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topic 6159

Improving adhesion of paint to polypropylene

Current question and answers:

February 9, 2021

Q. I come here often to learn -- but there is one thing that puzzles me here which I am hoping someone could please clarify for me.

I know that PP is very difficult to bond to other than with special hot melt and cyanoacrylate with primer BUT it seems there are a few paints and primers which DO adhere quite well.

For low structural requirements (keeping rain out, making something dust proof or tamper resistant), then why can paint not be also be used a kind of "primer for glue"?

I know the idea of bonding to paint is generally considered terrible BUT if the joint needs to just be "reasonable" and not "structural", is there a reason why this idea would not work?

I have some boxes which I am using as economical battery case for some solar storage and I want to seal the tops to keep rain out - hence looking at options to allow me to "glue" a piece of PP on the top to keep everything inside dry.

As I say, I come here to be educated, so please forgive what is perhaps a stupid question.

Mark Tibbert
- Wellingborough, Northamptonshire, UK
^- Reply to this post -^

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February 15, 2021

A. Probably uncured tacky paint can be used. Silicone sealant can be used too.

Hope it helps and good luck!

Goran Budija
- Zagreb Croatia


February 15, 2021

thumbs up sign Thanks Goran Budija, I have not tried "sticky paint" but I have had modest amounts of luck with VERY hot hotmelt glue, mixed with PP "fluff" (toy stuffing).

I have tried silicone sealant on untreated PP as well as pre-treating with acetone, xylene, ethyl acetate and others.

Have not found any way to make silicone seal to PP unfortunately. Was thinking of trying benzine as that is supposed to be unsuitable for use with PP - so presumably does SOMETHING to the outer layer.

Thanks for the thoughts, much appreciated. I am going to try bonding test pieces with an assortment of glues on top of an assortment of inks and paints. In the (perhaps unlikely) event I find anything interesting, I will share my findings.

Mark Tibbert [returning]
- Wellingborough, Northamptonshire, UK
^- Reply to this post -^


February 16, 2021

A. Gold leaf size glue (oil based not modern water based) can be used probably but it is too expensive. That is sort of tacky oil varnish. I think that you can prepare your own tacky varnish-glue from hot sunflower oil and some beeswax and rosin...

Hope it helps and good luck!

Goran Budija
- Zagreb Croatia


March 9, 2021

A. You could try applying a film of primer solution - chlorinated or functionalised polyprop emulsions. In conjunction with abrasion, this can produce strong durable bonds using most common adhesives.

Tim Norris
- Manchester, UK


March 10, 2021

thumbs up sign Thank you for that Tim, this sounds very interesting indeed.

Q. Do you happen to know of any products a D-I-Y person is likely to be able to buy in the UK of the type you mention (chlorinated or functionalised polyprop emulsions)?

I am fairly resourceful, but if you happen to know a product name / brand name / "trade" name I could search for please, that would help me get the right one.

I did try Google, but although I found a wealth of scholarly articles on the matter, I didn't spot any "buy 500 ml of gloop here" type results.

Thank you again for taking the time to share your thoughts, it sounds encouraging.

Mark Tibbert
- Wellingborough Northants, UK

----
Ed. note: For 33 years now brand names / "trade" names have been the bane of this site (why?). But I suppose if a reader wants to simply offer a name without a testimonial we can try it and see whether it explodes on us yet again :-)




Previous closely related Q&A's starting in:

2000

Q. I am a project manager for a custom injection molding company in Ohio. We are currently developing a project for a major window & door manufacturer. Our goal is to mold window & door frames from a natural colored 20% talc filled polypropylene. These frames will be finished by consumers--probably using common latex paint. Our problem is that polypropylene has poor adhesion to coatings. We want to develop methods for surface treating (rather than base coating) that will allow adhesion of latex house paint for up to 2 years (possible retail store shelf life). Any insights would be greatly appreciated.

Rick Felumlee
- Frazeysburg, Ohio
^- Reply to this post -^


2000

A. Rick,

Had you asked me that question a month ago, I'd have said 'tough bananas' as I know of/knew of no adhesive that would bond well to either PP or Pe.

But the other day someone said that there's now a bonding agent for adhering fibreglass to Polypropylene ... in the plastics (chemical) fabricating field in the past, one has had to use heat fused glass fibres in order to bond FRP to the PP.

Apparently this is an adhesive ... so may I suggest that you contact your local fibreglass resin SUPPLIERS to see if there's any truth at all about this adhesive. Personally, I'd have my doubts.

By the way, natural PP, talc filled or not, will eventually U.V. degrade unless it has U.V. fillers (Carbon black, etc.) but you'd know that, I'm sure.

I wish you luck,

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



2000

A. Hi Rick

Although you say you don't want to coat I have done some work on water borne primers for automotive that may fit your need. These coatings were for aftermarket polypro parts. The project never completed due to the issues brought on by consumers vs insurance companies; however, a factory applied type primer finish may be viable.

Good Luck

Gordon Vidt
- Newark, Ohio


2000

A. Rick,

Further to my previous reply, may I make a comment?

Why in the hell are you using PP?

Why don't you use PVC? Most window mfgrs use PVC. It is much More resistant. It can be painted more easily. It doesn't have such a high coeffic. of thermal expansion. Parts' quality would, I think, be much more easily controlled.

Lastly, this may cost less to do apart from having less painting hassles.

The only advantages that PP has over PVC is a somewhat better resistance to temperature and to some solvents like acetone. C'est tout!

I should have mentioned this before. Sorry.

Cheers !

freeman newton portrait
Freeman Newton [dec.]
White Rock, British Columbia, Canada

(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



2003

! Hot melt PP based adhesives, while not considered to be "structural", will bond to untreated PP. YH America or Aica could help you. If anybody has found anything else to bond to it without surface treatment, I'd love to know about it.

PP is a straight chain simple hydrocarbon, and is eaten up by UV. Vinyl is much better, in part due to its structure. Why is PP being pushed in applications where it really doesn't fit (i.e., outdoor, painting, bonding)?

Because it's CHEAP. This is what happens when the accountants take control of material selection. Let me know the name of the windows, so I can avoid them.

Why not try to bond to Teflon, while we're at it? Oh wait, it ain't CHEAP.

Brian D. Witt
- Flora, Illinois


2004

thumbs up signThanks guys for making this understandable to the layman. My tale. I purchased an 04 Bayliner 285 and had the letters stenciled on the transom rear facing door of this boat as the Coast Guard recommends (3 inch letters etc). The problem? The lettering didn't stick as was promised by the technician / installer. We were all perplexed, confused and generally walking around with wrinkled brows. So I took the piece (30" X 18" porous surface) to a local plastics Guru. He came out of his lab smiling saying this was polypropylene.

Q. Now, the question is simple...do I resurface so the stencil will adhere better or do I determine a paint that will securely adhere to the original porous surface.

Appreciate your response!

Mike Musso
- Oceanside, California
^- Reply to this post -^


2004

A. I found this thread while searching for a similar need for allowing acrylic (waterborne artist) paints to adhere to PP.

"Although I am searching for a clear product to act as a primer/tie coat, I would suggest the easiest solution for this person is to buy some of the Krylon Fusion [affil. link to info/product on Amazon] spray paint, and make a masking tape stencil for the lettering onto the boat hull. Although my company is in no way affiliated with Krylon, they make some pretty strong claims that Fusion will adhere to normally hard to coat plastics."

Mike Townsend
- New Berlin, New York


2005

A. Adhesion promoters are commonly used in the automotive aftermarket for painting polypropylene and thermoplastic polyolefins, among other plastics. A light or mist coat of Bulldog Tie Coat [affil. link to info/product on Amazon] applied before the top coat provides excellent adhesion. It can even be mixed in some solvent based paint systems.

John Power
- Memphis, Tennessee


2006

Q. I've tried everything on this stuff: Krylon Fusion, Bulldog, PO Primer, Washing Sanding with ajax & a scotch brite pad & then trying the primer techniques again in still comes off and if you get the surface warm that your painting it comes off like dead skin and any minor impact it breaks apart. My main staple for business is painting children's batting helmets but some of these helmet companies are just cutting too many corners. Hell when you put a flames test on this stuff you might as well put a wick on this so called plastic and have yourself a candle. IF ANYBODY FINDS A SURE FIRE WAY TO MAKE PAINT AND CLEAR COAT BOND TO THIS STUFF LET ME KNOW.

Joseph Lott
- Jasper, Alabama
^- Reply to this post -^


2006

A. I believe that a product called BONDiT A-43 will satisfy your needs regarding a primer for painting polypropylene.

Kath Thomas
- Santa Rosa, California


affil. link
Bumper & Cladding Coat Adhesion Primer

2007

A. OK, on the issue of painting polypropylene. YES IT CAN BE DONE! The bumpers on virtually EVERY car out there are made of Polypropylene or a blend thereof.

Painting it is as easy as painting everything else if you know what to use. First, clean the RAW plastic with a product called Super Clean Plastic Cleaner (part number 1000-A) =>

This will remove any waxes, residues, mold release agents, etc. Then spray a product called Bumper and Cladding Coat Adhesion Primer =>

on the plastic...

There is no need to scuff or sand the plastic.

Use a NON-Catalyzed paint to color it however you like. If you want to use a paint with isocyanates, you need to have a dry non-isocyanate containing paint in between...otherwise the adhesion will go out the window in a big way.

Scott Bixler
- Rainsville, Alabama


June 12, 2008

A. First you heat the piece with a benzene touch hot but not too hot. Before it cools wipe down with denatured alcohol wipes. Just pouring denatured alcohol on a rag will not work. Then prime with catalyzed urethane primer. Test it for yourself.

Joe Sides
- Murchison, Texas


April 13, 2010

A. Lots of things don't work on PP. Complicating the issue is that it can sometimes have mold release agents on it as well. Here's the process that will get paint to stick and stay (though it can be worn off it will not flake or fall off without wear).

1) Clean the thing being painted
2) Clean the thing being painted with Transtar 1004 Prep wash. This is phosphoric acid and you might be able to just use that but I don't know for sure and I don't know the concentration. Clean everywhere and everything you're going to paint. No cleaning = no nice looking paint sticking.
3) Prime with either 3M 05907 Polyolefin adhesion promoter or Transtar 1023 TPO Adhesion promoter. I've tested these two and both work. Neither seems better than the other but they are both $30 for a single spray can (ouch, but no one said it would be cheap). Again prime everywhere and everything you want to paint. This stuff apparently slightly changes the chemical makeup of the surface of the PP to make the paint stick. I had to go through research papers, a company in Japan and a very surprised chemical engineer who has probably never before gotten a call directly from a customer.
4) Paint. I have used Rustoleum Appliance Epoxy. Krylon Fusion might work, but I have found it lacking in other plastic situations. Their standard interior/exterior works better on ABS than Fusion.
5) Let the thing dry for at least three days.

David Jannke
- Dallas, Texas


April 16, 2010

A. Have you ever heard anything about atmospheric plasma systems? It could be useful for painting PP materials.
There is only initial investment costs, not continuous costs.

Hope this info can help you.
Take care.

Cuneyt Gencal
- Kocaeli, TURKEY


January 11, 2011

If you may concerning the above problem, you would get more useful answer from under described information.

Notice the term : AMAPPA
AMAPPA means PP-g-MAH-Polyetheramine (MAH:Maleic Anhydrate)

There are two type of AMAPPA
1. Resin Type : Mixable with PP Resin
2. Emulsion Type : Like Primer(waterborne and solventborne)

Dalwoo Kim
- Seoul City, South Korea


May 23, 2012

Q. Hi,

I have read the many helpful responses, and am now more confused! I have a 'dart 16' rotomold sailing catamaran, and the surface is really waxy, so to apply a name for the boat, stickers last about 3 sails before they wash off.so paint.... Which of the above would be the best one off solution for applying a name to my boat WITHOUT destroying any of the hulls strength?

Chris

Chris Jones
- Limassol, Cyprus
^- Reply to this post -^


February 10, 2015

A. I am a Coating Chemist. We are often approached to develop coatings to stick to polyethylene-polypropylene. These are known as olefins. Unlike other plastics that have surface molecules to adhere to, PE and PP are totally inert and nonreactive. They have low surface energy. Flame treating or corona discharge can produce oxidation and create hydroxyl carboxyl, and carbonyl- polar groups that the paint can adhere to. Another method is a thin low solids primer called CPO - Chlorinated Polyolefin. Kind of like the polyethylene itself with chlorine groups on it. This is soluble in only toluene or xylene and is applied very thin and this will make the PE PP paint-able, PP and PE are used all the time but people do not realize how hard it is to adhere to.

Mike Luckett
- Elkhart, Indiana


February 14, 2015

A. Polyethylene and polypropylene are called polyolefins. The surface of this material is nothing other then hydrogen atoms. Basically there is nothing for the paint to associate with. By the way I am a paint chemist. The surface tension is low. Low surface tension makes the Teflon fry pan non stick. If the paint can not wet the material well it will not adhere. There are ways to paint this however. Everyone is tempted to take short cuts but they will fail. A Poly Olefin Primer may be applied. This is made of a Chlorinated Polyolefin produced by Eastman Kodak. It is only soluble in Toluene or Xylene. It is best applied at low solids 2-3% or 97% solvent. The applied film is very thin and the subsequent coating is put over this, The CPO sticks to the PP and the paint sticks to the CPO primer. Other ways are to flame treat or plasma treat. What this produces chemically , are carbonyl, hydroxyl, or carboxyl molecules on the surface of the treated material. These groups give the paint something it can sink its teeth into. These are methods that do work. What happen every time is the Mfg. produces a part and then decides to paint it. The molding material is the critical piece to the painting ? Simply said PE and PP are very difficult to adhere to. All due to the inert surface.

Michael Luckett [returning]
- Northville, Michigan



March 24, 2015

Q. To Michael Luckett and others,

I'm a waterborne acrylic artist painting on Yupo paper(100%PP). To get better paint adhesion to the untreated PP surface, I use a chlorinated polyolefin called 10-pp wipe primer. It is designed to make screenpint ink adhere better to PP.

6159

My question is what is the shelf life of such a primer when covered with a layer of acrylic paint? And: it's a solvent-borne primer and I put a waterborne acrylic paint on top of it. Will the acrylic paint remain attached to the primer over time?

Maarten Frenken
Artist - Den Bosch, The Netherlands
^- Reply to this post -^


November 27, 2015

A. As well as the paint you use, the application technique (especially when using stencils) can cause the paint to peel.
The most common cause is down to applying the first coat of paint too thick or maybe not timing the re-coats correctly.
As different paints require different techniques, it pays to read and understand the instructions

Glenn Roads
- Hervey Bay QLD Australia


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Liberon Steel Wool
rocklerSteelWool

November 14, 2016

A. To get paint to better adhere to poly.

1 Clean plastic with cleaner, e.g., "ZEP" [affil. link to info/product on Amazon]
2 Scour plastic with 000 steel wool =>
3 Clean plastic with cleaner e.g., Zep.
4 Gently heat plastic with propane torch until surface looks oily.
5. Clean with alcohol until surface is free of oil.
6. Paint with plastic primer.

Lane Romel
- Brantfor, Ontario, Canada


January 4, 2019

A. Hi, I'm Amanda S. From Kentucky and I happened across this conversation in pursuit of some answers of my own. I've been dabbling in adhesives in many of my art projects. I'm not sure it this will work for a base but it's worth a shot, and it's an inexpensive experiment that may also be beneficial to your cheap skate superiors: Make a stencil for the lettering with tape or whatever you use, then fill the stencil with baking soda and pour liquid super glue on top of the baking soda (try to stay inside the stencil). This stuff dries instantly and can be sanded down for a smoother surface. Paint the letters after a quick sanding, and good luck! Hope it works out for you.

Amanda Singhiser
- Louisville Kentucky USA

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