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 Flattening Warped Plastic Sheet
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PAL

Posted - 2011 August 09 :  10:57:54 PM  Show Profile
Anyone know how to re-flatten plastic sheet?

Some months ago I used rubber cement to tack some Evergreen plastic sheet (with the "sidewalk" scribing) to basswood to use as a platform and portable base for a depot model. The sheet was painted with Polly Scale on top and tacked with rubber cement on the otherside to the basewood. I then set the model aside. Now the platform sheet is warped badly (at least an eighth-inch in the middle of a 12 x 6 inch sheet. I think it was the probably the rubber cement that did this. It's been in air conditioned luxury the whole time, and no lamps nearby, so it's not been heat that did it.

Appreciate any ideas, otherwise I guess I go buy more plastic sheet and start over -- in which case what would be a better glue to use?
Regards,
Paul

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peteski

Posted - 2011 August 09 :  11:32:51 PM  Show Profile
Yes, the rubber cement is the culprit. I have never found a good way to satisfactorily fix this warpage on a model, besides replacing the entire sheet (and using different type of a glue - like water-based contact cement, epoxy or CA glue).

Peteski

Country: USA | Posts: 3324 Go to Top of Page

randgust

Posted - 2011 August 10 :  10:37:09 AM  Show Profile  Visit randgust's Homepage
Yeah, anything with a petroleum-based solvent in it tends to have nasty side effects with styrene. I've had HORRIBLE things happening when laminating up styrene with almost any solvent-type glue. And most times it doesn't show up until long afterward, sometimes a year or more. Oddly enough, what usually happens is that it warps UP, not DOWN, meaning the solvent glues expand the styrene, not contract it.

I'm now doing the solvents extremely sparingly on lamination-type joints of any distance and thin material. I'm also using ACC to laminate rather than solvents, it doesn't have the problem at all and seems to be stronger as well.



Santa Fe Albuquerque Third District in N
Man is a tool-using animal. Without tools he is nothing,
with tools he is all. Thomas Carlyle (1795 - 1881)


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GOLDENSPIKE

Posted - 2011 August 10 :  5:08:11 PM  Show Profile
I tried to make a wood interior for for a micro trains box car by gluing in balsa wood and it ended up putting cracks in the car sides.

It has something to do with glueing wood to thin plastic.


Ron S.
"How many model trains is enough ??...a few more."
(a take on a J.D. Rockafeller quote.)

Country: USA | Posts: 1252 Go to Top of Page

pnolan48

Posted - 2011 August 10 :  9:28:41 PM  Show Profile
I,too, have never found a good way to flatten a sheet that has been warped by solvents.

I buy styrene in 4' x 8' sheets for about $20. They come rolled in a cylinder of about 12" diameter (by 4'). Often they stay rolled up for a year or so. I can relieve that kind of physical "set" by rolling it tightly in the opposite direction, or working it over a roller, again in the opposite direction.

Because I'm mostly building ships, I actually like the curve. And, when laminating thin sheets to form a hull, I like the increase in the curve caused by solvents.

Also found my latest sheets were actually 50" x 100." I presume this is to give some margin for damaged edges? Sure made a mess of my latest batch of cutting. I cut sheets into 10" x 16" sheets for normal use on a digital cutter. After cutting crosswise at 10" for a supposedly 48" sheet, I mark off 16" from one end and use a carpenter's square; then 16" from the other end. That way I'm sure to have too very square and smooth edges (the outside edges), and perhaps two edges on the middle piece that aren't so square and smooth. Except the middle piece was now 18" long. No big deal--except I was wondering why that middle sheet had an extra 2" on one end and didn't eject completely.

I'm testing the manufacture of some N-scale ships of moderate size.



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PAL

Posted - 2011 August 10 :  9:33:18 PM  Show Profile
Well, thanks for the replies; I regret that I am not alone in this experience.

So, off to the hobby shop Saturday to replenish my supply of the plastic sheet. Maybe I'll try carpenter's wood glue this time.



Regards,
Paul

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peteski

Posted - 2011 August 10 :  10:02:40 PM  Show Profile
Wood glue works on porous materials and doesn't bond styrene well.
I would suggest one of the adhesives I recommended in my original post.


Peteski

Country: USA | Posts: 3324 Go to Top of Page

PAL

Posted - 2011 August 10 :  11:09:01 PM  Show Profile
quote:
Originally posted by peteski

Wood glue works on porous materials and doesn't bond styrene well.
I would suggest one of the adhesives I recommended in my original post.


Hi, Peteski....I probably need something with a little "give" so if the wood base flexes a litte it will still remain bonded to the plastic, which probably deforms a little differently. What is "water-based contact cement"? Any brand names I'd recognize or be able to find easily?


Regards,
Paul

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randgust

Posted - 2011 August 11 :  06:47:41 AM  Show Profile  Visit randgust's Homepage
I've used five-minute epoxy - the two-part stuff - with great results to put brick plastic sheeting (H&R) laminated to both basswood and strathmore. Standard procedure now.

ATSF had a nasty habit of putting down brick platforms and then ripping up the edges for tie replacements, then 'fixing' the damage by repaving with asphalt. Simulating that with mating a layer of brick up against a layer of strathmore, and laminating that to a base has been the problem. The "La Posada" platforms were all done this way.

These have been down for four years.
http://gustafson.home.westpa.net/LPsite42.jpg

They are flat enough that some of the more inaccessible ones under the bridge are not secured, they just lay there, and haven't even warped in that situation.

If I were doing plastic-to-plastic I'd still use ACC. Plastic to wood-based gets the epoxy.



Santa Fe Albuquerque Third District in N
Man is a tool-using animal. Without tools he is nothing,
with tools he is all. Thomas Carlyle (1795 - 1881)


Edited by - randgust on 2011 August 11 07:00:33 AM

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peteski

Posted - 2011 August 11 :  6:54:02 PM  Show Profile
quote:
Originally posted by PAL


Hi, Peteski....I probably need something with a little "give" so if the wood base flexes a litte it will still remain bonded to the plastic, which probably deforms a little differently. What is "water-based contact cement"? Any brand names I'd recognize or be able to find easily?



PAL, here are some examples:
Dap 25336 Non Flammable Contact Cement Tan
Tanners Bond Water-Based Contact Cement
Titebond® GREENchoice™ Neoprene Plus Contact Cement
IIRC, Borden also produced this type of contact cement.
Google for these names and you'll find more info.

Personally, I prefer 5-minute epoxy for wood to styrene joints. Epoxy is flexible enough not to crack.


Peteski

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pnolan48

Posted - 2011 August 11 :  9:52:58 PM  Show Profile
Here's another idea: glue the plastic to both sides of the wood. Furniture makers (and many other industries that use laminates) always use a layer on either side of the core.

Now, scribed styrene (actually any sheets of styrene) at a LHS is costly, so I doubt you'd want to glue both sides with scribed or molded materials. If you can get an equivalent material of similar thickness that is cheaper, that would do the trick.

I have done this technique about a few dozen times for projects large (2 x 8 feet) and small, and never had a failure or significant warpage.

The old adage of always using odd number of plies applies here.



Edited by - pnolan48 on 2011 August 11 9:54:27 PM

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PAL

Posted - 2011 August 12 :  5:17:06 PM  Show Profile
Epoxy it is. Since I really don't have anything to lose by trying, I cleaned the contact cement from the back of the plastic, flipped the basswood over, and epoxied them together. The whole thing is now curing on a flat surface under a load of bricks. We'll see how that works. It not, I guess I buy more plastic and start over.



Regards,
Paul

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