Prepping / Cleaning Polycarbonate

[300mphGraphics]

Using brand new sheets of poly. Do you just remove the protection sheet from the manufacturer and letter, or do you prep it somehow? I've been removing the sheet and lettering, but have had a few hits and misses such as bubbling of the vinyl. Usually takes a couple days for the bubbles to show. Interesting that it has always happened with the black vinyl and not the translucent colors.

Thanks.

 

[J Hill Designs]

Using brand new sheets of poly. Do you just remove the protection sheet from the manufacturer and letter, or do you prep it somehow? I've been removing the sheet and lettering, but have had a few hits and misses such as bubbling of the vinyl. Usually takes a couple days for the bubbles to show. Interesting that it has always happened with the black vinyl and not the translucent colors.

Thanks.

just let it breathe a bit before lettering

 

[Gino]

Are you putting it down wet or dry ??

We always wipe it down with alcohol, whether it's translucent or digital media.

 

[Zac]

Alcohol is great, another product I've used is alcohol based and has anti-static properties called Plastic Prep from Matthews Paint. It's pretty amazing. As long as the bubbles aren't too high pressure they should go away after a day or two.

I will generally lay vinyl wet on lexan/poly, even just a mist of rapid-tac/homeade works wonders.

 

[300mphGraphics]

Putting it down dry.

Vinyl is flat after application and panel installation on site, and takes a day or two to appear.

Here's another project, this one mine. This the yellow trans went down solid and the black Oracal 651 went right over the top. North side of the side is fine, south side has bubbled like crazy. Kind of cool effect, 3D signage! This one has been up for 2 months with no reduction in bubble size.

 

[reQ]

Another thread about polycarb & it will be another debate between two camps lol.

Still holding to my opinion - You have to let it sit after you peel of the plastic (i usually leave it overnight)

Never had this issue after i started to allow to "outgas" before lettering, or however you wanna call it

 

[Gino]

Outgassing ?? No, it's not, that. How does outgassing differentiate between yellow vs. black or that red rule at the top ??

 

[J Hill Designs]

Outgassing ?? No, it's not, that. How does outgassing differentiate between yellow vs. black or that red rule at the top ??

outgassing argument aside, the black is opaque and the red/yellow are translucent, so there IS a differentiating factor

 

[300mphGraphics]

Sorry for starting another thread, I hate that.

In researching the topic before starting a new thread here I did find a list of compatible cleaning agents. Isopropanol is a no no (though I've never seen any issues) according to: http://www.polycarbonatestore.com/how-to-clean-polycarbonate-sheets/

 

[Billct2]

Dry app, differences are black being opaque, layered and it on;y happened on the south side. Maybe outgassing from the panel being heated by the sun is a possibility.

 

[Gino]

Sorry for starting another thread, I hate that.

In researching the topic before starting a new thread here I did find a list of compatible cleaning agents. Isopropanol is a no no (though I've never seen any issues) according to: http://www.polycarbonatestore.com/how-to-clean-polycarbonate-sheets/

They're also not talking about rigid 3/16" sign faces. They sell greenhouse supplies. Those are fluted poly pieces.

 

[JoeBoomer]

Outgassing

Lexan (polycarbonate) is supposed to outgas for 24 hours+ after you take the liner off of it. Just like you shouldn't laminate solvent-printed vinyl for 24 hours. Because we would NEVER laminate before it outgasses... Wait, we never wait for it to outgas. That's what I meant to say.


I may have shared that info, but I don't actually follow that. So, my post is pretty much useless at this point.


As you were....

 

[rmaclucy]

I'm confused...

I was always taught to never use alcohol on poly, it can craze. I always spray with water to help remove the static, dry and letter. Wet apply for
transluscent and dry for everything else.

 

[Gino]

By Jim Hingst.............

Painting Polycarbonate Sheet

The extraordinary clarity of polycarbonate makes it an excellent substrate for backlit signs. Generally, but not always, the sheet is sprayed on its second surface. Because the paint faces the inside of the sign cabinet, it is protected from the elements. Any painting done on the first surface of the sign face must be clear coated.
Paint Selection. In selecting a paint for painting polycarbonate sheet, follow the manufacturer’s recommendations. In thinning the painting, use the recommended solvents. Because solvents can craze or craze polycarbonate, use milder thinners.
As a rule of thumb, avoid using keytones, as well as chlorinated and aromatic solvents. Generally, paint systems based on aliphatic hydrocarbons, such as mineral spirits, alcohols, heptane and hextane, are compatible with polycarbonates.
Cumulative Stresses. Cracking and crazing are noticeable. But not all chemical damage is visible. Even if you cannot see a physical change to the sheet, the damage may already be done and can ultimately lead to failure when combined with mechanical stresses, both in fabrication and after the sign is installed. Stresses on plastic sheet are cumulative. One builds upon another, until you literally reach a breaking point.
Read & Heed. Before spray painting polycarbonate sheet, carefully read the manufacturer’s technical bulletin and follow their recommendations regarding surface preparation, approved solvents and paints, and spraying techniques. Two popular paint systems using in decorating polycarbonate are Lacryl® 400 made by the Spraylat Corporation and Grip-Flex® FR-2 from AKZO Coatings.
Test, Don’t Guess. Regardless of what type of substrate you are painting, before you use a new paint system, the best practice is to “TEST, DON’T GUESS”. Spray a few samples of the substrate with the paint system.
Adhesion Testing. After painting, check for good adhesion, using the tape test. After burnishing an aggressive tape, such as 3M Brand #600 clear tape, over the painted surface, quickly pull the tape and see if any paint comes off in the process.
Surface Preparation. Thorough cleaning to remove dust and other contaminants will ensure paint good adhesion. In prepping the surface, be sure to follow the specific recommendations of the paint manufacturer.
The right way to clean polycarbonate, is to first wipe the surface with a clean, damp rag or chamois. This will remove the static charge in the sheet and help clean any contamination from the sheet. The second step is to complete the cleaning, by wiping the substrate with a mixture of denatured or isopropyl alcohol and distilled water. The recommended ratio of alcohol to water varies from 25% alcohol and 75% distilled water to 50/50 alcohol and water.
Be very careful in using any solvent stronger than alcohol for cleaning. Strong solvents will subject plastic sheet to stresses that often result in crazing and cracking. If you need to clean a sheet, which has been stained by grease or oil, you can try a stronger solvent, such as naptha. If you must use strong solvent, allow the sheet to dry completely before painting.
Static. If you use the proper cleaning procedure, you should kill any static charge in the plastic. Like many other types of plastics, polycarbonate can build a static electric charge. Spray painting a surface with a static charge can result in a blotchy finish, which will stick out like the proverbial sore thumb, when the sign face is illuminated.
Sign makers use a couple different techniques to kill or neutralize the static charge. One common practice is to wipe the surface with a damp, lint-free rag. Others wipe the surface with an alcohol/water mixture.
Another practice is to kill the charge with an ionizing air gun. Do not use anti-static cleaners or dryer sheets, which can contaminant the substrate, potentially causing paint adhesion problems.
Spraying Technique. Spraying some test panels is also a good habit to get into, just to check whether the paint is thinned to the right viscosity or to check your air pressure settings are correct. As a general rule of thumb, you will want to use the lowest pressure possible, while still achieving the desired result.
In spray painting plastic sheet, you will want to apply very thin coatings. Applying heavy coatings, can result in either the paint sagging. Heavy applications of paint also result in a high concentration of solvent, which can craze the sheet.
Spraying a coating of paint, which is too thin, has its own set a problems. Dusting on the paint can result in a slight texture, which will give the paint finish a dull or matte appearance.
The technique that many professional painters use, when spraying, is to keep the nozzle of the spray gun about twelve inches from the surface.
In spraying, move the spray gun in a straight line from left to right (horizontally). You can also vary your spraying movement, by painting a coat vertically or from top to bottom. Varying the direction of the spraying motion, will ensure that you achieve a uniform coating of paint. Keep the rate at which you spray at a steady pace. Continue spraying until the pattern is off of the substrate. Never stop a spraying pass on the surface of the sheet.

 

[Techman]

Outgassing is a myth.
If there was outgassing why is it that no one has ever observed an outgassed liner? No one has .. ever. The liner is applied while the product is produced. The OEM doesn't wait days to "outgas" the plastic and then apply a liner. There is nothing ot outgas. The plastic is made via combining molecules that bond electrically. There is no solvent involved in the final production. It is thermal plastic.

Bubbling on one side? The sun heats the air trapped under the vinyl. Yes there is air trapped under the vinyl. It is compressed from the squeegee and later appears as blisters. Happens especially under layers.

Cleaning the panel? If there is a liner on it why is it dirty? How did the liner stick on it if it was contaminated?

Do we see any other industry cleaning those panels when in production? No, not one that I ever visited. There are no less than 7 companies here that use plastic sheeting and not one of them cleans a sheet before use. No one. They simply peel and go. They use plastic sheet by the spools full that come off train cars. Not one inch of it is ever cleaned before use. None of them are baked to "outgas" them or any other secret treatment.

I cleaned a panel and the rag was filled with some kind of sludge. That proves it needed to be cleaned.

"" ..

Some plastic is sprayed with a UV treatment. Using some "cleaner" removes that UV protection. So why spend extra to get it only to remove it? That sludge was the uv coating..

 

[signbrad]

It sounds like there have been some spirited polycarbonate discussions here in the past. Here's my two cents worth.


The bubbles that develop later are from trapped moisture


Polycarbonate does not outgas solvent fumes as do some other plastics as they cure, as Techman mentioned in his post. Or if it does outgas solvent, it's so small an amount as to be nondetectable. However, polycarbonate does absorb moisture, which is released as water vapor as the the plastic dries. Technically, you could call this "outgassing," but it is not how the term is commonly understood. How can this release of water vapor affect vinyl film? A technical brief from Covestro, the maker of Makrolon polycarbonate sheet, says, “Trapped moisture within the sheet often results in bubbling of vinyl film. Pre-drying sheet leads to a surface dryness conducive to good film adhesion.”
Of course, you may not have the equipment to flash dry polycarbonate sheets for one hour at 250 degrees as Covestro recommends. Laying a sheet out overnight in a warm room may be the only option for most of us. And I suspect that those who live in a dry climate rarely experience this bubble problem.


Here's a link to the tech sheet from Covestro. Covestro, since last year, is the name of a subsidiary of Bayer, and was formerly known as Bayer MaterialScience.

http://www.covestro.com/~/media/Pro...icas/MSC115_Technical Bulletin Outgassing.pdf


An alcohol wipe removes static

Regarding cleaning, it make sense that a sheet of polycarbonate should already be clean if it has been protected by a cover sheet. But, it may also be full of static. Plastic faces cannot be spray painted successfully without removing the static, and that is the primary purpose of the alcohol/water wipe. I was taught to mix two parts water to one part alcohol and wipe with a chamois leather (not a cloth).

Isopropanol is the least toxic of the commonly used alcohols and is always my choice, but I've used "denatured" when isopropanol was not available. Denatured alcohol is ethanol that has been made poisonous so that it can't be consumed (or taxed) like whisky. Methanol, the race car fuel, is the other readily available alcohol. But it is highly toxic and I don't use it.
The Plastic Prep sold by Matthews Paint is mostly an alcohol mix.

Another anti-static technique I use when painting plastic faces is to fill a squeeze bottle full of water and squirt it all over the back of a plastic sheet just before painting. This can help you get beautifully even translucent backgrounds, even in the problem colors. I learned that trick thanks to Paul Berkshire of Peoria in the late '70s.

Brad in Kansas City

 

[ams]

Never apply vinyl before prepping. Use Rapid Prep.