Acrylic outgassing... How long?

[Terremoto]

A few things I should note is that in the shop I used to work at where we had an ongoing problem we were using the Bayer polycarbonate that came on huge spools. The vinyl we were using was either Avery A9 translucent or 3M translucent. The 3M vinyl was better but still had a problem.

Never a problem when we used the same vinyl on Acrylite. Same guys laying down the vinyl as well!

For testing purposes we brought in a couple of sheets of Sabic Polymers Lexan - they acquired the license from GE. Same problem as the Bayer stuff that came on the big spools.

One curious thing - no matter whether it was Avery or 3M - certain colors seemed to be really problematic - black and red if I recall. Yellow seemed to stay down just fine. Puzzling, no?

It gets more puzzling! From time to time we would re-do a polycarbonate sign face. Sometimes the old vinyl would be stuck down perfect and sometimes it would show the severe bubbling. (No way of telling who's product it was though.)

We would peel the old stuff and clean it good with 95% ethanol - as per some product handling bulletin from Sabic. Believe me, while I was trying to figure out what was going on I read a ton of product handling bulletins from Sabic, 3M, Avery, and Bayer. Many of them made mention of "outgassing" using that very term. Call it whatever you want - obviously these companies are aware of the issue!

In any case..., we would lay down the new graphics. Everything fine for the first few days then the bubbling would show up - BUT - stuck down tighter than cat crap to an army blanket where the old vinyl used to be. The severe bubbling would go right up to the edge of where the old lettering was - where it would be stuck down tight without a bubble. The boss cut one sign face up that was showing this and sent a sample off to the companies in question.

Where I work now we use whoever's handling the cheapest polycarbonate on any given day and order it in on an as needed basis. As a rule we don't carry any in stock. When it comes in we strip off the protective sheet and slap down the Avery A9 translucent dry. Never a problem in more than a year I've been here.

One thing to note. Where I used to work we did a lot of painting. Here, none. Not sure if that had anything to do with it or not.

One thing I'ld like to make perfectly clear though. In all the testing we did we pretty much eliminated the vinyl installer as the problem - some of these guys had been sticking down vinyl for 20 years or more. I would say the phenomena we witnessed when we re-did the odd sign face pretty much confirmed that.

 

[Tiogy]

Poly Tanks

Okay - here's one issue we have. First, let me say that we have been installing vinyl for over 20 years and we have applied onto all kinds of surfaces and situations. I also have 15 years experience in auto-body refinishing and we apply a lot of reflective and gold foil onto fire apparatus and have been doing so successfully for many, many years but, one of the recent jobs involved applying a large reflective chevron on the back of a polyethylene water tank that had been painted about a month earlier.

A month or so after the application, we got the call that our reflective application was done improperly because there were lots of little air bubbles all over. I was real curious since I know my installer on that job has tons of experience with reflective and something was wrong with this picture. Upon inspection, I noted that some of the reflective was applied to stainless (painted with the same paint) at the same time using the same vinyl and yet there was not a single air bubble to be found on the painted stainless.

I removed the bubbled reflective, replaced with new and made note of the difference in material substrates. After some investigation, we found that the paint had been baked and should have been cured - no problem. I also noted that the paint had no signs of adhesion failure. I did the application myself to be sure that the customer was satisfied as they have trusted me for many years.

A month or so later, I received another call - same deal. I started asking around to some other local sign shops and they were seeing the same thing in some cases, bubbling of reflective and foils on poly tanks. Another odd thing is that this seems to be a somewhat isolated case for us as we have done quite a few painted poly tanks without issue. Why just this one? We just removed the reflective again and laid 2 pieces of chrome vinyl on the problem area to see if it would develop bubbles again with about 48 hours test time and nothing happened. So tomorrow, we will try again and see what happens but, this is a hard nut to crack and there doesn't seem to be a definitive answer anywhere.

I agree that we tend to be the scapegoats when these kind of things happen and believe me, I have made lots of application mistakes over the years as well as seen adhesive failures but, this is not one of those cases. Perhaps out-gassing is not the proper term but, there is absolutely something strange at work here.

 

[oldgoatroper]

The (obvious) culprit here would seem to be the combination of the specific type of paint and the poly.

 

[CES020]

There is virtually no moisture in freshly made and properly stored plastic sheets.

I'd have to disagree with that statement. We have never had the issue being mentioned here, but we do have lasers here and cut a fair amount of acrylic. I have seen many many times while cutting, it's blowing water out the other end of the sheet. Yes, it's water. Not liquid plastic, water. I've seen water droplets form on the top of the sheet while cutting too, yet there is no water in our dry air that we shoot through the cut.

For the laser, the material has to be flat or the beam goes out of focus and can cause some issues on certain jobs. We buy the same material all the time and it's made to be cut with the laser, yet it's not flat. I've spend many hours on the phone with the distributors and then finally the actual factory people to discuss why the material is not flat.

On this particular material, it's protected on one side. I was told that the plastics absorb humidity, by just sitting there, even if in a properly conditioned space. What was happening with our product was, when you peeled the protective liner off, it opened up that "fresh" side to the air and the moisture would try and get out or in, respectively, depending on the conditions, and it would cause the material to bow.

Their answer was for us to remove the liner and allow it to equalize for several days. There was a word for what they said it was, the comment was "plastics are hydro____________", which I can't recall what the last half of the word was, but it started with hydro. I cut a job yesterday, flat on a table, which I don't normally do (normally use a cutting grid), and when I lifted the material, it was soaking wet with water under the cut.

There's plenty of water in plastics.

 

[oldgoatroper]

I'd have to disagree with that statement. We have never had the issue being mentioned here, but we do have lasers here and cut a fair amount of acrylic. I have seen many many times while cutting, it's blowing water out the other end of the sheet. Yes, it's water. Not liquid plastic, water. I've seen water droplets form on the top of the sheet while cutting too, yet there is no water in our dry air that we shoot through the cut.

For the laser, the material has to be flat or the beam goes out of focus and can cause some issues on certain jobs. We buy the same material all the time and it's made to be cut with the laser, yet it's not flat. I've spend many hours on the phone with the distributors and then finally the actual factory people to discuss why the material is not flat.

On this particular material, it's protected on one side. I was told that the plastics absorb humidity, by just sitting there, even if in a properly conditioned space. What was happening with our product was, when you peeled the protective liner off, it opened up that "fresh" side to the air and the moisture would try and get out or in, respectively, depending on the conditions, and it would cause the material to bow.

Their answer was for us to remove the liner and allow it to equalize for several days. There was a word for what they said it was, the comment was "plastics are hydro____________", which I can't recall what the last half of the word was, but it started with hydro. I cut a job yesterday, flat on a table, which I don't normally do (normally use a cutting grid), and when I lifted the material, it was soaking wet with water under the cut.

There's plenty of water in plastics.

What was it? Acrylic or Polycarb or something else? Every plastic will have different hygroscopic tendencies.

 

[CES020]

Acrylics, not polycarb.

 

[signmeup]

I'd have to disagree with that statement. We have never had the issue being mentioned here, but we do have lasers here and cut a fair amount of acrylic. I have seen many many times while cutting, it's blowing water out the other end of the sheet. Yes, it's water. Not liquid plastic, water. I've seen water droplets form on the top of the sheet while cutting too, yet there is no water in our dry air that we shoot through the cut.

For the laser, the material has to be flat or the beam goes out of focus and can cause some issues on certain jobs. We buy the same material all the time and it's made to be cut with the laser, yet it's not flat. I've spend many hours on the phone with the distributors and then finally the actual factory people to discuss why the material is not flat.

On this particular material, it's protected on one side. I was told that the plastics absorb humidity, by just sitting there, even if in a properly conditioned space. What was happening with our product was, when you peeled the protective liner off, it opened up that "fresh" side to the air and the moisture would try and get out or in, respectively, depending on the conditions, and it would cause the material to bow.

Their answer was for us to remove the liner and allow it to equalize for several days. There was a word for what they said it was, the comment was "plastics are hydro____________", which I can't recall what the last half of the word was, but it started with hydro. I cut a job yesterday, flat on a table, which I don't normally do (normally use a cutting grid), and when I lifted the material, it was soaking wet with water under the cut.

There's plenty of water in plastics.

Happens with wood too. If you make a wood table top and only finish one side it will bow when the humidity changes. One side will give up or absorb moisture and expand or contract as the case may be. The term for materials that absorb moisture is hygroscopic.

Liquid water is not coming from your acrylic sheet. The surface of the plastic is below the dew point of the air that was heated by the laser. I've seen the same phenomena when welding steel with a gas torch... and there ain't no water in steel.

 

[GAC05]

"I've seen the same phenomena when welding steel with a gas torch... and there ain't no water in steel."
You sure that is just not sweat dripping off your nose?


wayne k
guam usa

we need to ask Fred for a smiley welding icon for 2012

 

[john1]

Just checked out 2 back lit signs i installed (2) 2.5x5' prints to about a week ago and they look flawless.

I call silliness on this outgassing.

 

[CES020]

Happens with wood too. If you make a wood table top and only finish one side it will bow when the humidity changes. One side will give up or absorb moisture and expand or contract as the case may be. The term for materials that absorb moisture is hygroscopic.

Liquid water is not coming from your acrylic sheet. The surface of the plastic is below the dew point of the air that was heated by the laser. I've seen the same phenomena when welding steel with a gas torch... and there ain't no water in steel.

I guess those plastics engineers that were the ones that told me all about it were clueless. Stupid plastics engineers that make plastic for a living.....

There's a BIG difference in plastics that absorb water and steel.

Come on down, I'll fire the laser up and show you. I'll also have my plastic distributors here so you can tell them how wrong they are.

 

[Westcoast Sign Guy]

This is the longest topic I've read as it pertains to plastic f*rts.

 

[signmeup]

I guess those plastics engineers that were the ones that told me all about it were clueless. Stupid plastics engineers that make plastic for a living.....

There's a BIG difference in plastics that absorb water and steel.

Come on down, I'll fire the laser up and show you. I'll also have my plastic distributors here so you can tell them how wrong they are.

You made no mention of engineers, plastic or otherwise in your post.
I agreed with your statement about plastics being hygroscopic. I described a similar situation that occurs in wood panels to further support your post... about the flatness issue.

You and your "plastic engineers" and plastic distributors are free to believe that acrylic plastic contains enough water to leak out when it's cut. You are also free to believe that the earth is flat and that the Easter Bunny is real. Me... I'm sticking with science and physics.