking about how these
tiny bits of clay can result in materials such as polyolefin and polyvinyl chloride
that are stronger and stiffer. Which, of course, seems counterintuitive: these
little particles resulting in stronger material? These nanocomposites (nanoparticles
in a polymer matrix) are being recommended for use to produce interior trim
items like door pillars, dash mats, dashboards, airbag covers, and the like.
Nanocor and PolyOne have recently formed a strategic alliance through which
they’ll be providing nanocomposite materials to molders.
The size matters. That is, according to Maul, when you use traditional filler
materials (e.g., glass, minerals), in order to get the kind of strength and
stiffness that is required for the application it is likely to be necessary
to use a dense amount of the filler. (And realize that these materials are of
a size that can be generally measured without the need of sophisticated lab
equipment.) This density can make processing with traditional processes (e.g.,
injection molding) rather difficult because the loaded material is going to
be resistant to flow. This has a consequence in terms of making sure that the
mold is entirely filled with the material. And Foell notes that if there is
supposed to be a texture on the part (think of the texture that’s typical
of a dash panel) or a smooth gloss finish, because of the viscosity of the material,
it may be difficult to replicate because it won’t (a) get to all of the
indentations in the mold surface or (b) won’t result in a smooth surface.
“The nanocomposite has the ability to flow easier and smoother,” Foell
explains.
He says there’s something else that sometimes happens when trying to get
the required robust physical properties with traditional filled materials: It
may be necessary to increase the gage of the part in order to get it. Which
results in a weight penalty. But deploying the surface modified montmorillonite
material (a.k.a., the tiny bits of clay) in the matrix means that the penalty
doesn’t occur.
Because there is an emphasis in this instance on interior components (others
are using nanocomposites for exterior parts, like for optional running boards
for the Chevy Astro and GMC Safari vans), there is another advantage cited by
Maul and Foell of the nanocomposites: fire retardence. Apparently, the same
sort of fire retardancy that is provided by the tiny inclusions can be attained
with conventional fillers but at a level where the filler accounts for as much
as 40 to 50% of the mix—which generally means a heavier component than
might be desirable.
One concern that non-users of nanocomposites may have when considering the
materials is whether they’ll need to have to invest in some ultra sophisticated
equipment in order to transform the polyolefin nanocomposite pellets into parts.
That’s not the case; conventional equipment can get the job done. (However,
compounding the materials is apparently tricky: it isn’t a matter of just
taking a polyolefin and tossing in a thimbleful of nanoclay).
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| Even if you're not traveling
in the desert, chances are you don't want to climb into a car that has
been sitting in the sun all day-unless there is a glass laminate that includes
a non-metallic solar reflecting film. (You could use a metallic film, but
it might interfere with your cell phone or telematics system.) The backlite
on the Porsche Cayenne makes use of a nonmetallic film from 3M. |
A COOL APPROACH
Automotive designers keep increasing the size of the glass on vehicles. Which
is turning them, in effect, into greenhouses. Which may be nice on a winter’s
day. But which means that there is a tremendous load on the HVAC system during
the summer—perhaps even in the spring and fall, too. This is not a trivial
problem. According to 3M, the temperature of a parked vehicle can be in excess
of 150°F (taking into account the heat load from the sheet metal, as well).
There is another phenomenon in vehicles. And that’s the loading of cars
and trucks with various electronics, like telematics services.
A way to at least ameliorate the increased glass/heat issue is to use a metallic
coating on the glazing. Which helps reflect sunlight. Which helps reduce the
heat in the passenger compartment. This is something that is being used by vehicle
manufacturers. But there is a problem. Which brings us to that second phenomenon:
electronics. The metallic coatings not only reflect sunlight, they can also
reflect electrical signals. So, one approach is to leave an uncoated space—up
to 10-in. diameter. Which is not only aesthetically marginal, but which allows
a hole for the sun to get in.
So, people at 3M’s Film and Light Management Laboratory got together with
people from the 3M Automotive Div. and set about to develop an alternative:
a non-metallic solar reflection system. This system is based on a film that
has hundreds of layers—but some of those layers are only several molecules
thick. The film is used in a five-layer laminate: (1) glass, (2) polyvinyl butyral,
(3) 3M film, (4) polyvinyl butyral, (5) glass. The film is color-free, so it
can be used with colored glass. Because it is metal-free, it doesn’t cause
interference.
Among the vehicles it is being used on are the BMW 7-Series and the Porsche
Cayenne, both backlite applications.
