Finishing Aerotech/polypropylene Nose Cones - best method?

The consensus I've seen seemed to be cleaning thoroughly, applying Krylon plastic primer, applying Krylon paint. If using other than Krylon paints, waiting at least a week, then adding whatever color is desired on top of the Krylon.

Problem is, I can't find Krylon Plastic Primer anywhere. Auto Parts, Big Box stores, hardware, etc. I guess I can try getting from Amazon for $12.XX/can. Seems a bit excessive.

Has anyone used the Krylon Fusion (for plastic) or any other primers/paints with any success?

Bill:
It's not so much the Paint that's causing the concern it's the Plastic. Poly-Propylene is notorious for NOT holding on the any type finish.
Yes I've painted Poly-Propylene models over the Krylon Plastic Primer (which I had to order by the way). with both Krylon Fusion Plastic paints and After a week dry time other brands of rattle-can paints.

The Only other "trick" I've used is to rough sand the entire surface of the object being painted with 80grit sandpaper to give the surface a good amount of "Tooth" for the Primer and paint to adhere to. This has for the most part kept the finished paint film in place on the Nosecone or model.
I guess the best example I have handy is the Narhams Flyin Pig. He's a Poly-propylene bank but if you look closely you'll see there are STILL a few spots where the plastic flexes on landing where the well sanded, primer, and paint as popped off
You might try just roughing up your nose cone for an application of Krylon Fusion Plastic paint but don't spend a bunch of time on it until you can fly it a time or two to see if just roughing it up will be enough to hold the paint film.
Keep in mind the only thing that really holds our paint to any surface is the lack of air between the surface and the dry paint film.
Hope this helps a little.

I've used the Valspar brand plastic primer, then Valspar regular primer on top of that with good results. Unfortunately the couple cans that I have are the old style. No one seems to like the new nozzles, though I have had good luck removing the outer locking ring, leaving the nozzle behind. (To do that I use a hack saw to cut the thin portion of the ring above the nozzle then rip it off with pliers). I do not know if the formula may have changed with the new can. YMMV

I wash with soap and water, light sanding with some 120grit, wipe with alcohol, then paint. Seems to have worked OK for me. My cones do have handling chips here and there from bouncing around in the minivan. They look good for the first couple flights though....

The goal of sanding or any other bond prep is to open up the molecular structure on the surface of the cone and make it amenable to paint. After doing several years of the sandpaper/primer cycle and still ending up with hardly any paint on the cone after a few flights, I was taught an easier and more thorough way to functionalize the surface of the plastic nose cone: take a torch and (lightly!) run it over all surfaces to be painted just prior to painting. You don't want to melt the surface-- just crack a few of the bonds near the surface so that the paint molecules have something to grab onto.

Haven't lost paint off a plastic nose cone since, even on dry lakebeds

daveyfire said:

The goal of sanding or any other bond prep is to open up the molecular structure on the surface of the cone and make it amenable to paint. After doing several years of the sandpaper/primer cycle and still ending up with hardly any paint on the cone after a few flights, I was taught an easier and more thorough way to functionalize the surface of the plastic nose cone: take a torch and (lightly!) run it over all surfaces to be painted just prior to painting. You don't want to melt the surface-- just crack a few of the bonds near the surface so that the paint molecules have something to grab onto.

Haven't lost paint off a plastic nose cone since, even on dry lakebeds

Click to expand...

You wouldn't happen to have a video of that process being used would you?

K'Tesh said:

You wouldn't happen to have a video of that process being used would you?

Click to expand...

I think I read about it in an old MDRA report, but I can't find it at the moment. It's not too hard-- just fire up the torch and run it quickly over all surfaces of the cone. If you melt the plastic, you weren't quick enough!

We use that technique to get paint to adhere to plastic blow molds (the plastic molded figures used in holiday lighting displays that have lit interiors).
Essentially you use a torch with a wide angle flame tip, just to heat the plastic up (this is after all the old point has been stripped).
You have to keep the flame moving, and avoid direct contact with the plastic. It's pretty easy technique to use, but will take a little practice, so use some scrap when starting out!
The trick is to then get the paint sprayed on while the plastic is still warm. It will certainly be a lot easier doing this on a nosecone, as opposed to a 3 ft or larger figure, which requires you doing it in sections, to avoid the plastic cooling too quickly.
For these figures we skip the primer, and go with the finish coat (as light has to project through it). These days we used Fusion which adheres well. We do not sand.
While the painted figures don't fly supersonic, they do hold up to well to rain, snow and ice, almost as well as the initial coat did (that used a heating process in manufacturing immediately before spraying.
Greg

If I were going to heat before painting, I have two options: propane torch and heat gun (older model than shown).




The torch doesn't have a wide setting - just a single point flame. Thoughts as to which would be better to use?

I was just going to ask the same thing regarding using a heat gun. (I have that same model; looks like one of the Harbor Freight cheapies.) Really depends on what temp profile is needed, I guess.

Tried using the heat gun. Don't think I got the NC hot enough, as the paint came off relatively easily. Not that it mattered in the end...

https://www.rocketryforum.com/showt...d-planned-L1-cert-attempt&p=716905#post716905

I have a bit of experience with the nose cones AeroTech uses. :wink:

The reason behind using a torch (not a heat gun) on the nose cones has to do with the molding process.
Blow molded nose cones come out of the mold with oils/mold release on them. This can prevent paint from 'sticking' to
the nose cone.
By treating the nose cone with a propane torch set to low this will burn off any oils that will cause problem with the primer/paint.

Just be careful when using the torch!