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Laminating or sealing layers of Glass or plastics NEED SOME Guidance


Ovalrace25
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OK-- Here I go-- NEW project! A Cadillac series 75 originally purchased by the DOJ for assignment in Sothern Ca. AND ordered as "bullet-proof" ------ So now the car was retired and parked out to ROT and it did exactly that. The doors are filled with a cement/fiber that after years trapping dust and water cause all the body panels to rust-- Yep, LOTS of panel work to do. The roof has a Kevlar type thick layer as does hood, trunk and gas tank.

Now as for the windows--- three layers of Poly carbonate (curved) and some kind of clear, flexible silicon? that seems to have been what held them together. The door windows do not operate- they are all fixed in place.

What I want to do is "restore" the windows... Each layer needs to be polished (with what?) then all three clamped together (HOW?) and then sealed -- (with what?) The windshield LOOKS like it started with the OEM safety glass, then the layers of poly attached over that...

The car will go to a private collection in Europe when done. They have a few "Presidential" Limo's there now, this will add to the collection. This one is a 1976 and has the Presidential flag holders in front fenders. I have the log book and original DOJ purchase request. OH-- Reminds me, WHERE can I get these flag holders and flags? How about the original style behind the grill red and blue lights?

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The interior flexible layers are polyvinyl butyral (PVB), marketed by DuPont as Butacite, for example. The three flat layers of glass or polycarbonate plastic are typically stacked together without the PVB and heat-formed to shape. The PVB layers are inserted and the assembly is put in a bag made of high-temperature resistant plastic, sealed with a kind of putty, and a vacuum pump-out port is inserted in the bag. The bag goes into an autoclave where it is heated and the pressure raised to about 150 psi while the vacuum port is being pumped to remove air bubbles. This isn't something to do at home. The multiple layers help to absorb the energy of bullets, etc. Getting PVB to bond to glass is easy; getting it to bond well, and bubble free, to polycarbonate is much harder. I think flexible polyurethane is used to bond to polycarbonate.

If the car is not really going back into service as an armored vehicle, why spend the money - a lot of it - to duplicate the windows when the effect of multiple layers cannot be seen? For a display vehicle, it would be more practical to have one thick piece of acrylic or polycarbonate formed to shape. Acrylic can be scratched a little more easily than polycarbonate, but is this a problem? Here's a link to a brochure that describes forming polycarbonate: http://www.curbellplastics.com/technical-resources/pdf/polycarbonate-fab-guide-makrolon.pdf. The same procedures can be used for the Lexan brand material.

You could also have someone bend up a single thickness of glass and temper it for safety. Try Googling "bent glass" for suppliers.

Getting side windows done shouldn't be too difficult, as they are either flat or have a cylindrical bend of constant radius (so they can usually go up and down). Having someone make a new windshield or back glass could be an expensive challenge. If you want real bullet-proof stuff, try here: http://www.lexgardlaminates.com/.

A 1976 Cadillac 75 from the movie "Judgment in Berlin":

post-47871-143142656166_thumb.jpg

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Gary, thanks for the information! It helps a lot! The car will be on a permanent display and not really driven except maybe to some kind of exhibition. Windows are all fixed-- But in showing the car and what the safety features are, the windows need to be "relatively" correct. My thoughts are to polish/clean what is here, remove the PVB and then lay the three pieces together and seal around the edges to keep dirt and water out. I suppose this idea will not work as a permanent fix, as the pieces expand and flex with use, the seal will be broken.

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Normally, the PVB or urethane is not removable, ever. Did the layers actually come apart? Are any of them glass? Why do you think the pieces are polycarbonate versus acrylic? Got any photos?

If you need to polish plastic, get one of those headlight restoration kits with polishing compound and a pad that goes on an electric drill or angle grinder. Go easy, because you can't polish it back on if you take off too much material. You might just start with a soft cotton cloth and some toothpaste or paint scratch removing liquid polish, then wash with Windex and wipe with a soft cotton cloth. Stay away from paper towels on plastic because they may scratch the plastic.

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