PP-EPDM parts

metalman

metalman

Oldtimer
Have some new OEM Mercedes mud flap kits to paint. The plastic is raw PP-EPDM, no primer. Looking for some tips for prep, cleaning, adhesion promoter (that I suspect is need here), etc.
I have Standox base but I use SPI for everything else.
 
pp parts i usually use a grey scotchbrite and some of the scuff gel typ stuff. it really cleans the plastic well. then i just use the spi adpro, activated. 1 coat then its your call if you want to go right to base or prime it. if its got a texture to the plastic you may way to prime first.
 
Do what Jim says, though I always clean with waterborne before the adpro, and always apply at least a sealer between the adpro and the base. But for me, the Standox base has proven to be aggressive enough (wrinkling of fresh sealers, etc.) to make me buy some Standox products specifically for wet-on-wet procedures, specifically their 2K Plastic Primer-Surfacer, which enables me to go directly from bare plastic to base with only one step and no risk of wrinkling or "frying."
 
Thank you for the prep tips. I was thinking of applying a 1:1:1 coat of epoxy after adpro for a sealer, then base.
Black plastic, adhesion promoter, black epoxy, black base...black car. Took a quick look and they look
pretty smooth, they should be for what they cost the customer.
I use SPI reducer and cat in bases but can't remember for beans if I ever shot the Standox over fresh
epoxy sealer.
Do you think the Standox will be too hot with SPI slow reducer? I could go 2 coats epoxy 1:1 and let it be for 18-24 hrs,
wet sand and base.
 
dont do that. anytime you put sealer over adpro and let it 1/2 kick off your lookin for trouble. if you want to do a sealer thats fine but it should be wet on wet. do adpro, sealer then base all one right after the other. one the base is on then let it sit and all the layers harden together.
 
Let us know how it goes. For some reason I was able to get fresh epoxy to fry with a wet coat of Standox base.

I was told it could not happen...it figures I would be the one to make it #*@% up. Murphy loves me.
 
lol crash. yeah whole issue with adpro is its a wet non crosslinked later under a thin hardened layer. adpro wont wrinkle but the 1/2 hardened primer or sealer on top will and it will do it easier because the primer or sealer isnt really bonded to anything thats hard. the adpro will soak up the solvents and reflow again. trick with adpro is to put it on super thin. one fully cover ultrathin coat is all thats needed. anything beyond that and your adhesion actually goes down and you increase the chance of wrinkling whats on top.
 
Finally got to paint the plastic this week. I scuffed thoroughly with the scuff paste, cleaned with water w&gr, one thin coat ad pro, and epoxy 1:1:1 prior to base. Only problem was static which makes the plastic a lint/duct magnet. I painted lots of plastic over the years (not much auto parts), and I find the static goes away after the first coat or two, sand the nerds out. On these parts I didn't want to sand the epoxy and compromise it or the ad- pro so I put two coats of SPI intercoat base activated , let that set a few hours and wet sanded that. It was good after that, base, clear and done. The base wasn't as easy to wet sand as epoxy or 2k but it worked out.
Maybe next time I'll go 2 coats epoxy 1:1 let it be for a day or two then seal with epoxy 1:1:1 prior to paint .
 
If anything I posted doesn't make sense I'll fix it in the near future.
i'm recovering from back surgery and medicated, took 2 days to put tthat last post together.
 
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