Working with resin/ Primer

[my80malibu]

Ok my familiarity with resin is limited,

I have two projects both resin. I have soaked the bodies in Wesleys Bleche white for 24 hours, washed them with dawn dish soap. Used a self etching primer from Rust Oleum. now the primer is peeling from my bumpers. I tape tested the other parts they seem ok the primer is soft though. What could be the problem? Should I strip the primer off?

[Roncla]

If the primer is soft and peeling I'd definitely be stripping.

Think of your primer as the foundations. if it isn't right nothing good can come from continuing.

I would be looking in to the compatibility of your etching primer with resin.

[bill w]

I think etching primer is for metal only!

Bill

[martinfan5]

Gab, Get a can of Mr Hobby Resin Primer, Hobby Depot sells it

[Tom Geiger]

I use Duplicolor primer gray as a base for just about everything. It's automotive primer so it covers anything, and can be coated with anything!

[Chief Joseph]

Self-etching primer really won't do anything special for resin; regular Duplicolor primers or hobby lacquer primers are all you need. Did you rinse the parts in plain water really well after using the dish washing liquid? A lot of guys will scrub resin parts with Comet cleanser and a toothbrush-- that works really well to prep parts for primer.

[my80malibu]

Typically Duplicolor Primer is what I use exclusively. This time I was experimenting trying to get a better bite into the resin. Joseph, I did rinse well after the dish soap. I did think about scrubbing the parts with some Tide. I have heard about using Comet though.

Not to get off of the subject. There are a few different resins that I have seen recently, it is becoming difficult to know exactly what to do with them, in terms of prep, and what they are made of. I recieved some resin door panels, and seats from Ed Fluck. Beautiful work, they looked like you could just paint them on the spot.I also recieved a Body from Bandit Resins Very good casting. I dont much care for the resin, although its white, and odorless it appears softer, and more flexible. That is almost like Styrene plastic VS Bakelite.

Edited March 14, 2014 by my80malibu

[astroracer]

Again, there is no need to "soak" the resin in anything before prepping for paint. This was discussed here a couple of years ago. Soaking in Bleche White does NOTHING to help clean or prep the part for finishing. I have NEVER done this and have never had an issue with paint adhesion...

The BEST thing you can do is get a box of TSP (tri-sodium-phosphate) at your local hardware and wash/scrub the body, inside and out, with hot water and a bit of the TSP. The TSP will remove all of the silicone residue from the molding process and, if you use a ScotchBrite pad to wash/scrub the body, it will be just about ready for primer when it is fully dry. Use a good automotive grey primer like Plasti-Kote or Duplicolor and you should be fine. Keeping the parts clean and oil free after washing and sanding is key. Do not handle the parts with your bare hands before painting.

I use the same prep for molded kit parts. There is no difference.

Mark

Edited March 14, 2014 by astroracer

[Art Anderson]

Again, there is no need to "soak" the resin in anything before prepping for paint. This was discussed here a couple of years ago. Soaking in Bleche White does NOTHING to help clean or prep the part for finishing. I have NEVER done this and have never had an issue with paint adhesion...

The BEST thing you can do is get a box of TSP (tri-sodium-phosphate) at your local hardware and wash/scrub the body, inside and out, with hot water and a bit of the TSP. The TSP will remove all of the silicone residue from the molding process and, if you use a ScotchBrite pad to wash/scrub the body, it will be just about ready for primer when it is fully dry. Use a good automotive grey primer like Plasti-Kote or Duplicolor and you should be fine. Keeping the parts clean and oil free after washing and sanding is key. Do not handle the parts with your bare hands before painting.

I use the same prep for molded kit parts. There is no difference.

Mark

I second what Mark is saying here: Bleche White contains TSP as its active ingredient, Spic n Span household cleaner is also TSP,, and is very easily found in the household cleaning supply area of your favorite supermarket.

As for cleaning resin parts beforehand, the best resin parts such as Modelhaus may have a mold barrier coating on them, most generally Price-Driscoll Ultra Parfilm. Top quality resin casters use this to extend the surface life of their molds which results in much smoother castings. The silicone RTV rubbers that nearly all casters use is slightly porous, meaning that it tends to absorb some of the liquids that make up both the polyurethane resin and its catalyst. This leads to a deterioration of the mold surfaces, making resulting castings have a rougher surface, and eventually causing the resin to bond to areas of the mold as it hardens, tearing the mold and rendering it useless. Ultra Parfilm is paraffin based, whilch while P-D claims it to be paintable, does interfere with adhesion--so cleaning the parts beforehand is highly recommended.

Another alternative cleaner is ordinary naptha, a/k/a lighter fluid, which will remove any Parafilm residue very quickly and holds it in suspension so that it does not "redeposit" on the resin surfaces. Polyurethane resin is also highly resistant to naptha as well. Naptha is still readily available in hardware and paint stores, at in the paint department at Walmart.

For the ultimate in paint adhesion on polyurethane resin, there are several "adhesion-promoting" primers available in the autobody trade--used when your body shop paints a new soft bumper cover (those generally are made from a soft, flexible polyurethane). I used to use a clear adhesion primer on all parts that were to be plated, as the pre-coating lacquers used in vacuum metalizing don't always stick that tight to resin castings. This was, and still is made by SEM, and I can still find it at my local store catering to autobody shops and restorers. It is very smooth, semi-gloss, and doesn't hide surface details, and can be painted over with ordinary primers as well.

Art

[bill w]

Plas-stick #2322S is made by Dupont, it's a clear adhesion promoter for plastics.

[astroracer]

You guys are making this much more difficult then it really is. Adhesion promoters are not necessary... If the parts are clean, oil free and well sanded the base primer will have plenty of adhesion. The plastic has to be sanded to provide a tooth for the primer to adhere to. I use Grey ScotchBrite pads pretty much exclusively for this initial sanding. They work much better then sand paper at getting into the little nooks and crannies presented by the small parts. Like I said in my first post, if you use the ScotchBrite to wash and scrub the body it will be nearly ready for primer after it's dry. This applies to kit as well as resin bodies.

Mark

[my80malibu]

All of the advice given here is very much appreciated. I will try the TSP/ Scotchbrite method as soon as I can. The Adhesion promoter is a bit on the Pricey side for me right currently. I want to hold off on that Extreme for now.

Gabriel

[Danno]

Gabe, I've never had any problem when using the Bleche Wite soak - Dawn wash - Duplicolor primer process. But, part of my success may include using only best quality resin castings to start with. Modelhaus, Promolite, Greg Wann, Bandit, Missing Link, All American products are clean to begin with. I've had no problems with Flintstone and most R&R, but I take more care to clean the typical R&R.

I've had problems, even with Bleche Wite when trying to use certain other resin castings. The more aggressive procedures described above would probably be worthwhile with most other casters.

[Joeys Models]

I use automotive quality greass and wax remover. 3M is a good brand. But Turtle Wax sells a bug and tar remover at the parts store. Same thing. Removes all wax and sillicon. Just wipe it downd with a well soaked rag. Do this before any sanding is done to you parts. Use it again before you paint. Removes oily finger prints.