Static Electricity???

[coopwyo]

Has anyone ever had a problem with pain "crazing" on a large plastic nose cone for like the Big Red Max? I painted mine and it ended up having a million little cracks in the paint show up while it was drying. It has never happened to me on a small nose cone, but it happened twice on the big one. Could it have been static electricity left over from when I sanded it and then wiped it down? Any help would be appreciated.

 

[neil_w]

What paint did you use, and what was the exact timing of your different coats?

 

[coopwyo]

What paint did you use, and what was the exact timing of your different coats?

I used original, gloss black, Rustoleum. It happened on the first coat. There were several days between coats because I had to let it dry and then sand it down again to get rid of the crazing.

 

[neil_w]

No primer?

 

[coopwyo]

Yes, grey Rustoleum

 

[neil_w]

Again: what was the timing of your coats? This includes primer, everything.

 

[coopwyo]

Again: what was the timing of your coats? This includes primer, everything.

24 hours between primer and the first coat that cracked.

 

[Rob Campbell]

I've had it happen. The only fix is to wet sand it out and reapply paint.

 

[cls]

How did you prepare the nose cone, before applying primer?

I like using orange cleaner, to get the PVA mold release off the surface. That dries quickly and doesn't leave any VOC residue. Cleaning with alcohol or acetone (yuck) or Simple Green (double yuck) might have left something on the surface?

 

[coopwyo]

I cleaned it with acetone both while it was still raw plastic and after priming

 

[RocketTree]

24 hours between primer and the first coat that cracked.

I usually let the Rustoleum 2X primer flash off for a week before sanding and painting. Duplicolor automotive primer only needs a couple days in my experience. Do a sniff test - if you can smell the primer, it might not be ready for painting. Im sure there are other instances where you could sand and paint sooner, but after painting over 80 rockets with Rustoleum 2X, I found those issues were usually caused by waiting too long between coats, or not waiting long enough after the recoat window has expired. Some colors are seemingly more problematic than others.

 

[neil_w]

1) Sometimes there is no explanation for this sort of thing. At least, nothing that you can pin it on with any certainty. Sometimes is just happens even when you think you've done everything exactly the same as always.
2) 1 day cure for primer might have been short. I normally leave at least 2 days for it. Realistically this is the most likely explanation.
3) @hcmbanjo has written on his blog about how he has learned to give plastic nose cones extra cure time
4) I tend to doubt static electricity had anything to do with it; I've certainly never heard of this as an explanation before.
5) Whatever the reason, it certainly sucks

 

[cls]

I cleaned it with acetone both while it was still raw plastic and after priming

ah! probably the acetone after primer. not necessary at all.

sand it down and try again.

we all forgot to ask: what was air temperature and humidity the days you painted? I feel humid air doesn't let the VOCs (acetone, spray solvents) evaporate as quickly as dry air.

 

[coopwyo]

It was about 80 degrees with very little humidity. I cleaned it with acetone after wet sanding the primer to get all the dust and sanding residue off before painting. Should I have just used water? I felt like that wouldn't work as well on the fingerprints, etc.

 

[ljwilley]

I had a lot of trouble painting my mega der red max nose black. It wrinkled up. I ended up painting it grey instead.

 

[neil_w]

It was about 80 degrees with very little humidity. I cleaned it with acetone after wet sanding the primer to get all the dust and sanding residue off before painting. Should I have just used water? I felt like that wouldn't work as well on the fingerprints, etc.

I normally use alcohol.

 

[cls]

I wear nitrile gloves to prevent finger oil issues.

 

[kjhambrick]

I cleaned it with acetone both while it was still raw plastic and after priming

@coopwyo --

I am famous for my ugly rockets and one particularly ugly rocket was because of an acetone rubdown on my primer coat.

Acetone is not your friend around green uncured paint -- it is much too harsh.

As @cls said, alcohol ( isopropyl or ethanol ) or even water might be better.

-- kjh

 

[OzHybrid]

What about flame treating the nosecone surface. Doesn't that promote better paint adhesion. Something about the chemical change at the plastic.

 

[neil_w]

What about flame treating the nosecone surface. Doesn't that promote better paint adhesion. Something about the chemical change at the plastic.

Adhesion doesn't really seem to have been the issue here, is it?

If that were my concern I'd probably just go with some sort of plastic adhesion promoter (not a bad idea in general, but not always necessary depending on the particular variety of plastic).

 

[OzHybrid]

Adhesion doesn't really seem to have been the issue here, is it?

If that were my concern I'd probably just go with some sort of plastic adhesion promoter (not a bad idea in general, but not always necessary depending on the particular variety of plastic).

Usually if you've got cracking, it's the paint not bonding to the base then shrinking as it dries. Here's a wiki link
https://en.wikipedia.org/wiki/Flame_treatment

 

[SkyFire]

 

[rcktnut]

For all my plastic nose cones, I wash good with soap and water, then sanded with 220 paper and then wipe with alcohol. I've always used water after sanding any paint coating. Just make sure the surface is completely dry before recoating. I know that especially acetone and also 91% alcohol "bites" into paint even very well cured. Acetone will "eat" certain plastic also.

 

[OzHybrid]

For all my plastic nose cones, I wash good with soap and water, then sanded with 220 paper and then wipe with alcohol. I've always used water after sanding any paint coating. Just make sure the surface is completely dry before recoating. I know that especially acetone and also 91% alcohol "bites" into paint even very well cured. Acetone will "eat" certain plastic also.

View attachment 601440

What time can I pop round with my nosecones? Very nice.

 

[OzHybrid]

View attachment 601397

Plastic adhesion promotor is good, but the plastics in cars will still allow solvents to get a bite as the ABS used for a lot of bumpers will dissolve somewhat in them. The plastics used for nosecones, polypropylene and polyethylene are much more resistant to solvents. This is where the flaming process comes in as it changes the chemical structure on the surface interface.
Here's a copy of the procedure for some large domes we bought for a project from the manufacturer. The process is appropriate for our types of nosecones although they will be thinner and you'll need to be careful. Polyethylene and polypropylene are polyolefins.

 

[OverTheTop]

I have tried to use flame polishing to promote adhesion when building some fins with an ABS core CF skins. It sort of worked, but was very process dependant. Went back to more traditional FG core for the flight parts.

 

[rharshberger]

What about flame treating the nosecone surface. Doesn't that promote better paint adhesion. Something about the chemical change at the plastic.

its called a corona treatment or flame corona treatment iirc, not necessary on polystyrene nosecones like Estes but can be beneficial on polypropolene nosecones like most HPR NCs are.

 

[prfesser]

Technical-grade acetone (Lowes, paint stores) *may* contain traces of some odds and ends that inhibit adhesion. I prefer not to use it. Thorough scrubbing with water and a good detergent (Dawn), followed thorough rinsing, drying, and the flame treatment described above, is effective on polypropylene nose cones.

The crazing described by @coopwyo is most likely some type of paint incompatibility. As others have mentioned, allowing primer or paint to dry thoroughly is a very good idea. Having seen similar crazing on some plastic parts, I either recoat within the recommended time, or wait at least a week. It's too much work sanding off my mistakes; I'd rather wait longer than take the chance.

 

[jqavins]

Does this flame treatment that promotes paint adhesion also do any good for epoxy, CA, or other adhesive adhesion?

 

[OzHybrid]

Does this flame treatment that promotes paint adhesion also do any good for epoxy, CA, or other adhesive adhesion?

It's specific to polyolefins. Polypropylene and polyethylene. Commonly used for blow moulding. It improves wetting which allows the paint to stick better. I'm not a paint expert. Just had to do it recently on a job and those were the instructions for cleaning and prepping the surface.
Others might have more experience in the full range of plastics this would be useable on.