Related: Automotive Materials
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.
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).
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.