Ink Flaking from Corrugated plastic

[Luke Sellers]

Hello,

We are experiencing [HASHTAG]#inkflaking[/HASHTAG] problems on our corrugated plastic prints. We print direct to surface on opaque corrugated plastic, intepro and coroplast brand, although I believe they are one in the same now. We use either a Mimaki JFX-500 or JFX-200 and we also have a megacoat XL UV liquid laminator which we use right after printing the signs. We have also experienced this problem with signs that have not been UV coated with the liquid laminator from several years back. The sign is so indestructable right after this process that it is unbelievable that it could flake off the way that it is. We also print direct to .040" aluminum and .080" digitially receptive styrene and have not had any complaints about them. 6 months seems to be about the amount of time it takes to see the problem developing. Testing is very difficult because the signs leave our shop looking and performing great. I'm attaching just a few of the photos of the problem that we have encountered.
Mainly looking for answers but anyone who is experiencing this problem I would love some feedback.

 

[Gino]

How many passes are you using ??

 

[Luke Sellers]

8 pass, Unidirectional

 

[theyllek]

We had this happen several years back on a Jeti 3150. We were using 3rd party inks and they did NOT stick to coroplast. Oh it left the shop looking amazing, but customers were bringing back signs on coro where the ink peeled off like in your photos. We didn't use that ink very long before switching back to OEM. I would say it's possible you've gotten an iffy batch of coroplast, or bad batch of ink ? Older coroplast leaks the plasticizers to the surface and can cause adheision issues.

 

[Luke Sellers]

We are using OEM LUS-150 inks on both machines. We have contacted Mimaki and they know of no problems. This has been happening for about 5 years, I suspect a lot without us knowing as it takes a customer complaint to notice and I suspect a lot of customers just go elsewhere and say nothing. We have used coroplast brand and intepro brand plus a few other types here and there( I know this is not helpful). Our signs don't just leave the shop looking amazing, you can't even scratch the ink off with a blade. The UV coating is rock hard after short term testing in our outdoors around the shop, we have found that it holds up outstandingly. Something changes about 6 months down the road. I suspect Expansion and contraction but this would mean that all corrugated should be having this problem and I can't find any other shops that have such a large problem as ours and we all buy from the same places.

 

[Gino]

On the real estate sign, why is the side we can hardly see looking fairly decent vs. the side you're showing us, isn't ?? That doesn't sound like an ink or substrate problem, but perhaps a prepping problem.Sometimes, when buying stock, the corona on them goes away, from what I understand in as little as 2 or 3 weeks, so if you have old Cor-X setting around, there might not be any left on it. Also, we were told years ago to use 91% isopropyl to wipe it down and keep rubbing til it's dry. Do not let it air dry, as that does more harm than good.

 

[Luke Sellers]

The reason the real estate one looks good on one side is because about 3 months ago that side was the only one that was flaking. SO we printed a panel and put it on top of the old one. Now we are dealing with all the rest of the signs at that site.
We use 91% iso alcohol to wipe down ALL signs no matter the material, and we wipe until evaporated. Again, adhesion issues at the outset is not our problem but good observations.
As a side note. We order corrugated by the pallet load and it does not sit around. We go through a pallet in 3 weeks.

 

[GaSouthpaw]

And it's completely possible you might need to use an adhesion promoter- whether you have initial adhesion problems or not.

 

[Luke Sellers]

And it's completely possible you might need to use an adhesion promoter- whether you have initial adhesion problems or not.

What is an adhesion promoter in this case? And what is the reasoning for it if the only thing that removes the ink after printing is a razor blade? I'm in chemist/ research mode so I'm pursuing all avenues. Thanks for the info.

 

[Gino]

If you want chemical evaluations you are definitely in the wrong forum. The best you're gonna get is personal experiences or lessons learned through others.

Anyway, your initial ink going down needs to adhere and bite in properly and if it's not, it's never gonna cure properly. Regardless of what's going on on top, the first band needs to adhere 100% and yours is not doing it. Otherwise, it wouldn't be lifting after a few weeks or months. Seems your solid areas are more problems then your gradient areas. Perhaps, your lamps need to be at a lesser density. Maybe lamp one at 1/2 power and the follow up at full or vice versa. Are you sure you've been using the correct profile. It's not a one fits all set up. We have several profiles to get the exact same color on various substrates.
We had one sign which was on Cor-X about 8 or 9 years ago, It was 6' tall and I believe 32 long. That's 8 panels long. Some... the ink worked fine and others didn't and we got all the substrate at the same time, cleaned it properly and redid the bad ones and within a year, they flaked off, again. We ended up replacing it two times. Our next thing was to never promise Cor-X for more then 8 to 12 months. It's temporary and the cheapest stuff on the market, so ya want cheap, ya don't get longevity. Over the years we've had maybe a dozen or so ACM products kinda fail, but that I blame on the vendors. I cannot help if they're buying this cheap sh!t from China and giving me the bottom of the barrel. Therefore, I buy from a select few places and no longer have the problem in over 5 or 6 years.

edit : Oh yeah, we also buy a specialized lamp which seems to be working better on Cor-X. A slightly shorter life-span, but who cares ?? When a machine is knocking out $1,000's a day, what's a little extra for a lamp really worth ??​

 

[GaSouthpaw]

Some surfaces (plastics like coroplast, some PVCs- unless you pay extra for "digital ready" or whatever they're calling it now- and even some paints, for instance) aren't suitable for the ink to "grab" the surface of and hold on. The adhesion promoters act much like 3M's adhesion promoter for vinyl installs- providing extra "bite" for the inks (not a clue what the chemical process is). You can usually get them from the same place you get your inks.

 

[bigben]

I don't own a flatbed or uv coater, but some shop around here run the material in the uv coater BEFORE and AFTER the printing. They told me the uv coating adhere better than the ink to the coroplast and the ink adhere perfectly to the coated layer. And I never saw them clean the coroplast before running it in the uv coater. It maybe worth a try...

 

[Gino]

Interesting.

 

[Bly]

I know it's concerning to have customers complaining about failures but corrugated plastic signs are really a budget short term option.
If they are getting 5 or 6 months I'd say it's time to buy some new ones.

 

[oldgoatroper]

The reason the real estate one looks good on one side is because about 3 months ago that side was the only one that was flaking. SO we printed a panel and put it on top of the old one. Now we are dealing with all the rest of the signs at that site.
We use 91% iso alcohol to wipe down ALL signs no matter the material, and we wipe until evaporated. Again, adhesion issues at the outset is not our problem but good observations.
As a side note. We order corrugated by the pallet load and it does not sit around. We go through a pallet in 3 weeks.

Sounds good, but maybe you might try using 99%, instead, though I'm not really sure that'd make much of a difference... I used nothing but 99% for 10 years or so on coroplast printed on UV printers, without any problems. Only had ink come off (right in the shop) once, but that was a UV light replacement fix.

I'd also check the expiry date on the ink, though I have also used ink beyond its expiry without issues (that I know of)...

 

[Luke Sellers]

bigben Unfortunately the Clear coat fails miserably just like this ink does. My thinking today is that we will be putting a life span notice on all our corrugated plastic signs. BUT...we are switching to smooth digital coro made by Intepro as a test. Guess we will give that some time and see how it goes.

 

[Pagan]

We have mimaki jfx200 , we switch from cheap Coroplast to real Coroplast brand
Problems solved . We print Coroplast all day long.

 

[TimToad]

It could be any number of things, but like Gino suggested it could be your lamp density. It needs to match your profile and cure at the precise second of exposure, or the ink while initially looking great, hasn't chemically baked into the surface or fully cured.

Is it only happening on Coro? What about your other substrates?

We've never had anything like it happen, but I do notice that 91% alcohol has more water in it to make up the 9% difference and it takes longer to evaporate as we're wiping. We keep both 91% and 99% on hand and for quickey temporary signs like political yard signs and such, we use the cheaper 91%. Everything else gets 99%.

We use the Intepro UltraSmooth Digital on an old Gerber ION Solara and the coat is clean, smooth and tough as nail.

On ACM, we first use 91% alcohol which seems to lift the gunk that the liner leaves, then Advantage 190 Wax and Grease Remover for the prep clean.

 

[rjssigns]

What is the dyne level of the coro? Treated material is only good for maybe six months, and that's asking a lot.
New flatbed in the lab and we're learning all kinds of things. Like printing on cabinet grade maple veneer plywood.

 

[SignMeUpGraphics]

We print on corrugated plastic that has the corona treatment day printed on the pack. We don't get anything over ~6 weeks old now and prints stick as good as ink to paper.
As rjssigns said above, dyne levels need to be high enough for the inks to adhere:
http://www.vetaphone.com/technology/corona-treatment/