Not possible to paint on polypropelene

Nice answer!

milo

Sparkstation is correct in his assessment of the polyprope issue.

I work for a printing company and we print on polyprope all the time.

We do have to purchase a specific material that has been treated and an ink that is specifically formulated to print on this type of material. It took a long time to sort this out with the different vendors we use. We are also curing the ink with High intensity UV light. This actually bonds the onto to the material.

You may have to work with a few people to get it sorted but it will likely be cheaper to have it outsourced as the equipment is quite expensive upon initial purchase.

Let me know if you need more information.

In addition, there may be a difference in flexibility between the polypropylene surface and the paint that is being applied to it. If the dried paint is more rigid, then when the polypropylene flexes, instead of flexing with it the paint will crack. It's a short step from there to it becoming disconnected from the polypropylene sub-surface.

Hi Guest,

I agree with Sparkstation 100%. I work in the coating / laminating industry and we laminate polyethylene, polypropylene, nylon, and polyester films. The polyethylene/polypropylene films must be corona-treated before we can get the adhesive to "stick" and hold. There is also supposedly a primer that will work called Prime-IT, manufactured by Ciba, though I have never used it.

Just some thoughts...

Mike

I am not sure if this will work for polypropylene, but when blowmolding companies make bottles of polyethylene, and want to screen print a label on the bottle, the surface is usually flame treated. I have seen fixtures where the bottle is quickly rotated past a low level flame comming from a manifold to surface treat the the bottle.

I too have seen polyethylene bottles come streaming at high speed through a large gas flame. They are not in the flame long enough to even get warm. But, this process allows them to be screen printed. I don't know if you can effectively treat polypropylene this way.

Hi Guest, I'm a painter and a year ago I was asked to paint a friends car battery holder to match his paint job on his car. After several trys to get paint to stick, I discovered the battery holder was made of polypropylene. I consulted with my rep from Sherwin Williams Paint and found their product called Preprite-Problock primer. Two spray coats of this water base primer and two coats of paint did the job. I still see this friend and the battrey holder still looks great. Since then I have used this primer on PVC pipes, wall laminate, galvanized metal, aluminum and old wall paneling with out a hitch. Just one word of worning, wear gloves, it sticks so well if you get it on your hands you'll be wearing it for a while. Hope this helps, Casey

My initial non-informed guess would be: have you tried the new Krylon paint made for plastics? I believe it is called "Fusion". It probably won't work either, but it is all I have found to paint some kinds of plastics, including old Tupperware bowls which have that "greasy" feel mentioned by another person here. The paint hasn't been on the plastics for very long so I don't know how well it will endure over time.

Follow the advice of the folks who knew what they were saying because of experience at work, etc. But it may not hurt to try the Fusion paint. It would be easier than the flame methods, if it worked.

Best of luck to you.

The "reason" the paint does not stick is because of the low surface tension. Pretreating the plastic with a corona treater, flamer or pretreating wipe (like isopropyl alcohol) changes the charge of the surface, thus making it more receptive to the paint or ink. A solvent-based ink is also more likely to create a chemical bond with the plastic's surface.

You can see this easily by dripping some water on a piece of plastic. If it beads up (like on a freshly waxed car) it has low surface tension. If the water "sheets" the plastic has high surface tension (compared to the water.)

Here's an article: http://www.padprintmachinery.com/InTheNews.cfm?id=25 on pretreating plastics and why plastics need pretreatment to create a chemical bond with inks.

Here's another one: http://www.padprintmachinery.com/InTheNews.cfm?id=27 that talks about ink adhesion and types of plastic, which was published in the July 2007 Injection Molding magazine.

This corona treatting company is very good http://www.martignoni-srl.com/coronaTreatment.html. I would recommend you talk with them.

I am not a chemist but this is what I have learned about paint adhesion.

As mentioned in a previous post. Paint will not stick to surfaces such as polyproylene due to the lack of surface energy and the lack of free radicals. I found out that poly vinyl alchohol (PVA) is a major deterent to adhesion. PVA is used in Teflon and hence there is no food adhesion to the pot. PVA is also used in printing inks.

In order to increase adhension, you need to increase the surface engery of the base material. Heat treating, flame treating, or AdPro, (I used plasma to increase the surface tension and hence get my paint to stick, but I had access to a university lab!)

In short, if you want to get paint to stick you must remove the PVC and increase the surface energy. Not always an easy thing to do.

I hope I did not complicate your issue.

I don't know how exactly adhesion is achieved in this case - but there IS ink that sticks well to polypropelene without pre-treatment of the surface:

http://www.inkcups.com/inks-thinners/complete-ink-list/dp/Default.aspx

Hope this helps