Hi all. I modded my hood with a vent and wonder what to seal with prior to primer surfacer. Dupont's plastic adhesion promoter is for use over TPO (Thermoplastic polyolefin) http://www2.dupont.com/Automotive/en_US/products_services/paintCoatings/plasticExterior.html.
My paint store says I must use the promoter but doesn't yet know if it can go over existing paint.

My question is; is a promoter needed over SMC? I have SMC, original paint, hard-set epoxy, and fiberglass resin gel present on this hood. I hope to use a sealer, then primer surfacer. I have seen successful hood vents and wonder how the prep was done.

Next, are the RIM facias made of TPO? Is a promoter needed and can/did it overlap onto original, prepped paint?

Thanks

I'm not sure about the promoter/sealer stuff. But since I just installed a hood scoop as well, I'd like to see the answer.

Regarding the front/rear fasciae, they're made of urethane.

You dont need any kind of ' adhesion promoter'. Just sand till entire surface is dull and prime with regular primer. Sand that and paint. You dont need any ' flex agent ' either. Paint stores are just trying to maximize their sales to non-professionals.

What Roger said.....

Thanks. That makes things simpler. Something else has me a bit worried, however. I just got a plastic repair book and the author stated NOT to use standard polyester fiberglass resin to repair SMC. Says the resins are not compatible. I used a fiberglass resin gel product on some filler pieces on my SMC hood. I think I should grind it out, now, to be safe.

you might get some good info here, www.autobody101.com it has awesome forums for body work and paint. Besides what Roger said, be sure to use a strong wax/remover degreaser (now called surface cleaners or something) BEFORE you do a final overall surface sanding, then use a weaker cleaner (wax remover) before paint. Also dry it off as you go BEFORE it dries or you are not removing the contaminants. YOu will learn all this and much more if you go to this site.... ALso what you read about the fiberglass filler could be verified there...

quote Originally posted by Ratfart: Thanks. That makes things simpler. Something else has me a bit worried, however. I just got a plastic repair book and the author stated NOT to use standard polyester fiberglass resin to repair SMC. Says the resins are not compatible. I used a fiberglass resin gel product on some filler pieces on my SMC hood. I think I should grind it out, now, to be safe.

Interesting....... I used fiberglass to repair two different SMC panels on my 94 Camaro. One area was right next to the passenger side mirror that a chunck was taken out when the mirror was picked off. The other part was at the bottom edge of the front fender. That area is notorious for cracks as many people miss the jacking point on the car and end up cracking the fender. I fixed both areas with the traditional fiberglass resin and cloth. I had the original chunk that had blown out next to the mirror and fiberglassed it from the backside, I did the same thing on the bottom side of the fender, glassing it from behind. I followed up with flexible bumper repair filler, and the rest was standard finishing.

That was several years ago and the repairs still look perfect today. So...... draw your own conclusions.

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Competition Yellow 84 2.5 Bone stock right down to electrical gremlins

I've used standard Bondo brand fiberglass repair stuff and have had no issues with it. I've repaired broken corners on hoods and patched wing holes with the fiberglass, then used regular plastic filler on top of that for finishing.

Mark

Thanks for the input, everyone. The author of How to repair Plastic Bodywork further states on the polyester resin compatability issue "at the very least the repair will become visible underneath the paint, or debond in the worst case". I am going to try to contact him for clarification.

quote Originally posted by Ratfart: Thanks for the input, everyone. The author of How to repair Plastic Bodywork further states on the polyester resin compatability issue "at the very least the repair will become visible underneath the paint, or debond in the worst case". I am going to try to contact him for clarification.

perhaps the reason mine worked so well is that I applied the fiberglass resin and cloth to the backside of the repair, using fleible bumper filler to in order to fill the cracks and imperfections. There is no way the fiberglass even came close to the outer surface. This repair was a structural repair, the #M bumper repair was used on the cosmetic areas. It's a theory anyway.............

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Competition Yellow 84 2.5 Bone stock right down to electrical gremlins