paint on plastic nose cones

I remember having a heck of a time painting plastic nose cones, specifically on Aerotech models but possibly Estes ones too, years ago. They came out looking fine at first, but were super susceptible to scratching and chipping. Was I simply using the wrong type of paint, the wrong technique, or in this a common problem for most users of those types of plastic?

It is often tough. I wash down with mild detergent, wipe with acetone (standard polypropolene is not damaged by acetone), sand well with 100 grit, wipe with acetone again. Then when you are ready to prime, first spray with Duplicolor Adhesion Promotor, wait 3 to 5 minutes and then proceed with filler-primer. Then do the typical prime/sand (180 to 220 grit) cycle until you are happy it is smooth enough, then apply a white base primer. I might do a couple rounds of sanding (320 or 400 grit) of that and then apply one to three color coats fairly quickly with very light progressing to heavy coverage. I don't sand between color coats if nothing gets into the mix (bugs, dust, etc.). If they do, I will typically wait until dry 24+ hours, then do a light sanding concentrating on the blemish and then do another light, then full color coat. Following the above procedure, for the most part, I haven't had nosecone chipping on plastic or fiberglass for about five years (before that it was hit/miss).

dixontj93060 said:

It is often tough. I wash down with mild detergent, wipe with acetone (standard polypropolene is not damaged by acetone), sand well with 100 grit, wipe with acetone again. Then when you are ready to prime, first spray with Duplicolor Adhesion Promotor, wait 3 to 5 minutes and then proceed with filler-primer. Then do the typical prime/sand (180 to 220 grit) cycle until you are happy it is smooth enough, then apply a white base primer. I might do a couple rounds of sanding (320 or 400 grit) of that and then apply one to three color coats fairly quickly with very light progressing to heavy coverage. I don't sand between color coats if nothing gets into the mix (bugs, dust, etc.). If they do, I will typically wait until dry 24+ hours, then do a light sanding concentrating on the blemish and then do another light, then full color coat. Following the above procedure, for the most part, I haven't had nosecone chipping on plastic or fiberglass for about five years (before that it was hit/miss).

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This is the same method I use, same products and it works well. For me I put it to test this past summer. I built an Aerotech Mustang and on it's maiden launch she weather-cocked right over and took off like a missile 100 feet off the ground slowly arcing over into a corn field. I found it an hour later all crumpled up like an antenna. Despite the nosecone being burried 6 or so inches when I pulled it out all of the paint was there not a single bit was peeled off. I still have the nosecone.

I just painted two identical plastic nose cones prepared in the same manner.

I had them stuck on either end of a length of BT 50 and shot them from the same spray can at the same time.

One came out great the other looks like crap.

?????????? Not a clue.

Unfortunately, today's plastic nose cones require a great deal of attention. You can hardly glue anything on them or in them without proper surface attention. This is partly what made me invest in a lathe. It's a helluva lot easier to finish a balsa or basswood cone, than all the crap you got to do with today's plastic. I'm sure it's easy to whip out the card, and go with the easy availability, but consider the craftsmanship of making it yourself. Is that just too much trouble?

I have had excellent sucess with all my poly nosecones by doing the following.
Clean in warm soapy water.
Rinse and dry.
Wash with acetone.
Sand with 120 grit paper
Spray a light tack coat of rustoleum plastic primer and let sit for 5 minutes followed by a second heavier coat.
Let dry for 24 hours
Sand off the fuzzies with 220 grit.
Respray a light final coat of rustleum primer and let cure for 5 to 7 days. THE PRIMER GETS NICE AND HARD.
Wet sand with 320 grit.
Spray your usual primer filler. I like SEM professional spray can primer filler but rustoleum is ok too
Scuff the dry primer with 320 or 400 git or even better, a grey scotchbrite pad.
Spray final coats.
A lot of work, but a perfect finish that you can take a hammer to.

DavieRockets said:

I have had excellent sucess with all my poly nosecones by doing the following.
Clean in warm soapy water.
Rinse and dry.
Wash with acetone.
Sand with 120 grit paper
Spray a light tack coat of rustoleum plastic primer and let sit for 5 minutes followed by a second heavier coat.
Let dry for 24 hours
Sand off the fuzzies with 220 grit.
Respray a light final coat of rustleum primer and let cure for 5 to 7 days. THE PRIMER GETS NICE AND HARD.
Wet sand with 320 grit.
Spray your usual primer filler. I like SEM professional spray can primer filler but rustoleum is ok too
Scuff the dry primer with 320 or 400 git or even better, a grey scotchbrite pad.
Spray final coats.
A lot of work, but a perfect finish that you can take a hammer to.

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Like I said..............

Thanks all! Any reason to, or not to, do this with my plastic fins? I do not recall having as many problems so perhaps they are a slightly different material.

Gary Byrum said:

Like I said..............

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The major difference is the plastic primer vs adhesion promoter. The plastic primer stays tacky for days as it critically bonds to the pores and hairs of the sanded surface. I find that slow drying products bond better and that's why I chose it. The plastic primer is also very flexible which I think is key to taking a lot of abuse without chipping. I will try some adhesion promoter next time to see if I can eliminate the suggssted week of waiting before final sanding and top coating without giving up the robustness of plastic primer.

watermelonman said:

Thanks all! Any reason to, or not to, do this with my plastic fins? I do not recall having as many problems so perhaps they are a slightly different material.

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Typically plastic fins are styrene or polycarbonate plastic, not polyethelene so they take paint easily without going to the necessity explained previously. But be careful to use paint designed for plastics as the strong solvents can partially dissolve those plastics and leave a rough or mottled finish.

Polyethelene on the other hand is not dissolved or etched by any paint I know of hense the adhesion issues if not sanding and using a plastic primer first.

What DavieRockets said about the plastic primer.

I have successfully used it on those Madcow nose cones that simply reject paint.

Wash, scuff the surface up with 60 grit to raise "hair" on the surface, spray with automotive plastic primer. A heavy coat is not required. Now for the hard part: WAIT THE RECOMMENDED 7 DAYS before you even thinking about doing anything with the nose cone.

Once the "curing/bonding" period is done, spray with normal primer and let it cure fully, too. Lightly sand as needed and re-prime until the surface is as smooth as you need it to be (wash-rinse-repeat) for the color coat. If you clear coat like I do, it doesn't need to be glass-like as the Rusto Crystal Clear Enamel will shine up almost anything to a glossy smooth finish.

Be advised that if you prang your rocket, the paint on the nose cone and elsewhere WILL chip. It's part of the rocketry experience. I have repainted nose cones several times because I keep forgetting that rocketry is about poking holes in the sky rather than making pretty models.

DavieRockets said:

Typically plastic fins are styrene or polycarbonate plastic, not polyethelene so they take paint easily without going to the necessity explained previously. But be careful to use paint designed for plastics as the strong solvents can partially dissolve those plastics and leave a rough or mottled finish.

Polyethelene on the other hand is not dissolved or etched by any paint I know of hense the adhesion issues if not sanding and using a plastic primer first.

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Hah, yes I did some web searches before starting and decided it was not worth the risk of the acetone eating my fins. I still gave them a wash and some adhesion promoter, figured it could not hurt.

I used to clean first with lye based oven cleaner, rinse with water then acetone and paint immediately

M