Compatible paints with PP-EPDM plastic

  1. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    A few years ago I painted the rear bumper on my BMW 1 series with spray cans of plastic primer and Cellulose primer over the top of that. I used the primer to fill sanding scratches from previous paint removal. I kept removing the bumper from the car to work on it on a stand. The car was constantly in use so the bumper was always on and off it lots of time’s in between me working on it. In order to remove and refit the bumper I had to flex the sides a little for them to clip on to the bumper retaining clips on the car. After some time of doing this the paint cracked along the areas that required bending to remove and refit.
    PP-EPDM seems to be an awkward material to work with. I tried using a bumper repair filler and it broke off every time I went to sand it. It did this even with keying the surface with 40 grit. In the end I had to make up my own flexible filler out of UPOL quicksand filler mixed 1:1 with UPOL Top Stop Gold polyester body stopper. It has stood the test of time.

    Ive seen a 4:1 high build cellulose primer for sale and it’s said that it works brilliantly on the plastic bumpers of TVR’s. I’m very reluctant to use this now even though it would give brilliant filling capacities compared to cans of plastic filler primer. If I had an air fed mask I would use 2K epoxy, 2K plastic filler primer or something like that. I know that stuff is suitable for plastics.

    So,
    Did the cellulose crack because

    1. It is not flexible for Polypropylene PP+EPDM rubber bumpers. More suitable material on TVR bumpers?

    2. Me taking the bumper on and off repeatedly meant the paint never had time to properly cure and strengthen? If so will an infra red lamp solve this?
    Do I leave the bumper off or on until I’m ready to basecoat it?

    Thoughts?

    Thanks.
     
  2. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    If I emailed BMW they would probably just say. Adhesion Promoter, basecoat then clear.
     
  3. norsa

    norsa old school painter

    Messages:
    1,654
    Location:
    Newbury UK
    You need to start again really. ie take it back to plastic. If you did it in nitro celly, it will wash off.
     
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  4. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    Already done that. I started over fresh with cans of plastic primer and plastic filler primer alone this time. I would have sanded all the plastic really smooth and used adhesion promoter over it but it would have taken an age to remove all the plastic burrs (carpet I call it) and get it smooth again. Multiple cans of plastic primer later and I now have a surface that’s blocked out pretty well aside a few chips. The bumper has been left bolted to the bottom of the car and peeled out of all the top clips to fully uncover all areas of it whilst still attached. It’s been sat that way for months. I’ve recently taken it off to respray the side rear quarter (whatever the technical wording is for that area) portions of the car. Hopefully vast curing time and minimal movement will have prevented any future cracking from occurring. Do you know if Celly is a no no when it comes to bumpers then? It’s never advertised as being for plastics generally. Metal and Glass reinforced plastic are the usual substrates listed. I just had it in my head, years ago, that I needed a plastic primer over any bare areas of plastic merely for adhesion, then I could dump whatever paint I wanted over the top of it. I’m now only half the wiser as to if the cellulose was ever suitable in flexibility as is basecoat/clear coat. As far as the minor chips that are left, I have tried to fill them with Body stopper, only to reach a point whereby, by the time I’ve sanded the edge of the filler flat, the filler in the chipped area has now been lifted out completely. I’m now considering two other polyester products. Either, UPOL Dolphin Glaze or UPOL Reface over these areas as no amount of plastic filler primer ever fills them up. UPOL claim you can bend Dolphin glaze 180 degrees before it snaps. The magic of polyester! In an ideal world I would do what My Friend Pete does in the Diy Automotive School, South West Rod and Custom, American videos on YouTube. Namely the plastic bumper repair segments he’s produced. In that I’d use a flexible polyurethane filler which I can’t find in this country, yet and then shoot 4-5 very heavy wet coats of 2K epoxy primer, which would give me a film thickness the same as the wall of China. Unfortunately I don’t have air fed, yet.... Thanks.
     
    Last edited: May 18, 2020
  5. carbon

    carbon Member

    Messages:
    1,414
    Location:
    S. Glos. U.K
    You can get flexible filler here, I used some when I colour coded the bumpers on my van. Can’t remember who made it now but will check when at work. Used two different makes neither has cracked or flaked off.
     
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  6. norsa

    norsa old school painter

    Messages:
    1,654
    Location:
    Newbury UK
    I cant really advise on using celly and aerosols as im a pro sprayer and not used the stuff in 40 years.
    All I can say is it was superseded because it was unstable even on metal car panels before plastic panels were introduced.
    Best advice. Strip it back to bare plastic and have a word with a spray shop.
     
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  7. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    Cellulose won’t be going anywhere near it then. It was fully stripped back before I started using the plastic primer again. Should be ok this time. I won’t be moving it again until I pop it back on the car and guide coat it again. I’ll spray small amounts of my reface over the tiny chips.
     
  8. steveo3002 Member

    Messages:
    5,231
    cambridge uk
    reface as in polyester spray filler? if so another bad choice
     
  9. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    Yes. I’ve used polyester products on this bumper before and they will not budge or crack. I’ve driven the car for years with polyester. Someone recommended I use dolphin glaze. It is supposed to flex to 180 degrees. I thought it was polyester but it isn’t. What will happen with reface? If I only use it in small patches it would be ok surely. I need a spray or liquid filler. Nothing else will hold in these tiny chips.
     
  10. carbon

    carbon Member

    Messages:
    1,414
    Location:
    S. Glos. U.K
    The two products I used were isopon plastic bumper fill and indasa autofill flex ( from local paint supplier ) this was on a vw T5 front bumper six years ago, so far no signs of cracks. Not sure how much flex there is in the bumper though. Do need to make sure plastic is degreased properly first
     
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  11. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    I’m pretty sure it was the isopon filler I tried years ago. I cleaned the surface with degreaser. Left it to dry. Applied the isopon. Went to sand. Snapped off. Re sanded the area and tried upol adhesion promoter over the area before the filler. Snapped off again.
     
  12. carbon

    carbon Member

    Messages:
    1,414
    Location:
    S. Glos. U.K
    The isopon one I used was black the other is not, but no problems with either

    736EA3AB-E81B-4C8E-97F8-0069E47C5F1A.jpeg
     
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  13. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    Yes. It must all depend on the material. I don’t know what to use on the chips now. It would have to be a very runny material that I can literally just wipe across the surface without tacking to anything unless it’s dry. How fluid like was the Indasa? The body stopper isn’t too bad to apply but it’s a bit sticky like standard filler. If I spot spray one coat of the Reface it’s stupidly high build so I’m hoping, even if Stevo says it’s a mistake using it, it will be flat as hell when it cures so I can sand it like paint and remove all of it apart from a tiny little spec in the chips. It’s in a groove so it’s a sod to fill and sand filler in it. I used a screwdriver in places to scratch off paint from that groove. In some places it dug in. Never again!
     
  14. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    This is it
     
    • 93A6C7A9-5F84-4A49-885C-528A9E891947.jpeg
  15. steveo3002 Member

    Messages:
    5,231
    cambridge uk
    whats wrong with sand the bumper , remove all shody previous work /unsound paint , sand it until its smooth , dust of plastic primer then 2 - 3 coat of 2k high build , sand that smooth and paint it
     
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  16. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    I would very much like to do it that way but I don’t have an air fed mask. I was considering buying an air fed half mask the other day compatible with sata charcoal filters and a second hand sata charcoal filter belt. I could curtain/tarpaulin off my compressor from my spraying area and open the back door to the garage where the compressor is so I get lots of fresh air into it. That and £45-£60 of 2K is a bit pricy for me right now unless there’s a cheaper version of everything apart from stuff from China, which I don’t know for sure will plug into our connectors? I’m not going to spray the bumper right now. Ive got a lot more metal panels to respray first. If I don’t buy anything else for a while then it might be on the cards. Thanks for the reply. I thought you’d left me high and dry. Lol.
     
  17. steveo3002 Member

    Messages:
    5,231
    cambridge uk
    replace 2k primer with epoxy primer then/ or rattle can plastic primer , basecoat and 1k clear , prob what the chipsaway driveway bandits would do

    end of the day the professional products just work , have to accept inferior 1k /rattle can stuff isnt as good and doesnt pretend to be
     
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  18. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    I found out about a non isocyanate 2K epoxy primer. That’s around £45. The manufacturers recommended using air fed with it though. I could shop around for a 1k rattle can epoxy high build. I’ll see what the money situation is when I get around to spraying the bumper. Pro XL super high build grey primer is really good. Much higher build than Tetrosyl cellulose filler primer or upol high build. I’ve asked them a question of whether it will be suitable for my bumper material. If no reply I’ll use it on any areas that I cut through sanding over metal. After the epoxy that is.
     
  19. carbon

    carbon Member

    Messages:
    1,414
    Location:
    S. Glos. U.K
    Epoxy primer is usually non iso
     
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  20. Edward Yemm Member

    Messages:
    97
    Location:
    Forest of Dean, Gloucestershire, England
    Great. So it’s all 2K but safe with a non air fed respirator. If that’s the case Ill find the cheapest, highest building epoxy there is. Something like 4:1. If I can find it.
     
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