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what happened here Update-interesting finding

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what happened here Update-interesting finding
Posted by NVSRR on Sunday, August 2, 2020 7:41 PM

Update.  So thanks to a little light rain called Isaias.  I had the time to look closer at the warpped pieces.   All the red panels warpped.   I have a few panels not used in the scrap box.  Digging them out I found them to be warpped too.  They were painted. A couple were not.   No exposure to glue.  Something with that sheet of plastic they were cut from.  contaminated batch?  bad mix of styrene?  Unknown.  I will have to cut new panels from a new sheet.  The trim pieces being .10 by .20 and .30  They can be glued back down. 

 

 

I am thinking heat.  The paint is vallejo.  This is a scratchbuilt building.  .20 and .30  styrene are the warpped parts.  The glue is MEK.  It was fine the last time i looked 3 weeks ago.   Other scratch built structures are fine.  Any other possible reasons these pieces buckled?   I might be able to glue them back down.   it only happened in that corner of the building too.  At least from what I could see.  A check in the sunlight will reveal if more areas are affected. .   This building is not anywhere near complete.

https://live.staticflickr.com/65535/50182781602_049c5c9747_b.jpg

https://live.staticflickr.com/65535/50182781547_e1a3b61e35_b.jpg

Shane

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Posted by caldreamer on Sunday, August 2, 2020 8:29 PM

Did you reinforce the corners with L beams?  Just gluing the corners together may not supply enough structural support depending on the thickness of the walls.  .020 and .030 are not very thick.  I use .040 with reinforced corners..

    Ira

 

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Posted by doctorwayne on Sunday, August 2, 2020 10:25 PM

It's difficult to understand what I'm seeing, but the thin black strips with their centres lifted were not properly cemented along their entire length, only at their ends.  Heat can deform plastic, but would not separate fully-cemented parts.  Using MEK, or other solvent-type cements, makes the two plastic pieces into one, by dissolving/softening the mating surfaces, and when those surfaces re-harden, they have become one.
I'd guess likewise for the red pieces, with their centres lifted, too.

When I build large structures, I use sheet styrene that's .060" thick and reinforce the corners with .125"x.125" styrene strip, and also, on really large structures, use the same materials to build interior partitions to keep the structure's overall shape...

 

 

When modifying kit buildings, such as this one, where both long walls are used on the side visible from the aisle....

 

lots of interior bracing is necessary...

I don't have an interior photo of this one, but it's done in the same manner as the other ones...

Even small structures like these...

...need adequate bracing...

Wayne

 

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Posted by gmpullman on Sunday, August 2, 2020 11:16 PM

NVSRR
The glue is MEK.

Another possibility is that you are attempting to cement pre-painted pieces to likewise painted walls.

MEK and any type of solvent needs to react with the styrene. The paint will inhibit the "welding" process.

Possibly the MEK soaked in to the backs of the red pieces enough to eventually warp them.

I'd say you need to find an adhesive rather than a cement OR sand away enough of the paint for the MEK to do its job.

Good Luck, Ed

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Posted by hon30critter on Monday, August 3, 2020 12:00 AM

gmpullman
Another possibility is that you are attempting to cement pre-painted pieces to likewise painted walls.

My thoughts exactly.

Dave

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Posted by SeeYou190 on Monday, August 3, 2020 12:54 AM

I think Ed is onto it when I looked closely at your pictures.

MEK will not work properly on plastic that has been pre-painted with Vallejo paints. Superglue is the only thing that I know of that works on pieces painted with Vallejo paints.

-Kevin

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Posted by Overmod on Monday, August 3, 2020 6:01 AM

I concur with the experts.  You can readily see this is the result of a bond failure, just as if the separated strips had never had glue applied to them between corners.  But they remain attached in the corners despite considerable stress, so something 'worked better' there.

Solvent welding is not a 'bonding' technique, it's effectively true facilitated fusion welding, and any 'barrier layer' that is not actively dissolved during the time the agent is present wicked into the joint will prevent the fusion just as the 'chrome' plating in older styrene models could impair solvent bonding with 'airplane glue' or other now-taboo chemicals.

Scraping paint from the area is the 'other' way to fix this, but effective 'non-stick' clamping of the warped pieces either way is going to be a concern, even before we take up the issue of why the strips physically warped as they did.  I'm in the cyanoacrylate camp, using the edge of something like a #1 or #11 X-Acto blade held sideways to hold the strip clamped flat while the CA sets up the full length.  And then wait to see if other stresses don't preferentially pop any adhesion of paint film to underlying plastic, underneath a new CA bond from strip to 'paint'...

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Posted by NVSRR on Monday, August 3, 2020 6:19 AM

its not new construction.  Forgot to state  this phase was done in Febuary.  It has been sitting waiting for me to find designs to print for flooring and other pieces 

 


The plastic panel red pieces are warped.  But still glued on.      All the corners are re inforced.     I can understand the paint and mek. Those areas are taped before painting.    I noticed where it softened and sucked the paint under in a couple spots. But doesnt explain all of the pieces warping.   The red panels are actually warped. The main base sheet that makes up the building has a bow in it even though it is re inforced   I dodnt use any different proceedure in construction. Tape off glue areas, paint pieces, assemble.  Touch up.  

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Posted by Overmod on Monday, August 3, 2020 7:11 AM

Red has the same lack of bond as the thin black webs.  Did you make any test 'coupons' of these materials to confirm the MEK you were using is a suitable cosolvent for effective welding, and that it would not cause swelling of the plastic instead (which sure appears to be happening to make those pieces bow)?

If you remember the length you cut the pieces to, check them again and see how much dimensional change has occurred.See Wayne's note about lots and lots of orthogonal internal bracing and webs.  All that bowing force in the now-loose pieces will be absorbed in the face styrene once you rebond them with CA (or perhap more suitable solvent or 'polymer dissolved in solvent' a a mechanical glue), and I expect that will start new distortions -- be ready.

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Posted by NVSRR on Monday, August 3, 2020 7:35 AM

The red panels.  Are stood off the face by .20. Just as on the prototype building. There is a small  square of .20 styrene on the back.  That is the only contact point for those panels.  Although warpped. They are stuck on good. 

the mek is the same as used on other scratch built buildings   I would expect the reaction to occurr on those buildings as well if it is a reaction.

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Posted by rrebell on Monday, August 3, 2020 10:36 AM

I do not see complete bonding. Putting glue on one side to wick dose not always make it to the other side and on larger peices it evaporates before it can even get to the center at times. I have had to use old style tube glue before on larger peices and then wick glue the edges to get an effective bond.

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Posted by Lastspikemike on Monday, August 3, 2020 10:54 AM

My best guess is localized heat damage. You can see some warped parts are clearly longer now than when the glue set. Window frames are also warping, not just the panels. 

If so then the question is: how was localized heat applied only to those bits of your structure?

Adhesive failure cannot cause warping, only fail to restrain it.

It is possible for the solvent type cements to warp the side of the styrene it is applied to but that shouldn't cause warping to that extent. That much over cementing should cause visible damage. Removing one warped part will be diagnostic. Examine the now hidden side for signs of cement damage. If none then heat was the cause. 

Alyth Yard

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Posted by dknelson on Monday, August 3, 2020 12:11 PM

The damage reminds me of what happens when a gas emitting glue or cement like Walthers Goo is used in a tightly sealed structure or freight car body.  

This may sound kind of nuts but I recall that back when oil heat was more common than it is nowadays, guys reported problems with plastic - sheet and styrofoam - in the same room as the furnace and the thought was that imperfectly burned oil fumes were attacking the plastic, sort of an aerosol solvent.  

Dave Nelson

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Posted by NVSRR on Tuesday, August 4, 2020 5:55 PM

I only have a electric heat pump doing the heating and cooling for the. railroad building.   It is no where near the vents either

 

Shane

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A realist sees a frieght train

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Posted by fwright on Tuesday, August 18, 2020 11:34 AM

Another source of heat that has burned me at module exhibitions is sunshine through windows. That has caused soldered rails to "pop" and other calamities. And of course sunshine through glass had caused how many cracked vinyl/foam coverings in automobiles?

Besides heat, the off-gassing of the "blue" and "pink" foam for about 6 months after manufacture causes shrinkage of the material. Enough to bow plywood sides surrounding the foam to which it is glued. Or the glue gives way (usually the case with white glue). Similarly, many plastics off-gas when new, which may/may not cause shrinkage of the original plastic piece. The off-gassing can be verified in new autos in the fogged up windshields and the "new car" smell.

Finally, humidity changes can have a dramatic expansion/shrinkage effect on any wood products - which includes paper products. The fix is to either accommodate the expansion/contraction or to brace it firmly enough so that it can't happen.

just my experiences Fred W

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