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Old 01-04-2007, 09:15 PM
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Epoxy over 2K and on polyurethane???

Hello,

I have brand new polyurethane body peices (front, rear bumper, and side ground effects) that are virgin. I will be painting ALL parts off the car. From reading posts on here and from listening from 3 different paint supply places i am very confussed now. My original plan was:

1. the pieces with soap and water
2. Clean with wax and greese remover
3. Sand with 400 grit and a red scotch pad
4. Clean with wax and greese remover again
5. spray bulldog adheasion promoter
6. Use Sem flexible primer surfacer or Nason 2K 421-19 primer w/bulldog added (was favoring the sem product)
7. then my base coat
9. clear coat with bulldog added.

Am i on the right track?? I have been reading a lot about the Epoxy primer and not sure if I would go with that? Sounds very impressive, but not sure if i can get spi epoxy primer locally. Any suggestions would be very much appreciated on which route i should take.

Also i have already done all the repair work and leveling to the rest of the body with fillers and the Nason 2K 421-19 primer that my supply suggested. Should i spend the extra time and money on the SPI epoxy primer and spray the whole car? what would be the benifits since i alread usedthe 2k urethane?

Thanks again for any help....

Troy

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Old 01-04-2007, 11:59 PM
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Quote:
1. the pieces with soap and water
Good.

Quote:
2. Clean with wax and greese remover
Be sure to use W&G remover made specifically for plastic.

Quote:
3. Sand with 400 grit and a red scotch pad
OK

Quote:
4. Clean with wax and greese remover again
OK, see above.
Quote:
5. spray bulldog adheasion promoter
OK

Quote:
6. Use Sem flexible primer surfacer or Nason 2K 421-19 primer w/bulldog added (was favoring the sem product)
I think the SEM might be a 1K product (no hardener). If so, don't use it. I'm not familiar with Nason 421-19. It may be flexible enough to use on plastic or it may not. Probably not, as it's cheap stuff. Don't use a different brand additive without being sure it's made to work with that specific product. Use the correct primer instead.

Quote:
7. then my base coat
OK

Quote:
9. clear coat with bulldog added.
Would not do it! Urethane clears stay pretty flexible on their own these days. Is there a bulldog product made specifically for this? I've not heard of it.

Quote:
Am i on the right track?? I have been reading a lot about the Epoxy primer and not sure if I would go with that? Sounds very impressive, but not sure if i can get spi epoxy primer locally. Any suggestions would be very much appreciated on which route i should take.
I like epoxy primer more the more I use it. You must be patient because it dries slowly. SPI has been performing well for me. If you want it you can get it shipped in with no problem.

Quote:
Also i have already done all the repair work and leveling to the rest of the body with fillers and the Nason 2K 421-19 primer that my supply suggested. Should i spend the extra time and money on the SPI epoxy primer and spray the whole car? what would be the benifits since i alread usedthe 2k urethane?
Main benefits are increased adhesion of the basecoat and increased chip resistance. A drawback is some epoxy overspray can sometimes get into the jambs and not be covered by the topcoat.
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Old 01-05-2007, 05:20 AM
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Great response Crashtech!!!
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Old 01-05-2007, 06:13 AM
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Thanks for the responce!!
Quote:
Originally Posted by crashtech
I think the SEM might be a 1K product (no hardener). If so, don't use it. I'm not familiar with Nason 421-19. It may be flexible enough to use on plastic or it may not. Probably not, as it's cheap stuff. Don't use a different brand additive without being sure it's made to work with that specific product. Use the correct primer instead..
The Sem primer is a primer that shoots straight out of the gallon or quart. What are the benefits of a 2K? What would you recommend because i am at the mercy of the supply guy that doesnt paint the stuff?

Quote:
Originally Posted by crashtech
Main benefits are increased adhesion of the basecoat and increased chip resistance. A drawback is some epoxy overspray can sometimes get into the jambs and not be covered by the topcoat.
I am painting everything off the car so i will be painting the jambs too. Is there anything different about spraying epoxy than 2k urethane. Like gun, tip, pressures, requires a more ventilated area, ect.... I tried some polyester primer and that was some really nasty stuff. Burned my eyes and smelled horrible.
Quote:
Originally Posted by crashtech
I like epoxy primer more the more I use it. You must be patient because it dries slowly. SPI has been performing well for me. If you want it you can get it shipped in with no problem.
If i sprayed the epoxy over the whole car to seal everything and the plastic pieces, how long would i have to wait before i can put the base coat down? and I assume i would have to sand with 400 - 600 prior to base coating??

Thanks again for your responce..


Troy
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Old 01-05-2007, 07:41 AM
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Quote:
Originally Posted by Mustangous
Thanks for the responce!!
You're welcome!

Quote:
...What are the benefits of a 2K? What would you recommend...?
Well, there are many, but in your case the benefit would be less shrinkage and increased durability. I'm not familiar enough with Nason products to recommend an alternate. They make an epoxy called Ful-Poxy that I have used, but I don't know whether it's OK for plastic parts. I have some Sherwin-Williams products that I use sometimes, but the SPI epoxy you mentioned works pretty well for your intended application, and is fairly economical.

Quote:
I am painting everything off the car so i will be painting the jambs too. Is there anything different about spraying epoxy than 2k urethane. Like gun, tip, pressures, requires a more ventilated area, ect.... I tried some polyester primer and that was some really nasty stuff. Burned my eyes and smelled horrible.
Sounds like you are not wearing a good respirator, please make sure you have a good one, there are full face models available to protect your eyes. Epoxy sprays nothing like poly primer, it's more like urethane primer or maybe even a bit like single stage paint. you'll just have to practice a bit to see, it's not too hard. BTW, all painting requires good ventilation! You may want to look into better air movement and a more efficient spray gun if overspray is a problem.

Quote:
If i sprayed the epoxy over the whole car to seal everything and the plastic pieces, how long would i have to wait before i can put the base coat down? and I assume i would have to sand with 400 - 600 prior to base coating??
Waiting until the next day after sealing to paint is usually best with epoxy. You should not need to re-sand, as you will usually have up to 7 days before you need to sand before recoating. You'll want to sand only to knock dirt specks out, and do that with 600 wet. My advice on this is generic, so make sure you get a tech sheet for the product you will use and it should be stated there.
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Old 01-05-2007, 12:47 PM
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ok so i just order some of the spi epoxy primer and will try it. I wish i go it prior to finishing the body, but at least ill use it on thje polyurethane so i think that is the most important part.

Thanks for your help....

Troy
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Old 01-05-2007, 12:52 PM
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SPI epoxy has excellent adhesion and flexibility when applied to these flexible urethane parts. I usually just sand the part then follow up with a red scotchbrite wet followed by a good cleaning with waterborne wax and grease remover. I apply two coats of epoxy and let it cure overnight or up to 7 days, then give the part a light sanding with 600 and shoot paint. I like the texture the sanding and red scotchbrite gives to anchor the epoxy-the adhesion is unbelievable and no need for any adhesion promoters on the urethane plastics. Flexibility is awesome-you can bend the part big time with no risk. The 1K and waterborne flexible parts primers turn brittle and crack and chip easily- some of reconditioned bumpers from the recyclers are having big time problems with this.
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Old 01-05-2007, 08:42 PM
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baddbob is right about urethane parts not needing adhesion promoter. The reason I didn't mention it is because sometimes plastics can be misidentified, and the bulldog won't hurt anything. The easiest way to determine whether promoter is needed is to shave a small piece from somewhere that doesn't show, and put the piece in a container of water, flicking it down a few times to make sure there are no air bubbles hanging onto it. If the plastic floats, it needs adhesion promoter, and if it sinks, save your money and apply the epoxy just as baddbob says.
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Old 01-05-2007, 08:55 PM
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Thanks for the advice really helping...

Well i called the company who makes the parts and they said it is polyurethane: injected polyurethane with silicone base release agents... What ever that means, i dont know. But i tried that float test and when i put a tiny peice in a cap of a soda bottle, it floated, but when i pushed it down with the tip of a pen it stayed down. So what does that mean

So i am going to sand with 400, or maybe 600 and then use scuff it from 3M with a scotch pad.

Not sure about the bulldog stuff. but since i already have it and the manufacture of the parts(cervinis) says they use it, i might just do it.

Then shoot with the spi epoxy.

wet sand then base and ect...

I feel comfortable doing this thants to you guys...

If any problems with that please let me know...
Thanks
TRoy
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Old 01-05-2007, 08:56 PM
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Oh... if my base covers the 400 wet sand scratches, should i use that? I see a lot of people are recommeding 600 instead. I figured the courser the better for adhesion...
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Old 01-06-2007, 07:03 PM
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400 is Ok for solid colors, 600-800 for metalics, or you can go even finer if the epoxy is less than a week old. Just make sure the plastic is good and clean before you shoot that first coat of primer. Scuffing wet helps this alot and using a waterborne wax and grease remover is the only way with cleaning plastic IMO. The epoxy will stay nice and flexible.
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Old 01-06-2007, 07:32 PM
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I recently did a similar bumper cover here was my procedure.


1 Clean surface with a mix of 50%water 50% rubbing alcohol
2 Scuff Surface with a Scotch Brite pad.
3 Clean surface as in step 1 and allow to dry.
4 Using a Tac rag tac surface off.
5 Applied a hybrid epoxy with filling capabilities to the surface, allow to dry.
6 Sand smooth with 320 grit followed by 600.

The Primer used was similar to Valspar DTM200, Its made by 5star P/N 5425

Data on it is available here. No Adhesion promoter is required. It dries fast !

http://www.autobodybrands.com/primers/5425_x2k.html

I think you might be ok with the SEM product, though I have never used it.

BTW, your better off not using W/G remover on Urethane based parts as the
urethane can absorb bi products of the W/G remover which may lead to de-lamination of the primer at a later time.

I attach a pic so you can get an idea of what a covered part looks like .

Best of luck. X711
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